10 Signs You Have a Hidden Leak in Your UK Home (and What to Do)

The expensive plumbing leaks aren't the dramatic ones. It's the slow, invisible leaks — a pinhole in a hot-water feed running under floorboards, a weeping joint in a wall cavity, a degraded boiler condensate drain — that quietly do thousands of pounds of structural damage before anyone notices.

The Ten Warning Signs

If you spot any of these, investigate:

• 1. The water meter moves with everything off. Lift the cover (usually at your boundary), turn off every appliance, and watch. Any movement means a leak.
• 2. Unexplained jump in water bills. If consumption has spiked with no change in household use, something is leaking continuously.
• 3. Boiler pressure keeps dropping. A sealed heating system shouldn't need topping up. If you're filling it weekly, you have a leak in the heating circuit — often a pinhole under floorboards.
• 4. Damp patches that won't dry out. Especially low on walls, on ceilings under bathrooms, or on ground-floor walls below sinks.
• 5. Musty or earthy smells. The smell of damp behind plaster long before you can see staining.
• 6. Warm patches on floors or walls. A leak on a hot-water feed warms the surrounding fabric. Walk barefoot — you can often feel them.
• 7. Mould or mildew in unusual places. Behind kitchen units, in cupboards, around skirting — anywhere with persistent moisture.
• 8. Lifting tiles or peeling paintwork. Bathroom or kitchen tiles popping off the wall, or wallpaper bubbling, usually means moisture behind the surface.
• 9. The sound of running water with no taps on. Stand still in the quietest room of the house and listen. A faint hiss or trickle behind a wall is unmistakable once you've heard it.
• 10. Sudden drop in mains pressure. A large leak upstream of your stopcock can reduce flow at every outlet.

What a Leak-Detection Plumber Actually Does

• Acoustic listening: a sensitive microphone "hears" pressurised water escaping through the leak point. Works brilliantly on metal pipes, less well on plastic.
• Thermal imaging: an infrared camera shows temperature differences where a hot-water leak warms the surrounding floor or wall. Pinpoints leaks under screeded underfloor heating without lifting anything.
• Tracer gas: a hydrogen-nitrogen mix (safe, light, non-toxic) is injected into the depressurised pipe. It diffuses out at the leak point and is detected at the surface with a gas sniffer.

Combining the three techniques usually puts the leak inside a 10cm radius in under an hour — without smashing floors or walls speculatively.

What to Do Right Now If You Suspect a Leak

• Do the meter test — confirm a leak exists
• Check the boiler pressure gauge and note the trend
• Photograph any damp patches with date stamps for your insurer
• Check your home insurance for "trace and access" cover
• Call a leak-detection specialist — don't just call a general plumber

Pipe Assassin's leak detection service runs across London, Herts and Essex from our Enfield (EN2) base — see our London, Enfield, Hertfordshire and Essex pages.

Frequently Asked Questions