Water meter moving in your new build? How to check for a hidden leak

Before you start: find the meter and the stopcock

On a new estate the meter usually sits in a small chamber with a round or square cover at the edge of the property, in the pavement, the driveway or the front garden. Almost every home built in England and Wales since 1990 has a meter. If you cannot find yours, ask the builder or your water company where it is. The internal stopcock is normally under the kitchen sink, and sometimes in a utility room or the garage.

Photograph the meter reading the day you move in. It gives you something to compare against later, and it is the first thing anyone will ask for.

Step 1: read the meter with everything off

Turn off every tap, the dishwasher, the washing machine, any water softener and the outside tap, and wait until no toilet is refilling. Read the meter, including the small digits or red dials, then read it again thirty minutes later. Many meters also have a small star or disc that spins with any flow at all.

If your water company has fitted a smart meter, its app or online account may show use through the night. A line that never drops to zero at three in the morning tells you the same thing as a spinning dial.

Step 2: close the stopcock and read it again

Close the internal stopcock fully and watch the meter for ten minutes.

Step 3: the usual culprits inside a new house

Small faults account for plenty of creeping meters, and in a new house they are easy to miss because nothing looks old enough to go wrong.

• Toilets. The valve in a push-button cistern can let water trickle into the pan all day. Look for a thin, steady ripple running down the back of the bowl.
• Appliances and softeners. A washing machine or dishwasher hose that was never fully tightened, or a water softener stuck in its cleaning cycle.
• The outside tap. A drip at the back wall, or a split hose connector left on it.
• Pipes behind new plasterboard. A damp patch, a stain in the ceiling below a bathroom, or a bulge in the plaster where something was fixed to the wall.
• The heating. The heating system is sealed, so a leak there usually shows as a boiler losing pressure rather than a moving meter. If the boiler keeps needing topping up, mention that too.

Isolate each suspect in turn and watch the meter. When it slows, you have found one of them; when it stops, you have found the last.

Step 4: if the meter turns with the stopcock closed

The supply pipe is leaking somewhere between the meter and the house. On a new build that usually means under the driveway, a path or the garden. Look for block paving that has sunk, a patch of lawn that stays wet in dry weather, or water sitting around the meter cover. Ofwat's guidance is that the supply pipe, from the property boundary or the water company's stop tap up to the first stop tap inside, is usually the owner's responsibility. In the first two years the builder may have to put right a defect in how it was laid, so tell them as well. On some estates one supply pipe feeds several homes, which your deeds or water company can confirm. Finding it takes acoustic listening and tracer gas, then one small dig once the spot is known. How ADI investigates new build supply pipes.

Ring your water company before you pay for anything

Ofwat says most water companies will find and repair a first leak on a supply pipe, and most will reduce the bill with a leakage allowance if the leak is found and repaired promptly. What they offer, and the proof of repair they ask for, varies from company to company, so ask them first. If they will not help, or the leak is inside the house, that is when a leak detection survey comes in.

Turning the meter reading into litres

Meters read in cubic metres, and one cubic metre is 1,000 litres. A leak of 10 litres an hour barely moves the dial in half an hour. Over a day it adds up to 240 litres, about three bathfuls, from a house where nobody has turned on a tap.