Walk into most shops and the water risk looks trivial: a staff kitchen tap, a customer toilet, maybe a cleaner’s sink. No wards, no spa, no swimming pool. That first impression is exactly why retail Legionella is so easy to get wrong. In shops and shopping centres the danger rarely sits in the obvious fittings — it hides in the gaps. The unit that stood empty for four months. The pipe nobody is sure who owns. The cooling tower on the roof that “the facilities lot deal with”.

So this is less about plumbing and more about blind spots. Below are the mistakes that catch retail and centre management teams out, and what to do instead. Most cost very little to fix once you can actually see them.

The mistakes that quietly undo retail water safety

None of these are exotic. They are the ordinary ways a busy retail operation loses sight of its own water system.

Assuming “no showers” means “no risk”

Showers get all the attention because they fire warm water straight at a person as a fine spray. Shops often have none, and managers reasonably conclude the risk is negligible. The conclusion is wrong, because plenty of other retail kit produces a breathable mist: spray taps in staff and customer washrooms, vegetable misters over fresh produce, decorative fountains and water walls in malls, garden-centre irrigation and plant-misting lines, and any cooling tower serving the building’s air conditioning. Legionnaires’ disease is contracted by inhaling contaminated droplets, not by drinking the water [5], so the question is never “do we have showers?” — it is “where does this building turn water into a mist, and who breathes it?” HSE’s list of the systems most likely to create risk is the right thing to sense-check your own site against [3].

The fix: walk the building and write down every point that can generate spray or aerosol, then treat those as your priority outlets — not the bucket-filling taps.

Letting void units sit on live water systems

In a shopping centre, units turn over constantly. A unit can sit empty for months between tenants with its water supply still charged — full pipes, a dead tap, warm still water sitting at retail-floor temperature. Then a new tenant fits out, opens a tap that has not flowed since spring, and the first thing through it goes into a sink, a coffee machine, or a food-prep area. Stagnation is the single biggest driver of Legionella growth, and a void unit is stagnation by default.

The fix: treat a vacant unit as a managed state, not a pause. Either isolate and drain the supply, or keep it on a logged flushing routine, and recommission it deliberately — flush through, check temperatures, record it — before anyone reoccupies.

Nobody owning the pipe between landlord and tenant

This is the structural flaw that multi-let retail has and a standalone shop does not. The lease splits the building into demised parts (the tenant’s unit) and common parts (the landlord’s risers, tanks and plant). On paper that looks tidy. In practice the run of pipe from the landlord’s riser to the tenant’s first fitting is precisely the stretch each side assumes the other manages. The duty to control Legionella does not vanish into that gap; the duty holder for each part stays accountable, and contracting the work out does not move the accountability [1].

The fix: lay the water system over the lease plan and put a name against every section — landlord or a named tenant. The length nobody claims is where you start.

Building a dead leg at every fit-out

Retail churn means constant refits. When a unit is stripped out, the quick option is to cap the redundant pipework at the wall and move on. Do that a dozen times across a centre and you have a dozen dead legs — short blind branches holding warm, still water that feeds nothing and gets flushed by nothing. Each one is a small incubator wired into your live system.

The fix: when a fitting is removed, take its pipework back to the live main rather than capping it close to where it used to serve. It costs a little more on the day and removes a risk you would otherwise carry indefinitely. Complacency in Legionella control covers how small omissions like this accumulate into real exposure.

Treating the cooling tower as “facilities, not water safety”

Large stores and covered centres often run cooling towers or evaporative condensers as part of their air conditioning. These are the highest-risk water systems on most sites: they generate a fine aerosol and can disperse it well beyond the building footprint. They also carry a specific legal duty — cooling towers and evaporative condensers must be notified to the local authority [4]. Yet they frequently live inside an HVAC maintenance contract, fenced off from the Legionella regime that covers the hot and cold water.

The fix: confirm every tower is notified, written into the control scheme, and monitored to the frequency your risk assessment sets [2]. If you are not even certain whether the site has one, that uncertainty is itself the finding. Cooling towers and evaporative condensers goes into the controls in depth.

The one fix that does the most work

If you change only one thing, build a single ownership map of the water system. Every tank, riser, branch, outlet, mister, fountain and tower, each marked with two facts: who is responsible for it, and how often it is actually used. That one document quietly resolves four of the five mistakes above — it surfaces the unowned pipe, flags the void units, exposes the dead legs, and pulls the cooling tower back into view. It also gives a contractor, an incoming facilities manager, or an enforcing officer a single place to understand the building. Everything else — temperatures, flushing, sampling, recording — is easier to schedule and defend once you know what you are managing and who owns it. A digital logbook makes that map far easier to keep current across a churning estate; Case study: improved compliance with digital logbooks shows the difference that makes in practice.

How to use this

This is general guidance, not a control scheme for your building. The aerosol sources, temperatures, monitoring intervals and remedial actions that apply to a specific shop or centre come from a competent, site-specific risk assessment and the written scheme built from it — a single supermarket, a parade of unit shops, and a covered mall with a food court and rooftop plant are three different problems wearing the same label. Where this piece names a figure or a duty, confirm it against current HSE guidance and your own assessor before you act on it.

FAQ

Who is responsible for Legionella in a leased retail unit — the landlord or the tenant?

Usually both, for different parts. The landlord typically holds the duty for common parts (stored water, risers, plant and any cooling tower); the tenant for the water system inside their demised unit. The lease should define the boundary, and the duty holder for each part stays accountable even when the work is contracted out [1]. The practical risk is the stretch in between, so agree in writing who owns it.

Do small shops with only a toilet and a kitchen tap need a risk assessment?

Yes. The duty to assess and control the risk applies regardless of size, and a low-use outlet in a quiet shop can carry more risk than a busy one because the water sits still for longer [1]. The assessment may well be brief and conclude the risk is low — but that conclusion has to be reached and recorded, not assumed.

Are the produce misters in a supermarket a real Legionella concern?

They are worth assessing, because they deliberately create a fine spray that staff and customers breathe in. Whether they amount to a meaningful risk depends on how they are fed, stored and maintained, which is a question for your risk assessment [3]. The aim is not to panic about the veg counter but to make sure it was actually considered rather than waved through as harmless.

Sources

[1] HSE, “Legionnaires’ disease. The control of legionella bacteria in water systems - Approved Code of Practice and guidance (L8)”. https://www.hse.gov.uk/pubns/books/l8.htm [2] HSE, “Legionnaires’ disease: Technical guidance (HSG274)”. https://www.hse.gov.uk/pubns/books/hsg274.htm [3] HSE, “Systems most likely to create legionella risk”. https://www.hse.gov.uk/legionnaires/risk-systems.htm [4] HSE, “Other duties: RIDDOR and notification of cooling towers or evaporative condensers”. https://www.hse.gov.uk/legionnaires/what-you-must-do/duties.htm [5] CDC, “How Legionella Spreads”. https://www.cdc.gov/legionella/causes/index.html