What Water Hygiene and Legionella Control Businesses Sell For in 2026

Updated August 2026 · refreshed quarterly. Next scheduled review: November 2026.

The UK water hygiene and legionella control market is experiencing intense consolidation. Driven by the non-negotiable statutory requirements of the Health and Safety at Work Act 1974, COSHH, and specifically the HSE's ACoP L8 and HSG274 guidance, the sector offers exactly what private equity and strategic acquirers want: mandated, recurring, non-discretionary compliance revenue. Premium regional leaders with £1M+ EBITDA are currently achieving 6.0x to 8.0x EV/EBITDA in competitive processes.

Over the past 24 months, major strategic moves have reshaped the landscape, including Mitie Group's £350M acquisition of Marlowe plc, alongside aggressive bolt-on activity from PE-backed platforms like Phenna Group, andwis, Complii, and Obsequio Group. This guide provides a data-driven framework for valuing UK water hygiene businesses, based on recent transaction evidence and sector multiples.

Contents

1. Why two businesses with the same EBITDA sell for very different multiples
2. The 30-factor valuation framework
3. Sub-niche attractiveness within water hygiene
4. The 2026 EBITDA Multiples Ladder
5. What kills the multiple
6. Regulatory economics: what compliance actually costs and protects
7. Worked examples
8. 2025 and 2026 transactions: United Kingdom
9. 2025 and 2026 transactions: United States
10. The buyer universe: who is acquiring in 2026
11. Demand drivers and regulatory calendar
12. Deal structure: how the consideration is paid
13. Public company multiples
14. The diligence question bank: 25 questions buyers will ask
15. The 12-month preparation timeline
16. FAQ
17. Glossary
18. Methodology and sources
19. About DealFlowAgent
20. Related guides

Why two businesses with the same EBITDA sell for very different multiples

Two water hygiene businesses can report identical earnings and receive offers that differ by several turns of EBITDA. Buyers price the durability of the earnings, not the earnings themselves. The six factor groups below carry the weightings acquirers apply in practice.

Financial (22% weighting)

Deal process and buyer access (22% weighting)

Customer and revenue (16% weighting)

Operations (14% weighting)

People and organisation (13% weighting)

Strategic (13% weighting)

Why the weightings behave this way in practice

The financial and deal-process categories together carry 44% of the scoring weight because they are the two dimensions a buyer can verify quickly and price with confidence. A buyer's corporate finance adviser can pull a debtor ledger and a contract schedule in the first week of diligence, so any weakness there is found early, discounted hard, and rarely negotiated back up. The remaining categories, customer and revenue, operations, people, and strategic accreditation, take longer to verify and are judged more on trend than on a single snapshot, which is why sophisticated sellers start building a track record in each of them a year or more before going to market, as set out in the 12-month preparation timeline.

The commercial logic behind the financial weighting is straightforward: a buyer is purchasing a stream of future cash flow, not a set of historic accounts. Recurring compliance revenue, monitoring contracts, scheduled risk assessments, and temperature checks, all survive an ownership change because the client relationship is with the written control scheme and the accreditation, not with the departing owner. One-off remedial and project work carries no such guarantee. A buyer models the recurring share of revenue as the base case and treats everything else as upside it will not pay for upfront.

Deal process weighting reflects a separate truth that owners often underestimate: value is created by competitive tension, not by the underlying business alone. Two operationally identical businesses can achieve different multiples purely because one was run through a structured process against several PE-backed platforms simultaneously, while the other was sold quietly to the first interested buyer who called. A represented process forces bidders to sharpen their offers against each other, and it also filters out generalist buyers who would price the business on a blended facilities management multiple rather than the regulatory-moat multiple the sector actually deserves.

Customer and revenue concentration matters because a buyer underwriting a purchase price is implicitly underwriting the survival of every material client relationship through the transition. A single client above 25% of revenue is not merely a risk factor on a checklist, it is a veto point: if that client leaves in the first year post-completion, the buyer's investment case collapses. Healthcare and education clients, by contrast, tend to be sticky because switching compliance providers involves its own administrative burden and audit trail, which is why a business with genuine HTM 04-01 healthcare exposure is treated more favourably than one dependent on a single facilities management intermediary that can re-tender the work at will.

Operational and people factors are priced on a simple test: can this business run for 90 days without the current owner answering the phone? A business with high engineer density, integrated scheduling software, and a competent second-tier manager passes that test and is priced as a going concern. A business where the owner personally signs off risk assessments, chases overdue invoices, and manages the three largest client relationships fails it, and is priced closer to a personal service than a company, which is the essence of the owner-dependency discount discussed further under what kills the multiple.

The 30-factor valuation framework

The six-dimension summary above is a useful shorthand, but professional advisers and buyer due diligence teams score businesses against a much finer-grained framework. The 30 factors below are grouped into five categories, adapted for the specific economics of water hygiene and Legionella control: compliance infrastructure, contract stickiness and technician certification depth.

Financial (factors 1 to 6)

Operational (factors 7 to 12)

Regulatory and accreditation (factors 13 to 18)

Market and commercial (factors 19 to 24)

Strategic and exit (factors 25 to 30)

A business scoring predominantly "strong" across the regulatory and financial dimensions is the profile that attracts the 6.0x to 8.0x band on the ladder. A business scoring mostly "weak" and "average", however healthy its headline EBITDA, is priced at the bottom of its size band or excluded from competitive processes altogether.

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Sub-niche attractiveness within water hygiene

Not every water hygiene business is priced against the same yardstick. Buyers hold different views of the sub-niches that sit under the "water hygiene and legionella control" umbrella, and where a target's revenue mix sits across these sub-niches materially affects where it lands within its EBITDA band on the ladder.

Legionella risk assessment and monitoring is the core, statutory-duty activity: written schemes, temperature monitoring, and periodic risk assessment. It is the most recurring and most defensible revenue line in the sector, because it is directly tied to the duty holder's legal obligation under ACoP L8, and it is the line buyers weight most heavily when calculating the recurring-revenue percentage described in the 30-factor framework.

Remedial and project works, tank cleans, system disinfections, TMV servicing, and cooling tower remediation, carry the strongest gross margins in the sector but the weakest recurrence. Buyers value a business that can convert its own risk assessment findings into remedial work in-house, because it captures margin that would otherwise leak to a subcontractor, but they discount a business that is structurally dependent on ad hoc remedial income with no underlying monitoring book to generate it.

In-house laboratory analysis occupies a distinct position. As noted under regulatory economics, UKAS 17025 accreditation is expensive and slow to obtain, which makes it a genuine moat rather than a marketing claim once achieved. Buyers pay a premium for it because it verticalises the value chain: sampling, analysis and remediation recommendation all sit inside the same business, rather than a third-party lab taking a margin slice and controlling the turnaround time the client experiences.

Healthcare and HTM 04-01 work is the most defensible sub-niche by client type. NHS trusts audit their water hygiene providers rigorously, procurement cycles are long, and switching costs are high once a provider is embedded in a trust's estate. A business with genuine, multi-trust healthcare exposure, rather than a single trust relationship, is priced closer to the top of its band because that revenue is judged unlikely to churn at the next contract renewal.

Cooling tower and evaporative system compliance, covered under HSG274 Part 1, is a smaller but growing sub-niche as local authority cooling tower registers are enforced more consistently. Buyers view specialist cooling tower capability as an adjacent-service cross-sell opportunity rather than a standalone value driver, but it supports the "service breadth" factor in the 30-factor framework and reduces a business's reliance on domestic hot and cold water work alone.

IoT and automated temperature monitoring is the sub-niche buyers are most excited about and least able to underwrite on historic numbers alone, because most targets are still early in the transition from manual logbooks. A business with a meaningful base of connected sites earns a qualitative premium for demonstrating technology adoption and for the stickier, software-anchored client relationship it creates, even where the absolute revenue contribution is still modest. Sector context for how this plays across other compliance trades is set out in the compliance, testing and inspection guide.

The practical implication for an owner preparing for sale is that the revenue mix, not just the revenue total, should be actively managed in the years before a process. A business that shifts its mix towards monitoring, healthcare, and in-house laboratory work, and away from single-client remedial project work, moves up its band even if total EBITDA does not change.

The 2026 EBITDA Multiples Ladder

Note: Multiples represent enterprise value to adjusted EBITDA. The lower bound represents an unprepared business sold without competitive tension. The upper bound represents a prepared business, professionally represented, in a competed process.

Reading each band: buyer type, structure and what moves a business up

£250k to £500k (owner-managed / regional), 3.5x to 4.5x. The buyer at this level is typically a private trade acquirer, a slightly larger regional operator, or an individual buyer using bank debt and personal capital, rather than an institutional PE platform. These buyers are acquiring a book of clients and a technician team, and they underwrite heavy owner involvement as a risk they must personally manage post-completion. Structure is dominated by deferred consideration and earn-outs, often 12 to 24 months, because the buyer has no way to verify client retention without living through at least one renewal cycle. To move up a band, an owner needs to demonstrate that the business functions without daily owner input, which typically means appointing an operations lead, converting month-to-month clients to term contracts, and closing any LCA registration gaps well ahead of a process.

£500k to £1M (established SME), 4.5x to 6.0x. Buyers here include larger regional consolidators and the smaller end of PE-backed platforms looking for geographic infill rather than a standalone hub. The owner is usually still central to the business, but a second-tier manager is emerging. Structure blends cash at completion with a meaningful deferred or earn-out component tied to revenue retention, since the buyer's principal underwriting risk remains client flight in the first year. Businesses move up this band by increasing recurring revenue as a share of the total, achieving full LCA registration across the categories the target market actually needs, and reducing single-client concentration below 10% of revenue.

£1M to £2.5M (regional leader), 6.0x to 8.0x. This is the band PE-backed compliance platforms such as Phenna and Complii actively hunt in, because a business of this size can serve as a standalone regional hub capable of absorbing further bolt-ons rather than being absorbed itself. Buyers expect a genuine accreditation moat (LCA plus UKAS where laboratory capability exists), a management team that can run operations without the owner, and clean, defended financials. Structure shifts towards a higher cash-at-completion proportion, and owners are frequently invited, or required, to roll a portion of proceeds into the acquiring platform's equity, aligning them with the platform's future growth. Movement to the top of this band, or into the next one, depends on demonstrating multi-regional coverage and a renewal rate above 90%.

£2.5M to £5M+ (national platform), 8.0x to 10.0x+. At this scale, the buyer universe includes major listed strategics, exemplified by Mitie's acquisition of Marlowe plc, and large-cap private equity funds rather than smaller bolt-on platforms. These buyers are paying for scale, multi-regional or national coverage, and the platform's own capacity to make further acquisitions, so the valuation reflects not just the target's standalone earnings but its strategic value as a base for continued consolidation. Consideration at this level often includes a listed acquirer's shares or a larger equity rollover into a PE-backed platform ahead of a subsequent exit, alongside cash. There is effectively no ceiling within this band beyond what competitive tension between strategic and financial bidders will support; the constraint becomes the quality and defensibility of the earnings rather than the multiple mechanics themselves.

What kills the multiple

• Lacking LCA registration. Legionella Control Association registration is functionally close to a licence to bid on serious contracts. A target without it, or with a restricted category set, has a materially smaller addressable market, because NHS trusts and many local authorities specify LCA membership as a hard tender requirement rather than a preference. Buyers check the LCA register in diligence as a first-day exercise, and a gap here can stall a process entirely while it is remedied. The remedy is straightforward but not instant: commission a pre-assessment, close any non-conformances, and register across every category the target market for the business actually requires, ideally well before a sale process begins, as set out in the 12-month preparation timeline.

• Poor assessment-to-remedial pull-through. Risk assessment generates the remedial pipeline: an assessment identifies deficiencies, and the remedial work fixes them. A target with a large assessment book and no remedial capability is worth less than one that converts its own findings, because it is leaving the highest-margin part of the value chain to a subcontractor or a competitor and cannot prove the pull-through rate a buyer needs to model future revenue. Buyers explicitly test this ratio in diligence, comparing assessments completed against remedial jobs won from the same client base. The remedy is to build or acquire in-house remedial capability, track the conversion rate as a reported KPI, and be ready to evidence it with client-level data.

• Outdated written schemes of control. A well-maintained written scheme with a current asset register creates switching friction, because a client considering a change of provider faces the cost and risk of transferring or rebuilding that documentation. A target whose schemes are out of date has a retention problem it may not have priced into its own valuation expectations, since those clients are the most likely to re-tender at the next renewal. The remedy is a systematic audit of every written scheme against the current asset register, closing gaps before a buyer's technical adviser finds them first.

• Public sector concentration risk. NHS trusts and local authorities dominate many books, and while this client base is defensible in the sense that the underlying statutory duty does not go away, it carries specific risks: procurement cycles expose the contract to periodic re-tender, public sector buyers are price-competitive at that point, and payment terms are frequently slower than commercial clients. A business with public sector revenue above roughly half its book, concentrated in a small number of trusts or authorities, is priced with this risk explicitly discounted. The remedy is not to avoid public sector work, which carries genuine credibility value, but to diversify the client base across multiple trusts, authorities and commercial sectors so no single procurement decision can materially move the business's revenue.

• Blending laboratory revenue. Laboratory analysis has different economics and different accreditation gates (UKAS 17025) than field service work, and blending the two into a single reported margin obscures the true profitability of each. A buyer evaluating laboratory capability wants to see it reported separately, with its own margin, utilisation and accreditation status visible, because a UKAS-accredited lab commands the premium described under regulatory economics only if it can be verified as a genuine, standalone capability rather than a notional add-on to the field service business. The remedy is straightforward management accounting discipline: separate cost centres and separate reporting lines for laboratory and field service revenue well before a data room is assembled.

• Owner-centric client relationships. Where the largest clients deal exclusively with the owner, rather than with an account manager or a named operations contact, the buyer has no verified evidence that the relationship survives a change of ownership. This is one of the most common reasons a business prices at the bottom of its band despite strong headline financials. The remedy is to introduce a second point of contact for every material client well ahead of a sale, so that client familiarity with the wider team, not just the owner, is already established by the time a buyer conducts management presentations.

• Weak documentation of emergency response. Legionella outbreaks, while rare, are high-consequence events, and a business without a documented, tested emergency response protocol looks exposed to a buyer who understands the reputational and legal cost of a mishandled outbreak. The remedy is to formalise the callout procedure, log every historic response, and be ready to walk a buyer's technical adviser through it during diligence.

Regulatory economics: what compliance actually costs and protects

Buyers underwrite water hygiene earnings on the assumption that the regulatory moat is real, current and defensible. The table below sets out the specific accreditation and compliance costs a buyer's adviser will price into diligence, because each one either gates access to contracts or exposes the business to enforcement risk if it lapses.

LCA registration (Legionella Control Association)

The LCA operates a turnover-based annual registration fee structure, broadly comparable to the BPCA model used in pest control. Estimated annual cost runs from £1,500 to £5,000 depending on company size. Initial registration includes a management system review, and annual re-registration requires a documentation check. Re-registration for the 2026/27 cycle is currently open (source: Legionella Control Association).

The commercial consequence of a lapse is severe. A business that loses registration cannot use the LCA logo, is removed from the LCA directory, which is a primary lead source for many operators, and signals non-compliance to the NHS trusts and local authorities that mandate LCA membership as a tender requirement. Buyer diligence should always verify that LCA registration is current and check for any non-conformances or conditions attached to it.

ACoP L8 and HSG274 compliance framework

ACoP L8 is the Approved Code of Practice that forms the legal framework for Legionella control in England and Wales. HSG274, published in three parts, provides the technical guidance covering hot and cold water systems, cooling towers, and other risk systems. Neither document is a certification a business can hold; compliance is instead a legal duty resting on every building owner or occupier.

The HSE enforces this duty through Improvement Notices, Prohibition Notices, and prosecution, with unlimited fines and up to two years' imprisonment available for the most serious breaches (source: HSE, Legionella and Legionnaires' disease). This is the structural reason water hygiene businesses exist at all: building owners must comply, and regulatory tightening translates directly into demand growth. Buyer diligence should test whether the target's service delivery demonstrably meets HSG274 requirements and whether risk assessments are properly documented, because a written scheme that would not survive HSE scrutiny is a liability the buyer inherits on completion.

UKAS accreditation for laboratory testing

Legionella testing laboratories are accredited to ISO 17025 by UKAS. Initial accreditation costs between £5,000 and £15,000, with annual surveillance costing a further £3,000 to £8,000, and the process typically takes six to twelve months to complete. Businesses that control a UKAS-accredited lab command a 0.5x to 1.0x EBITDA premium (DealFlowAgent estimate) because they own the full value chain from sampling through to results, rather than passing that margin to a third-party lab. Where a target claims laboratory capability, buyer diligence should verify the UKAS accreditation number and its precise scope rather than accepting the claim at face value.

SafeContractor, CHAS and Constructionline

Each of these health and safety pre-qualification schemes costs between £200 and £800 per year depending on company size, and each is typically required for access to commercial, NHS and public sector sites. A business without current accreditation across the schemes its target clients require cannot tender for the highest-value contracts in its addressable market. Buyer diligence should confirm all accreditations are current and that renewal dates sit 12 months or more beyond completion, so the buyer is not immediately exposed to a lapse.

Water Treatment Society membership

Membership of the Water Treatment Society costs approximately £200 to £500 per year. It signals technical credibility to sophisticated buyers and clients but is not a mandatory market-access gate in the way LCA registration or SafeContractor accreditation is.

The net effect on valuation

Compliance spend of this order is trivial against the multiple it protects. A business generating £800k EBITDA moving from the discount profile to the premium profile on the ladder is worth roughly £1.2M more in enterprise value, against an accreditation cost measured in the low tens of thousands. This is the single highest-return investment most owners can make in the 12 months before going to market; see the preparation timeline below.

Worked examples

Example 1: the discount profile (£800k reported EBITDA)

A water hygiene business reports £800,000 EBITDA, but is heavily reliant on two FM contracts, uses paper-based logbooks, and lacks full LCA registration.

Step 1: adjustments to reach defended EBITDA. A buyer's quality-of-earnings review typically strips out owner perks and non-recurring items, but also applies a risk discount where revenue quality is weak. In this profile, no addbacks are assumed beyond the reported figure, because the concentration and documentation issues are treated as multiple-suppressing risk factors rather than accounting adjustments.

• Reported EBITDA: £800,000
• Owner remuneration normalisation and one-off addbacks: £0 (none identified; figure already treated as clean)
• Defended EBITDA: £800,000

Step 2: multiple selection. This EBITDA quantum sits in the £500k to £1M band on the ladder, which runs 4.5x to 6.0x. The two-client FM concentration, paper-based logbooks and incomplete LCA registration place the business at the bottom of this range under the 30-factor framework.

• Applied multiple: 4.5x
• Enterprise value: £800,000 × 4.5 = £3,600,000

Step 3: the equity value bridge. Enterprise value is not the amount the owner receives. A buyer deducts net debt and adds back any surplus cash, then adjusts for a normalised level of working capital agreed in the sale and purchase agreement.

Of this, a meaningful proportion is likely to be structured as deferred consideration or an earn-out over 12 to 24 months given the concentration risk, reducing the cash received at completion below the headline equity value figure; see the deal structure section.

Example 2: the premium profile (£800k reported EBITDA)

A water hygiene business reports the same £800,000 EBITDA, but with 75% recurring compliance revenue, full LCA registration, UKAS 17025 laboratory accreditation, and proprietary compliance software.

Step 1: adjustments to reach defended EBITDA. The quality-of-earnings review here confirms the reported figure is genuinely recurring and well-supported by contract documentation, so no downward risk adjustment is applied, and a small addback is identified for a one-off legal cost incurred during the year.

• Reported EBITDA: £800,000
• Addback: one-off legal cost unrelated to ongoing operations: £15,000
• Defended EBITDA: £815,000

Step 2: multiple selection. This EBITDA quantum again sits in the £500k to £1M band. The strong recurring revenue mix, full LCA registration, in-house UKAS-accredited laboratory, and proprietary software place the business at the top of the range.

• Applied multiple: 6.0x
• Enterprise value: £815,000 × 6.0 = £4,890,000

Step 3: the equity value bridge.

The two examples share an identical starting EBITDA, yet the equity delivered to the owner differs by roughly £1.45M, driven almost entirely by revenue quality, accreditation completeness and documentation discipline rather than by any difference in headline earnings. This is the practical demonstration of the principle set out at the top of this guide: buyers price the durability of the earnings, not the earnings themselves.

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2025 and 2026 transactions: United Kingdom

Note: the £350M Mitie acquisition was for the entire Marlowe group. Marlowe's Water & Air Hygiene segment reported £170M annual revenue. The implied EV/EBITDA for the whole group was approximately 10.7x to 11.2x.

2025 and 2026 transactions: United States

The buyer universe: who is acquiring in 2026

The table below sets out the active buyer types by geography, the target size each typically pursues, and the consideration structure they tend to favour. Owners preparing for a sale should map their own EBITDA and profile against this table before assuming a particular buyer type is realistic; a £600k EBITDA business is not a credible target for Mitie, and a £4M national platform is unlikely to attract a small regional bolt-on buyer.

United Kingdom

• Mitie Group. Strategic (listed). Transformed the market with the £350M acquisition of Marlowe plc, bringing WCS Group in-house.
• Phenna Group. PE platform (Oakley Capital). Acquired Aquatech Environmental Services in September 2025.
• andwis Group. PE platform (H.I.G. Capital). Acquired IWS Water Hygiene in March 2026.
• Complii. PE platform (Ansor Capital). Acquired Sweetbriar Limited in July 2026.
• Obsequio Group. PE platform (Warren Equity Partners). Acquired Clear Flow Water Treatment in April 2026.

United States

• Solenis. PE platform (Platinum Equity). Completed the major NCH and Chem-Aqua transaction in November 2025.
• Ecolab and Nalco. Strategic (listed). Acquired Ovivo Electronics UPW in December 2025.
• ChemTreat. Part of Veralto (listed).

Matching a target business to the right buyer type is as important as achieving the right multiple: a business sold to a strategic buyer at the wrong stage of readiness, or to a PE platform that already has a competing regional hub, can leave value on the table regardless of the headline multiple agreed. Get your free buyer list to see which of these buyer types is actively acquiring businesses that match your profile.

Demand drivers and regulatory calendar

The commercial appeal of water hygiene to buyers rests on one structural fact: demand is created by statute, not by discretionary client budgets. Every instrument below is a legal duty on a building owner or occupier, which means the market does not contract in the way discretionary facilities spend does during a downturn. Buyers underwrite this by pricing the sector closer to a compliance annuity than to a conventional services business, and the calendar below is what a buyer's commercial adviser will reference when testing that assumption in diligence.

• ACoP L8 (4th edition, 2013). The approved code of practice for the control of legionella bacteria in water systems. The foundational document driving UK market demand, and the reference point against which every UK water hygiene business's methodology is judged, as discussed under regulatory economics.
• HSG274 Parts 1, 2 and 3. Technical guidance covering evaporative cooling, hot and cold water, and other risk systems. A business that can evidence its service delivery meets HSG274 in full, not just ACoP L8 in outline, is in a stronger diligence position because it demonstrates depth rather than a minimum compliance posture.
• HTM 04-01. The NHS estates standard. Determines what a healthcare-weighted contract book actually requires, and underpins the healthcare contract premium referenced under sub-niche attractiveness and in the FAQ below.
• ASHRAE Standard 188-2021. Minimum legionellosis risk management requirements for US building water systems. Relevant to buyers assessing US targets or UK platforms considering transatlantic expansion, and a reference point for the US transaction activity tracked in this guide.
• CMS QSO-17-30. US federal Medicare requirement for healthcare facilities to have water management plans. Functions in the US market similarly to HTM 04-01 in the UK: it creates a defensible, procurement-driven healthcare sub-market.
• 10 NYCRR Part 4. New York State regulation; the strictest state regime, requiring cooling tower registration and sampling. Illustrates the trend towards more prescriptive, locally enforced requirements that buyers increasingly view as a leading indicator for what other jurisdictions will eventually adopt.

None of these instruments are static. Regulatory tightening, whether through updated HSE guidance, expanded NHS estates requirements, or new US state-level cooling tower registers, tends to expand rather than contract the addressable market for compliant operators, because it raises the bar that unregistered or under-resourced competitors cannot clear. This is one reason buyers treat regulatory change as a demand tailwind rather than a risk in this sector, in contrast to industries where tightening regulation raises costs without expanding revenue opportunity. See the fire safety guide and the compliance, testing and inspection guide for how the same dynamic plays out across adjacent statutory compliance trades.

Deal structure: how the consideration is paid

In the current market, smaller water hygiene bolt-ons (£500k to £1M EBITDA) typically see consideration structured as cash at completion, supplemented by deferred consideration or an earn-out over 12 to 24 months. These earn-outs are usually tied to revenue retention or EBITDA targets, protecting the acquirer against client flight.

For larger businesses (£1.5M+ EBITDA) acquired by PE-backed platforms such as Phenna or andwis, owners are frequently offered, or required, to roll over a portion of their equity into the acquiring platform. This aligns the owner's interests with the platform's growth and offers a second bite of the apple upon the platform's eventual exit. Working capital is typically settled on a completion accounts basis, though locked-box mechanisms are increasingly used for smaller deals to reduce post-completion friction.

Consideration structure by size band

The pattern across the table is consistent with the logic set out throughout this guide: the smaller and less prepared the business, the more the buyer needs a period of live trading to verify that client relationships and earnings survive the change of ownership, and the more consideration is deferred to fund that verification. A well-prepared business that has already done the work described in the 12-month preparation timeline can shift meaningfully further towards cash at completion within its size band, even before it moves up to the next band's higher multiple.

Earn-out triggers specific to water hygiene contract retention

Earn-out mechanics in this sector are rarely generic revenue or profit targets. They are typically built around the specific risk a water hygiene buyer is most exposed to: the loss of contracted monitoring and risk assessment clients in the first 12 to 24 months after completion, when the relationship transition from outgoing owner to acquiring business is at its most fragile. Common triggers include:

• Contract renewal rate. The percentage of contracted clients, measured by value, that renew at their next scheduled renewal date following completion. A threshold below 85% to 90% typically reduces or eliminates the earn-out payment, since it signals the retention risk the buyer priced for has materialised.
• Named key-client retention. Specific named clients above a materiality threshold, often the largest three to five accounts, must remain under contract at agreed terms through the earn-out period. Loss of a single named client can trigger a proportionate clawback even where the aggregate revenue target is otherwise met.
• LCA registration and accreditation maintenance. Continued LCA registration, and maintenance of any UKAS laboratory accreditation, through the earn-out period, since a lapse would undermine the very moat the buyer paid a premium for.
• Technician retention. Retention of the LCA-registered technicians named in diligence, recognising that client relationships in this sector often sit with the individual engineer conducting the site visit as much as with the corporate brand.
• EBITDA or revenue threshold, adjusted for the buyer's own investment. Where the acquiring platform invests in shared services, rebranding, or systems migration during the earn-out period, the target is typically adjusted to exclude the cost or disruption of that integration, so the seller is not penalised for the buyer's own strategic decisions.

Owners should negotiate earn-out definitions with the same rigour they apply to the headline multiple, because a poorly drafted retention definition, for example one that does not account for a client's own insolvency or a genuine, documented service failure unrelated to the transition, can convert what looks like a strong headline price into a materially lower outcome. Specialist advisers who have negotiated water hygiene earn-outs before are best placed to close these gaps; see exit planning for how to sequence this alongside the wider preparation process, or book a confidential call to discuss a specific structure.

Public company multiples

Note: public company multiples are sentiment markers only. There is no direct read-across from these global, diversified entities to private lower mid-market transactions.

• Veralto (NYSE: VLTO). Parent of ChemTreat. Water Quality segment reported approximately $3.3B revenue with 22.6% to 24.6% operating margins in 2025.
• Ecolab (NYSE: ECL). Water segment represents approximately 49% of revenue.
• Mitie Group (LSE: MTO). Facilities compliance group, now owner of Marlowe and WCS Group. Trades around 12x to 14x EV/EBITDA.

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The diligence question bank: 25 questions buyers will ask

Owners who prepare answers to these questions before going to market shorten the process, reduce the risk of price chipping, and demonstrate the operational maturity that supports a premium multiple. The 25 questions below are grouped as a buyer's advisers would structure them.

Financial (questions 1 to 5)

1. Provide a contract-by-contract revenue schedule showing client name, annual value, contract start date, renewal date, notice period, and any price escalation clauses.
2. What is the split between recurring contract revenue (monitoring, risk assessments, ongoing management) and project or remediation revenue (tank cleans, system disinfections, one-off assessments)?
3. What is the gross margin on recurring contract work versus remediation and project work, and how has this changed over three years?
4. What is the average revenue per technician per day, and how does utilisation compare to industry benchmarks (target range: 75% to 85%)?
5. Provide an aged debtor analysis. What percentage of invoices is paid within 30 days, and what is the bad debt write-off history?

Operational (questions 6 to 10)

1. List every LCA-registered technician by name, registration number and expiry date. Which hold additional qualifications, such as City & Guilds 2760 or BOHS P901/P902?
2. What compliance and scheduling software is used? Can the business demonstrate automated certificate generation, overdue-visit alerts, and client portal access?
3. How many Legionella risk assessments are conducted per month, what is the average time per assessment, and what is the re-assessment cycle (should be every two years, or on material change)?
4. What is the emergency callout procedure for suspected Legionella outbreaks, and how many outbreak responses have been handled in the last three years?
5. Describe the sampling process: who collects samples, how are they transported, which laboratory processes them, and what is the turnaround time for results?

Regulatory (questions 11 to 15)

1. Provide the current LCA registration certificate, the last annual assessment report, and any conditions or non-conformances raised.
2. Provide SafeContractor, CHAS and Constructionline certificates with expiry dates, and disclose any failed assessments in the last three years.
3. Where the business operates a testing laboratory, provide the UKAS accreditation certificate, the scope of accreditation, and the last surveillance visit report.
4. Has the business ever been involved in a Legionella outbreak investigation by the HSE or a local authority? Provide details and the outcome.
5. Provide evidence that risk assessments are conducted in accordance with ACoP L8 and HSG274, including sample reports, methodology documents and QA procedures.

Commercial (questions 16 to 20)

1. List all NHS Trust, local authority and housing association contracts, with value, term, KPIs, and any penalty clauses for missed visits or late reporting.
2. What has the contract renewal rate been for the last three years, and list any contracts lost together with the reason.
3. What is the customer acquisition cost and what are the primary lead sources (LCA directory, referrals, tenders, website)?
4. Does the business offer IoT or automated temperature monitoring? If so, how many sites are connected, what is the monthly recurring revenue, and which platform is used?
5. What adjacent services are offered, such as HVAC maintenance, fire risk assessments or air quality testing, and what percentage of revenue do they represent?

Legal and compliance (questions 21 to 25)

1. Provide all standard terms and conditions, service level agreements and template contracts. Are any contracts exposed to unlimited liability?
2. Provide professional indemnity, public liability and employers' liability certificates, and disclose any claims in the last five years.
3. List all vehicles and specialist equipment, including sampling kits, temperature probes and dosing equipment, noting owned versus leased status, age and replacement schedule.
4. Are there any ongoing disputes with clients, HSE investigations, or pending litigation?
5. Provide staff contracts for all key personnel, including notice periods, restrictive covenants, and any retention arrangements already in place.

Owners preparing a data room should map each of these 25 questions to a document before engaging an adviser. A gap here is not fatal, but it is a delay, and delay in a competitive process erodes the negotiating position that built the tension in the first place.

The 12-month preparation timeline

Multiple uplift is built, not negotiated. The sequence below sets out what a well-advised owner should be doing in each phase of the year before going to market, aligned to the 30-factor framework and the regulatory economics above.

Months 12 to 10: compliance foundation

• Commission an independent LCA pre-assessment to identify and fix any non-conformances before buyer due diligence begins (estimated cost: £1,000 to £2,000).
• Ensure every technician's LCA registration is renewed and current.
• Achieve SafeContractor and CHAS accreditation if not already held; these are table stakes for NHS and local authority tenders.
• Begin documenting every risk assessment in a standardised digital format, rather than handwritten notes.
• Audit the ACoP L8 compliance methodology and confirm it would withstand HSE scrutiny.

Months 9 to 7: revenue quality

• Convert month-to-month clients to 12 to 24 month contracts with auto-renewal and 90-day notice periods.
• Increase recurring revenue as a percentage of total, targeting 75% or more from contracts rather than one-off projects.
• Win at least one NHS Trust or large housing association contract, which proves institutional credibility to a buyer.
• Implement or upgrade compliance software with a client portal, automated scheduling and certificate generation.
• Begin building IoT and automated monitoring revenue if not already offered; even 20 connected sites adds recurring revenue and supports a technology premium.

Months 6 to 5: operational independence

• Reduce owner involvement in site visits to zero; the owner should not be a technician by the time the business goes to market.
• Appoint or formalise an operations manager who owns scheduling, quality and client relationships.
• Ensure at least three LCA-registered technicians, excluding the owner, so the buyer can see the capability survives owner exit.
• Document every process: risk assessment methodology, sampling procedures, emergency response protocol, and QA checks.
• Pursue ISO 9001 if not already held; this is a six-month project and should start at month 10 if it is being pursued.

Months 4 to 3: financial preparation

• Engage an accountant to prepare normalised management accounts, stripping out owner perks and one-off costs.
• Calculate defended EBITDA with contract-level detail supporting every material line.
• Prepare a contract schedule showing renewal dates, values and client tenure.
• Get a professional valuation or an indicative range from an M&A adviser; see our free valuation calculator for an initial estimate.

Months 2 to 1: market readiness

• Prepare a CIM or engage an adviser to run the process for you.
• Brief key technicians on retention; buyers will want LCA-registered staff tied in with 12-month notice periods or retention bonuses.
• Ensure every accreditation has 12 months or more remaining before its next renewal.
• Assemble the full data room: three years of accounts, the contract schedule, LCA certificates, technician qualifications, insurance documents, the vehicle schedule, the client list with revenue per client, and sample risk assessments, mapped directly to the diligence question bank above.

Owners who work this sequence in full typically move from the bottom of their EBITDA band to the top of it, which on a £800k EBITDA business is the difference between the discount and premium worked examples above, a swing of roughly £1.2M in enterprise value.

Frequently asked questions

What is the average EBITDA multiple for a UK water hygiene business?

A typical established SME generating £500k to £1M EBITDA sells for between 4.5x and 6.0x EV/EBITDA. Regional leaders with £1M to £2.5M EBITDA command premium multiples of 6.0x to 8.0x. Owner-managed businesses at £250k to £500k of earnings sit at 3.5x to 4.5x, usually with meaningful deferred consideration. The full ladder lists every band with enterprise value ranges.

How does LCA registration affect valuation?

Legionella Control Association registration is a critical value gate. Buyers view it as a licence to operate. Businesses with full registration across multiple categories command higher multiples because their addressable market is larger and more defensible.

Who are the main buyers of water hygiene companies?

The market is currently dominated by private equity-backed compliance platforms executing buy-and-build strategies. Key players include Phenna Group, andwis Group, Complii, and Obsequio Group, alongside strategic giants like Mitie. The buyer universe section sets out who is active at each size.

What proportion of revenue should be contracted before I go to market?

Water hygiene is bought as a compliance annuity, so contracted monitoring, sampling and remedial revenue is what the multiple is paid on. Businesses whose earnings rest on ad hoc project work or one-off remedial jobs price at the bottom of their band, because the buyer cannot underwrite the revenue repeating next year.

Does the sector's regulatory calendar support demand?

Yes. Legionella risk assessment, monitoring and remedial work are driven by statutory duties under ACOP L8, not by discretionary spend, which is why compliance platforms treat the sector as base-load revenue. The demand drivers section covers the 2026 position.

How is the consideration usually structured?

Below roughly £1M of EBITDA, expect a meaningful proportion of deferred consideration or earn-out, because buyers are pricing the risk of client flight after the owner leaves. Larger regional leaders achieve a higher cash-at-close share and, at platform scale, equity rollover. The deal structure section explains the split.

What is my water hygiene business worth if the owner still holds the client relationships?

Less than the ladder suggests. Owner dependency is the most common reason a business prices at the bottom of its band: the buyer is acquiring a job rather than a company, and the risk of client flight caps the multiple. Removing the owner from day-to-day client contact is usually worth more than a year of revenue growth.

Which other compliance guides are relevant to a water hygiene sale?

Most water hygiene buyers are multi-discipline compliance groups, so the pricing read-across matters. See the testing, inspection and certification guide, the fire safety guide and the maintenance contracts guide, alongside the water hygiene sector page. The full library of valuation guides is a useful reference point if you are benchmarking against an adjacent trade.

Does LCA registration need to cover every category, or just the categories I currently trade in?

Buyers look at both the categories a target currently holds and the categories it could plausibly add without material investment. Registration restricted to a single category, such as risk assessment only, caps the addressable market to that service line and signals to a buyer that the business has not made the modest additional investment needed to compete for wider scopes of work. Full registration across risk assessment, monitoring, remedial and, where relevant, water treatment categories widens the pool of contracts the business can bid for post-acquisition, which is precisely what a buyer is paying the premium multiple to acquire. Owners planning a sale should review their LCA category coverage against the categories their target buyer's existing platform businesses hold, since a gap that limits cross-selling into the platform's existing client base is a specific, fixable point buyers will raise.

Is an in-house laboratory worth building before a sale, or is it too late to matter?

The economics depend on the runway available. UKAS ISO 17025 accreditation, as set out under regulatory economics, typically takes six to twelve months and costs £5,000 to £15,000 to establish, with £3,000 to £8,000 in annual surveillance thereafter, against an EBITDA premium of 0.5x to 1.0x once genuinely established and verifiable. An owner with 18 months or more before a planned sale can usually justify starting the process, particularly if sample volumes already support in-house analysis economically. An owner with under six months of runway is generally better advised to focus preparation effort on the factors described in the 12-month preparation timeline that can be completed and evidenced in that window, since a laboratory accreditation started but not completed by the time of a process demonstrates intent without yet delivering the verifiable moat a buyer will pay for.

Why do healthcare-weighted contract books attract a premium, and how large is it?

Healthcare contracts, particularly those governed by HTM 04-01, carry a premium because NHS trusts conduct rigorous provider audits, run long procurement cycles, and face high switching costs once a provider's documentation and service history are embedded in their estate records. This guide does not assign a specific numerical premium to healthcare concentration in isolation, because the effect is captured within the broader "customer and revenue" weighting in the 30-factor framework and within the sub-niche discussion above. In practice, a business with genuine multi-trust healthcare exposure, rather than dependency on a single trust, is priced towards the top of its EBITDA band because the buyer judges that revenue least likely to be lost at the next contract renewal.

When is the right time to sell a water hygiene business?

The right time is a function of the business's own readiness against the 30-factor framework, not of macro market timing alone, although the current wave of PE-backed consolidation described throughout this guide means buyer appetite and competitive tension are both elevated. Owners closest to retirement, or facing a specific triggering event, should begin the 12-month preparation timeline as soon as a sale becomes a serious consideration, since most of the value uplift available comes from work completed well before a process starts, not from timing the announcement of a sale to coincide with a particular month or quarter. Waiting for a marginally better market backdrop while ignoring an LCA registration gap or unresolved client concentration is usually the wrong trade.

What actually happens in a first conversation with a buyer or adviser?

A first conversation is exploratory and confidential, and should not require the owner to disclose sensitive client or financial detail before any engagement is agreed. A credible adviser will typically ask for a broad picture of EBITDA, revenue mix between recurring and project work, accreditation status, and the owner's own timeline and objectives, then use that to give an indicative view of which band on the ladder the business is likely to sit in and what preparation, if any, would move it up. It is also the point at which a free valuation estimate or an initial buyer list is most useful, since it grounds the conversation in evidence rather than assumption. Owners considering a sale in the next one to three years are best served by having this conversation early rather than waiting until they are ready to transact; see exit planning for how to sequence it, or book a confidential call to start one.

Glossary

Methodology and sources

This guide triangulates private market multiples using published TIC sector data (including Baker Tilly's 2026 TIC sector report and MAInsights platform data) and the implied ceiling established by Mitie's £350M acquisition of Marlowe plc. DealFlowAgent estimates are explicitly labelled. All transaction data is restricted to 2025 and 2026 announcements.

About DealFlowAgent

DealFlowAgent is a specialist sell-side M&A advisory firm. We protect the legacies of owner-led businesses in the building services and healthcare sectors. If you advise owners in the water hygiene or broader testing, inspection and compliance trades, we partner with solicitors and accountants to manage the M&A workstream. Visit our advisers page for details.

Related guides

• Fire Safety Valuation Guide
• HVAC Valuation Guide
• Electrical Contractor Valuation Guide
• Security Systems Valuation Guide
• Compliance, Testing & Inspection Valuation Guide

Disclaimer: this guide provides general market information and does not constitute financial or legal advice. Every business is unique, and valuations depend on specific operational and financial circumstances.

Related sector pages and valuation guides

Sector pages for this trade

• Water hygiene and legionella control M&A
• Testing, inspection and certification M&A

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Joining full-time on 22 August 2026 from the largest M&A advisory firm in the UK, owned by K3 Capital. As an ex-Director he managed teams of M&A advisors, analysts and associates, working daily with business owners, buyers and stakeholders on live acquisition deals. Selected from 260 applicants alongside colleagues from investment banking backgrounds, he brings that experience and network to lead the advisory bench across Building Services, Facilities Management, and Healthcare.

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Martin is one of the most well-connected figures in UK fire, security, building services and FM. He is Chairman of both the Fire Industry Association and the British Security Industry Association, the only person in the UK to hold both roles simultaneously. Martin spent over a decade in senior leadership at Mitie, latterly as Industry Liaison Director for its fire and security division, helping scale the business past £500m in revenue and playing a role in the £366m acquisition of Marlowe plc, which created one of the UK's largest compliance, fire and security services groups. He joined DealFlowAgent because owners in these sectors deserve a genuine sector-specialist advisor across valuation, business optimisation and buyer access. In recognition of his industry roles, he acts in a personal, non-partisan capacity.

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Nick leads FM Talent Partners, the facilities management and real estate leadership search firm, and is a leading specialist in building services and FM management talent. He partners with DealFlowAgent on two-way referrals: helping business owners and acquirers fill the key roles that decide whether a business is sellable, and introducing owners who are thinking about their next chapter to a team that knows their industry and their market. Key-person dependency is one of the two most common reasons a sale collapses, and Nick fixes it at source.

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• •17 completed M&A transactions over the past six years across UK SME fire safety, security and compliance-led services
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• •Information request lists, databook prep, IC-style summaries and EV-to-equity bridge work
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• •22 completed M&A transactions
• •Direct relationships with hundreds of strategic and financial acquirers
• •Previously built a mobility and field services business to 30 staff and 6 UK warehouses, then sold via competitive process with an EY M&A partner
• •Raised £2m in funding; placed 3rd of 1,900 at OnStage (the "Y Combinator of Europe")
• •Full-stack developer of advanced agent systems and second-brain tooling for the M&A process

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