Adding a second service line without wrecking your margin

Every established legionella firm reaches the same fork. The risk assessments and monthly monitoring are ticking over, the engineers have gaps in their diaries, and the obvious move is to sell more to the sites you already hold. Closed systems, cooling towers, TMV servicing, tank cleaning: all sit next door to what you already do. The mistake is choosing between them on how much you fancy the work. Sort them by revenue shape first.

There are two shapes. Recurring work bills on a cadence and renews on its own, so it stacks on top of your existing monitoring book and compounds. Project work pays once, handsomely sometimes, then leaves you hunting the next job to stand still. A firm that grows only through projects is running up a down escalator: strong months followed by a scramble. The lines worth adding first are the ones that behave like your monitoring contracts, because those raise the value of the whole business rather than this quarter's revenue alone.

We have argued that you should price each line from asset count and your own costs. The same discipline decides which lines are worth having at all.

Closed systems: two revenue shapes in one discipline

Closed heating and chilled systems are the clearest illustration, because the discipline splits neatly down the recurring/project line. BSRIA BG29 pre-commission cleaning is one-off project work: you clean and flush a new or refurbished system once, before it is handed over, and then you are done. Good money, real skill, but each job ends. BG50 ongoing sampling and treatment is the recurring half, periodic sampling and dosing to keep the closed system's water within spec, commonly on a quarterly rhythm.

If you can only chase one, the recurring half is what compounds against your existing book. BG29 is worth doing when a commissioning job lands in your lap, but a business plan built on it is a business plan built on winning new installs forever. BG50 renews.

TMV servicing: small ticket, high frequency

Thermostatic mixing valves need periodic servicing: strip, clean, descale, disinfect, check the failsafe. Healthcare runs them at six-monthly intervals, and the TMV2/TMV3 servicing regime keeps demand steady wherever scald protection is mandated. The ticket per valve is small. Figures around £250 to £300 per service are cited commonly, though what you actually charge depends on volume and access.

The economics only work through route density. One TMV service is barely worth the drive. Forty valves across a hospital wing, booked against a site you already visit for monitoring, is a good half-day that renews twice a year. TMV work rewards firms that already have the site, which, if you hold the monitoring contract, is you. That is the pattern to look for: a new line that rides on visits you are already making.

Cooling towers: the line with a legal gate

Cooling towers and evaporative condensers are the highest-value adjacency and the one that bites the unprepared. They carry a compliance gate the others do not. Every tower is notifiable to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, and running one outside that regime is a criminal matter, not a paperwork slip. Applying biocide competently is its own barrier: get the dosing wrong on a tower and the failure mode is an outbreak, not a warm tap.

None of that means avoid towers. It means do not diversify into them blind. The competence and the liability are the reason the work pays, because a client is buying reassurance that you will not put them in front of the HSE. If your engineers are not yet trained and insured for tower work, the honest sequence is training and cover first, contracts second. Reverse it and the first bad tower is uninsurable.

Tank cleaning and the general rule

Cold water storage tank cleaning and chlorination sits closer to the project end. It is periodic, but it is heavier on kit and access than on cadence, and it often surfaces as remedial work off the back of a tank inspection you already do. It is a natural upsell rather than a standalone book, worth adding for the margin on work you are already recommending, not as the plank of a growth plan.

Behind all four sits the same rule. Each line carries its own gate, whether competence, kit or liability, and the gate is what protects the premium. Anyone can undercut you on a service that needs no accreditation. The lines where a client has to trust you are the lines where you can hold price. Diversify toward the gates you can credibly clear, and let the ungated commodity work go to whoever wants it cheapest.

Why clients are pushing you toward this anyway

There is a pull as well as a push. Duty holders increasingly want a single accountable provider across all their water activities rather than four contractors blaming each other when a sample fails. If you hold the legionella contract and someone else does the closed systems, you are one review away from losing both to whoever offers the lot. Consolidation cuts toward the firm that can carry the whole scope. That is an argument for widening, provided you widen into recurring lines with gates you can clear, rather than bolting on project work to look bigger. If that wider scope reaches you through a facilities management company, read the evidence and payment clauses before you sign, because the small print on FM subcontracts is its own trap.

The operational catch is that every new line is another cadence to run, another set of assets to track, another stream of visits and invoices that has to not fall through the cracks. Add cooling towers and you have added quarterly sampling, biocide records and a notifiable asset register on top of everything you already run. A new line deserves the same disciplined start as a new contract: survey the assets, build the register, then schedule, the sequence we set out in mobilising a new contract. The first missed tower sample undoes the reason the client consolidated with you.

BlueWave was built so a new line becomes recurring visits against real assets rather than a new spreadsheet. A BG50 dosing round, a six-monthly TMV service, a quarterly tower sample: each is a recurring job on the scheduler, itemised on the contract billing so the new line invoices alongside the monitoring book instead of in a separate ledger you reconcile by hand. When you take on a second service line, the paperwork load is the part that quietly sinks it. Keeping it in the same place as the first is how the margin survives contact with a fourth cadence.

Before you add anything, run one test on the candidate. Does it renew without you selling it again, and can you clear its gate? Two yeses is a service line. One yes is a project you should price as a one-off and not build a plan around. No yeses is somebody else's job.