How to Tell If You Have a Hidden Water Leak

Common signs of a hidden leak

A hidden water leak rarely starts as a dramatic flood. In London flats and older houses, it often shows up as a small damp patch, a stain on a ceiling, a swollen floorboard or a musty smell that will not clear.

• Damp marks that grow after showers, heating use or overnight.
• Paint bubbling, plaster softening or skirting boards swelling.
• A water meter moving when taps and appliances are off.
• Boiler pressure dropping repeatedly after being topped up.
• Water stains below a bathroom, kitchen, airing cupboard or boxed-in pipe run.

Why the leak is not always above the stain

Water follows joists, pipe routes, boxing and light fittings before it becomes visible. A ceiling stain in one room can be caused by a bathroom fitting, central heating pipe, waste pipe or shared riser several metres away.

What to check before calling

If it is safe, check whether the leak changes when the shower, bath, heating or kitchen appliances are used. Look at the boiler pressure gauge, stopcock location and any visible pipework. These details help the engineer attend with a better idea of the fault.

When to call urgently

Call quickly if water is near electrics, the ceiling is sagging, a neighbour below is affected, or the leak is spreading. For hidden leaks in flats, it is also worth speaking to the building manager or landlord if shared pipework may be involved.

Emergency Plumbing London provides leak detection in London for hidden leaks, ceiling leaks, burst pipes and central heating leaks across West and North London.