Chislehurst Supply Pipe Leak Under the Drive

Very probably. A sudden jump in the water bill, a patch of lawn that stays soft, and nothing wrong inside the house is the classic sign of a leak on the underground supply pipe, and on a large Chislehurst plot that pipe can run forty metres under the drive and garden. Confirm it with a meter test, then have it located with acoustic equipment or tracer gas so the drive is opened in one place, not along its length. The pipe is yours, and Thames Water expects a leak on it fixed within four weeks.

Why big Chislehurst plots get this

Chislehurst, BR7, has some of the largest plots in the borough: big Victorian and Edwardian houses round the Common and on the Camden Park estate, and Arts and Crafts and inter-war houses set well back from the road. The supply pipe has to cross all of that ground between the outside stop tap at the boundary and the house, often under a gravel or block-paved drive, sometimes under lawns and planting.

Many of those pipes are original lead or galvanised iron, and the ground is clay. Clay shrinks in a dry summer and swells in a wet winter, and every cycle bends a long buried pipe. The longer the pipe, the more of it there is to crack. Because the water goes straight into the ground, you often see nothing at all. Thames Water says over 95% of leaks are never seen by customers.

How do I confirm it is the supply pipe?

The two-stage meter test:

1. Turn off every tap and appliance in the house, including any outside taps and garden irrigation, and make sure nothing is refilling.
2. Read the water meter, usually in a chamber near the boundary, and photograph it.
3. Wait 30 to 60 minutes without using water, and read it again.
4. If it has moved, turn off the internal stopcock clockwise and watch the meter for ten to fifteen minutes.
5. If the meter keeps moving with the stopcock off, the leak is on the underground pipe between meter and house.

If the meter stops when the stopcock is closed, the leak is inside, and on a big multi-bathroom house that could be a cistern passing water, a tank overflowing in the loft, or a pipe in a floor. Annexes, pool rooms and garden taps plumbed off the main supply can also hide leaks.

Who is responsible?

Thames Water supplies Chislehurst. It says it is responsible for public pipes under roads and pavements, and that you are responsible for leaks within your property boundary, including the supply pipe under your garden and driveway. Once you know about a leak on your side, Thames says you must fix it within four weeks. If you are on a meter and get it fixed in time, you may be able to claim a leak allowance for the water lost, and Thames notes it may inspect work not done by a WaterSafe approved plumber.

How is a leak found under a drive?

The tools, roughly in the order they are used:

• Acoustic listening. Pressurised water escaping from a pipe makes a noise. Listening sticks on the stopcock and outside tap, and a ground microphone moved along the line of the pipe, narrow down where it is loudest.
• Pipe location. Before you can listen along a pipe you have to know where it runs. On old properties nobody knows; a tracing tool can follow a metal pipe, and for plastic, a signal can be sent along it.
• Tracer gas. For quiet leaks, or plastic pipes, the pipe is drained and filled with a harmless hydrogen-nitrogen mix. The gas comes up through the ground or the joints in the drive at the leak, and a detector picks it up.
• Thermal imaging helps where the leak is close to the house or under a floor.

The result should be a mark on the drive, and one hole of a sensible size.

Repair or replace?

On a forty-metre run of ninety-year-old lead or iron, repairing one leak often just moves the problem to the next weak spot. It is frequently cheaper overall, and much less disruptive, to lay a new blue polyethylene pipe on a new route: along the edge of the drive, under a lawn instead of paving, or pulled through underground with a mole so only the ends are dug. A new stopcock inside the house comes with it.

We agree the price with you before any work starts. The things that drive it are the length of the run, what has to be lifted, and how the pipe comes into the house.

What about the drive itself?

Block paving can usually be lifted and relaid cleanly over the dig. Gravel is easy. Tarmac and imprinted concrete need patching, which is why locating the leak precisely matters, and why a new route that avoids the drive is often the better plan.

What if the leak is not underground?

If the stopcock test shows the leak is indoors, the big-house suspects are a toilet cistern passing water, a loft tank overflow, a failed valve on a cylinder, or a pipe under a floor. Thermal imaging and moisture mapping find those. Our guide to a leak on a long private supply pipe in Biggin Hill covers shared supplies and even longer runs. More about BR7 on our Chislehurst page.

Need a plumber now?

If your meter test points at the supply pipe, Call 07868 281022. Tell us your postcode, what the meter does with the stopcock on and off, and where you see any wet ground. We do leak detection in Chislehurst and water leak repairs across BR7.