Why Is My Water Bill So High? Hidden Leaks

How do I know if a hidden leak is causing my high water bill?

Do a simple meter test: turn off every tap and water-using appliance, note your meter reading, wait one to two hours with no water used, then read it again. If the numbers have moved, water is escaping somewhere in your system. A hidden leak rarely announces itself, so the meter is your most reliable early warning.

Watch for these common signs alongside the bill spike:

• The meter dial or digits keep moving when all taps are closed
• Damp patches, tide marks, or peeling paint on walls and ceilings
• A musty smell that will not clear with ventilation
• Warm patches on floors (a clue to hot-water pipe leaks)
• The sound of running or trickling water with nothing switched on
• Unexplained mould growth, especially in a corner or low on a wall
• Reduced water pressure at the taps

Where are hidden leaks most likely to be?

Most hidden leaks sit in the places you cannot easily see: underground supply pipes, pipework buried in walls or under solid floors, and concealed connections behind kitchen and bathroom units. Toilet cisterns are a frequent culprit because a worn flush valve can leak silently into the pan for months without a single visible drip.

Underground supply-pipe leaks between the boundary and your property are among the most expensive on a bill, as they run continuously and can wash water away before it ever reaches the house. Central-heating and hot-water circuits hidden beneath floors are equally common in older properties, where original pipework has never been replaced.

Can a water leak cause damp and mould?

Yes, and it is one of the most misdiagnosed causes of damp in London homes. A slow concealed leak keeps plaster, timber, and masonry permanently wet, which reads exactly like rising or penetrating damp to the untrained eye. People often treat the surface with paint or a dehumidifier while the real problem, escaping water, continues unchecked behind the wall.

Left alone, leak-driven moisture rots skirtings and joists, blows plaster, and feeds black mould that returns however often you wipe it away. This is where professional leak detection matters: pinpointing the source before you spend money on cosmetic repairs that will simply fail again.

What should I do first if I suspect a leak?

Confirm it with the meter test, then narrow it down before calling anyone out.

1. Read your meter, use no water for one to two hours, then read it again to confirm movement
2. Check every toilet cistern with the food-colouring test
3. Look under sinks, behind the washing machine, and around the boiler for damp or corrosion
4. Feel floors for warm or cold damp patches and inspect walls for tide marks
5. Contact your water supplier, who may investigate the external supply pipe up to the boundary
6. Arrange a professional survey if the source is inside and still hidden

Do not start ripping up floors on guesswork. A proper survey finds the source with minimal disruption and gives you evidence to act on.

What does a Damp, Mould and Water Damage Assessment include, and what does it cost?

We confirm the price on a written quote once we understand the problem. Our Damp, Mould and Water Damage Assessment (what many people call a damp survey) is designed to trace the leak and diagnose the resulting damp in one visit. You receive a full insurance-ready written report with a photographic evidence appendix, clear findings, and prioritised recommendations, so you know exactly what is wrong and what to tackle first.

The survey uses moisture readings and targeted inspection to separate a genuine leak from condensation or other damp causes, which is the difference between fixing the problem once and paying for repeated failed repairs. As for remedial work, the cost depends on the type of leak, its location, how much building fabric has been affected, and the access required to reach it. We set that out in words in your report rather than guessing at figures before the source is confirmed.

Arrange a leak and damp survey with Damp & Mould Solutions UK

Damp & Mould Solutions UK carries out Damp, Mould and Water Damage Assessments across the UK, including Central, North, South, East, and West London and the surrounding boroughs. If your water bill has jumped and you suspect a hidden leak, call us on 020 3051 8478 or send photos via WhatsApp for an initial view before we arrange your survey.

If you've got damp, mould, or a leak, you already know it needs sorting.

The longer it sits, the worse it gets. Get in touch and we will agree a date with you. If it is urgent, say so when you call.