A leak in an office, shop or restaurant is handled differently from one in a house. More people are affected, the building usually has more than one occupier, the pipework is larger and less well documented, and the person who calls is often not the person who holds the keys, pays the bill or decides on the repair. Knowing what the job involves helps you get the right people and the right access in place early.
This guide walks through a commercial leak job from the first call to the final report. For an overview of the kinds of leaks commercial buildings suffer and why they matter, see our guide to commercial water leak detection.
What should happen first when a commercial property has a water leak?
- Make the area safe. Keep staff and customers away from wet floors and any water near electrical equipment, lighting or distribution boards. If electrics are affected, isolate them only where it is safe to do so, and involve an electrician.
- Find out who controls the water. In a multi-let building the main stopcock, risers and plant rooms are often in common parts controlled by the landlord or managing agent, not the tenant.
- Isolate as locally as possible. Close the nearest valve that stops the leak, rather than the whole building, if that can be done safely.
- Tell the landlord or managing agent. Most leases set out who must be notified and who arranges repairs. Early notice avoids arguments later.
- Protect stock, records and equipment. Move what can be moved and cover what cannot.
- Record everything. Photographs, times, meter readings and who was told. This helps the investigation and any insurance claim.
How is the water isolated without shutting the whole building?
A well-designed commercial building has valves on each floor, riser or zone, so a leak can be shut off without closing everything. In practice, several things get in the way:
- valves that are unlabelled, painted over or have not been turned for years and may not close fully;
- drawings that no longer match what is installed after years of fit-outs;
- tenants sharing a supply, so closing one valve affects a neighbouring business;
- heating, chilled water and domestic water on separate systems, each with its own valves and plant.
Part of the investigation is often simply establishing which valve controls what. That knowledge is worth recording for next time.
Why is a leak between units so hard to trace?
In a multi-storey or multi-let building, water rarely appears where it starts. It runs along concrete slabs, through ceiling voids, down service risers and along cable trays before it shows. The shop below may see the damage while the source is in an office above, in a common corridor, or in the unit next door.
That creates practical problems as well as technical ones:
- the engineer may need access to units occupied by other businesses;
- the landlord or managing agent may need to authorise work in common parts;
- each party may have a different insurer and a different view of where the water came from.
A clear, methodical investigation, with readings taken in every area the water could have come from, is what settles the question.
How does leak detection work in different commercial settings?
| Setting | Typical challenge | Usual approach |
|---|---|---|
| Offices | Suspended ceilings and raised floors hiding long pipe runs; water spreading across tiles | Moisture mapping above the ceiling, thermal imaging of pipe routes, pressure testing by floor or zone |
| Restaurants and commercial kitchens | Floors that are always wet from cleaning; heavy waste loads; grease in drainage | Separating supply and waste with meter and isolation tests, then flow or dye tests on the waste |
| Shops | Fixed displays and stock covering walls and floors; limited time before opening | Non-invasive methods first, with any opening agreed in advance |
| Plant rooms | Several systems side by side; noise from pumps and plant | Testing each circuit separately, with plant switched off where possible for acoustic work |
| Risers and common parts | Shared pipework serving several occupiers | Coordinated access through the managing agent, with readings on each floor |
The methods are the same ones used in homes, including thermal imaging, acoustic listening, tracer gas and pressure testing. What changes is the scale, the coordination and the need to keep a business running.
Can the work be done out of hours?
Often, yes, by arrangement. Working after closing time or at weekends avoids disrupting staff and customers, and a quiet building with no water in use makes acoustic listening and meter tests easier to read.
Out-of-hours work needs some planning on your side:
- who will let the engineer in, and who holds alarm codes and keys to plant rooms and risers;
- whether building security needs names in advance;
- whether the facilities manager needs a risk assessment and method statement before work starts;
- whether neighbouring occupiers need to be told if their supply may be isolated.
Our commercial leak detection is priced from £300. Emergency attendance is from £300 in working hours and £450 out of hours, and we confirm the price before anyone is sent.
What happens during the repair itself?
Once the leak is located, the repair is carried out by a plumber or the building's maintenance contractor. On commercial jobs there are a few extra points to cover:
- Agree the opening before it is made. Ceiling tiles, raised floor panels and plasterboard are cheap to open. Tiled floors, stone and fitted joinery are not.
- Re-test after the repair. A pressure test or meter test on the repaired section shows the leak has actually stopped before the area is closed up.
- Think about water hygiene. HSE guidance on managing legionella in hot and cold water systems advises removing dead legs and dead ends in pipework. A repair that leaves a capped-off length of redundant pipe should be flagged to whoever manages the building's water risk assessment.
- Let things dry. Wet screed, plasterboard and ceiling voids need drying and checking before finishes go back. Our guide to water damage restoration after a leak covers this stage.
What does the facilities manager or landlord receive afterwards?
For a commercial job, the written report is often as important as the fix. It is what the landlord, the tenant, the managing agent and the insurers all work from. A useful report sets out:
- the property, the areas inspected and who gave access;
- the methods used and the readings taken;
- where the leak was found, with photographs and marked-up locations;
- the likely cause, where it can be established;
- the extent of the damp found, and any areas that could not be inspected;
- recommended next steps.
Who pays for what is decided by the lease and the insurance policies, not by the leak detection engineer. The report gives the parties the facts to work it out. Our guide to what a leak detection report should contain goes into more detail.
What cannot be promised on a commercial leak job?
It is better to know the limits at the start:
- intermittent leaks, such as those that only appear under heavy use, may need more than one visit to catch;
- if access to a neighbouring unit or a plant room is refused, the investigation can only report on what was accessible;
- leaks that are not from pipework at all, such as roof or façade water, need a different kind of investigation;
- seized valves or missing drawings can slow isolation down.
A good engineer tells you which of these apply as soon as they become clear, rather than at the end.
When should you call a leak detection specialist?
- water is appearing in your premises and the source is not visible;
- the damage is in one unit but the source may be in another or in common parts;
- water bills or plant pressures suggest a loss that nobody can find;
- a landlord, tenant or insurer needs an independent written account;
- the work has to happen outside trading hours.
See our commercial leak detection page, or call 020 3912 0200 to arrange access.
Frequently asked questions
Who is responsible for a water leak in a commercial property?
It depends on the lease and where the leak is. Tenants are often responsible for pipework within their demise and landlords for common parts and shared services, but leases vary. A clear report on where the leak is helps the parties apply the lease correctly.
Can a commercial leak be found without closing the business?
Often, yes. Most detection methods are non-invasive, and surveys can be arranged before opening, after closing or at weekends. Some tests need the water isolated for a period, which is easier to schedule outside trading hours.
How much does commercial leak detection cost?
Our commercial leak detection starts from £300. The final price depends on the size of the building, the number of systems to test and the access involved. Emergency attendance is from £300 in working hours and £450 out of hours.
Do you need access to neighbouring units?
Sometimes. Water often travels between units, so the source can be in the unit above, beside or in common parts. The landlord or managing agent usually arranges that access.
What should a commercial leak report include?
The areas inspected, the methods and readings, the leak location with photographs, the likely cause, the extent of damp, any areas that could not be inspected and recommended next steps.
