Lead Supply Pipe in a Sidcup House: Signs and Next Steps

Look at the pipe where it comes up out of the floor into your stopcock. If it is dull grey, soft enough to scratch to a silver shine, with no screw joints and fat rounded swellings where it joins, you have a lead supply pipe. Thames Water says you may have lead if your house was built before 1970 and has never been fully replumbed, which covers most of Sidcup’s 1930s semis. It is worth replacing on your terms, before the clay under the front path cracks it for you.

Why so many Sidcup houses still have one

Sidcup was largely built in the 1930s, and the supply pipe was run in lead or iron under the front path to the house. Since then, almost every Sidcup semi has had a new kitchen, a new bathroom (often two), central heating, and probably a new boiler. None of that work needs anyone to dig up the front path. So the one pipe in the house that has never been touched in ninety years is very often the one that brings the water in.

What are the signs of an old supply pipe?

At the stopcock

• Lead: dull grey, thick, soft. A coin scratch shows bright silver. Smooth curves rather than elbows, bulbous “wiped” joints, no threads. A magnet will not stick.
• Galvanised iron: grey or rusty, hard, threaded joints. A magnet sticks. Iron rusts from the inside, narrowing the bore.
• Blue or black plastic: already replaced.

Around the house

• Weak flow at the kitchen cold tap, especially when another tap is running. Old iron furs up inside; old lead can be squashed or kinked.
• A water bill that jumps with no change in how you use water, often in late summer or autumn.
• A strip of lawn or path that stays damp, or a soft spot in the front garden.
• A meter that creeps with every tap in the house turned off.

Why do these pipes fail in Sidcup?

The ground under Sidcup is clay. It shrinks in a long dry summer and swells again when the rain comes back, and every cycle bends whatever is buried in it. A lead pipe is soft and old; an iron pipe is thin and rusting. Either one eventually cracks or pulls at a joint. Because it is a metre down and leaking into clay, you usually see nothing. Thames Water notes that over 95% of leaks are never seen by customers because they are often deep underground.

Who owns which part of the pipe?

Thames Water supplies Sidcup, which is in the London Borough of Bexley. The communication pipe from the main in the road to roughly your boundary is Thames’s. The supply pipe from there to your house is yours, as is everything inside.

Thames runs a lead pipe replacement scheme. If you cannot replace your pipe yet, call Thames Water on 0800 316 9800 and ask about sampling. Thames says that if your water shows raised lead, it will only replace its own communication pipe. Ask Thames how its scheme works for your address, and whether it can renew its side when you renew yours, so you are not joining new plastic to old lead.

What does a replacement involve?

For a typical Sidcup front garden the work goes like this:

1. Confirm where the old pipe runs, from the outside stop tap to where it comes up inside.
2. Dig a narrow trench along the route, or use a mole to drive the new pipe underground with only a hole at each end.
3. Lay new blue polyethylene (MDPE) pipe at a frost-safe depth.
4. Bring it into the house through a sleeve in the wall or floor.
5. Fit a new stopcock that turns easily, with a drain-off valve just above it.
6. Connect to the house plumbing and pressure-test the new pipe.
7. Reinstate the path or lawn.

With a new pipe and a new stopcock, the flow at your taps usually improves noticeably, especially if the old pipe was iron.

We agree the price with you before any work starts. The things that change the size of the job are the length of the run, what is on top of it (lawn, block paving, a concrete drive), and how the pipe enters the house.

Is it worth doing if it is not leaking?

Thames publishes its own guidance on lead and drinking water, and that is the place to read about health. From a plumbing point of view, the case is simple. The pipe is ninety years old, it is in moving clay, and when it fails you will be digging the same trench anyway, but on a deadline. If you are on a meter, Thames expects a leak on your side to be fixed within four weeks of you knowing about it; do it in time and you may be able to claim a leak allowance.

If it is already leaking, find the leak first. Our leak detection in Sidcup page explains how the leak is pinned down without digging up the whole front garden.

What about hard water?

Sidcup’s water is very hard, around 331 mg/l in its Thames Water supply zone. A new supply pipe will not change that, but a new stopcock and a properly sized pipe at least give you a clean start. If you are thinking about a water softener, the time to plan the plumbing for it is when the new supply comes in, with a separate hard-water drinking tap in the kitchen as Thames recommends.

Our guide to lead pipes in Beckenham and Park Langley homes covers the same question in older Victorian and Edwardian houses, where the runs are longer and the pipe often enters through a cellar.

Need a plumber now?

If your old supply pipe has started leaking, or you want it checked and replaced, Call 07868 281022. Tell us your postcode, what you can see at the stopcock, and whether the water is off. We handle water leaks in Sidcup across DA14 and DA15. More about the area on our Sidcup page.