Water Leak Under a Driveway or Garden? How We Find It

The supply pipe is the one pipe most people never think about. It leaves the boundary stop tap near the pavement, crosses the front garden or driveway and enters the house, often under the hall floor. When it fails, the water has nowhere to go but into the ground. Clay soil around Watford and much of north London holds that water. So the first sign is often a strip of grass greener than the rest, a bed that never dries out, or block paving that stays dark in dry weather.

Ownership matters because it decides who pays. The water company owns the main under the road and the communication pipe up to the boundary stop tap. Everything from that stop tap to the internal stopcock is the supply pipe, and it belongs to the property owner. Affinity Water serves Watford and most of Hertfordshire, Thames Water serves most of London, and both work on that same split. If water is rising near the pavement rather than on your side of the boundary, report it to the water company first. If it is on your side, the search and the repair are yours to arrange.

The survey starts at the meter with everything in the house turned off, then again with the internal stop tap closed. That proves the loss is on the supply pipe and measures it. We trace the pipe route across the drive or garden and listen along it with a Sewerin Aquaphon ground microphone. It hears water escaping under paving, concrete and soil. Plastic pipe carries very little sound. For that we drain the pipe, add a hydrogen and nitrogen tracer gas and follow it to where it surfaces. The leak is marked and photographed so one hand-dug hole reaches it, rather than a trench across the front of the house.

If you want the repair done on the same visit we can replace the failed section in MDPE or copper and reinstate the ground. Or we leave the hole marked for your own contractor. Hold on to the report and the repair invoice. Water companies may offer a leak allowance on the bill once a leak on your side has been found and fixed. The conditions vary, so ask them with the paperwork to hand. Tracer gas is a way of finding a leak and has nothing to do with gas safety. If you can smell gas at any time, leave the property and call the gas emergency number.