Advice · Derby & Derbyshire
A leak under the floor is one of the more frustrating problems a homeowner can face, because you can often hear the boiler topping up or see the water bill climbing without any obvious wet patch to point at. The good news is that you can narrow it down a long way yourself before anyone lifts a single tile or floorboard. This guide walks through what to check, what the signs mean, and where the limits of DIY tracing really lie.
Before pulling up flooring, prove the water is going somewhere it should not. Turn off every tap and appliance, then watch your water meter for 30 minutes. In Derby most meters are in a small chamber near the front boundary under a plastic lid, and the small dial or red numbers will creep if water is passing through. If the meter is still, the problem is probably a drain, roof or condensation issue rather than a pressurised pipe.
Then isolate. Close the internal stop tap, usually under the kitchen sink, and check the meter again. If it stops moving, the leak is inside the house. If it keeps moving, the leak is on the supply pipe between the meter and the stop tap, which often runs under a hallway or front room floor in older Derby terraces and semis.
For heating leaks, the check is different. Note the pressure gauge on a combi boiler when cold. If it drops from around 1 to 1.5 bar to near zero over a day or two and there is no drip at any radiator valve, the loss is likely in pipework buried in a solid floor.
Solid concrete floors hide leaks well but not completely. Look for warm patches on a floor when the heating has been off for hours, tiles that have lifted or cracked along a line, laminate that has swelled at the joints, or a damp smell that seems to come from nowhere. Skirting boards with peeling paint or a tide mark along the bottom are a frequent giveaway, as water tracks sideways under the screed and wicks up the wall.
Suspended timber floors behave differently. Boards may feel springy or soft, and you might hear a hiss or trickle from an airbrick outside on a quiet evening. If you can lift a board or access a hatch, a torch and a mirror will often show water sitting on the oversite or dripping from a joint. Do not assume the wet spot is directly under the leak. On a concrete slab water can travel two or three metres before it surfaces.
Work out what runs where. Hot water pipes, heating flow and return, cold mains and sometimes the boiler condensate all cross under floors. Feel radiator pipes to see which room the heating drops leave the boiler towards, and note where the kitchen and bathroom sit relative to each other. Most leaks are at joints, bends or where a pipe passes through a wall, not in the middle of a straight run.
A cheap moisture meter, around 20 to 40 pounds, lets you map the damp area on a wall or floor rather than guessing. Mark the readings with masking tape and you will usually see a clear centre. If you have underfloor heating, get the manifold and pipe layout drawings if they exist, because pipe loops are close together and a random dig can cause a second leak.
Resist the temptation to start breaking out concrete on a hunch. A single wrong hole in a screed costs more to repair than a proper trace, and homeowners in Derbyshire often find the wet patch is the exit point, not the source.
Professional tracing uses tools that do not involve destructive work. Acoustic listening equipment picks up the sound of water escaping under pressure through a slab. Thermal imaging shows the heat signature of a hot water or heating pipe and the cooler spread of water around a break. Tracer gas, a safe hydrogen and nitrogen mix, is pushed through an isolated pipe and sniffed at the surface where it escapes. Together these normally pinpoint a leak to within a few centimetres, so the repair hole is small and in the right place.
Costs depend on the size of the house, how many systems need testing and how easy access is, but a full survey typically comes in at a few hundred pounds, and a written report is usually accepted by insurers for a trace and access claim. Check your buildings policy, because many cover the cost of finding the leak and making good, even if the pipe repair itself is not covered.
Call sooner rather than later if you have a boiler losing pressure daily, a supply pipe leak the water company has flagged, or any sign of water reaching electrics. Weeks of slow leaking under a floor can lead to sub floor timber rot or a heaving screed that costs far more than the trace.
Frequently Asked
You can confirm a leak exists and narrow it to a room using meter tests, boiler pressure and a moisture meter. Pinpointing the exact spot under a slab usually needs acoustic or thermal equipment, because water can surface some distance from the break.
Most UK buildings policies include trace and access cover, which pays for locating the leak and repairing the flooring afterwards. The damaged pipe itself is often excluded, so check your policy wording or ask your insurer before work starts.
A typical domestic survey in Derby takes two to four hours depending on the number of systems tested and how accessible the pipework is. You should be given the location and the cause on the day, with a report to follow.
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