Lead Water Pipe Problems: Low Pressure, Leaks and the Thames Water Replacement Scheme

Do I have lead pipes? How to check in five minutes

Lead was banned in new water pipework in the 1970s. Thames Water says you are unlikely to have lead pipes if your home was built after 1970, or if all the pipework has been replaced since. Plenty of Victorian and Edwardian London terraces still have lead running from the pavement to the kitchen.

Look at the pipe where it comes up through the floor to your inside stopcock, usually under the kitchen sink, behind a kitchen unit or in the cupboard under the stairs. Then lift the cover of the outside stop valve and look at the pipe heading towards the house. The checks Thames Water gives are simple:

• Colour: unpainted lead is a dull grey, not the orange-brown of copper.
• Joints: lead joints are rounded and swollen, like a bulb or a cigar shape, where copper joints are small and neat.
• Scratch: a gentle scratch with a coin shows bright, silvery metal underneath.
• Tap: knock it with a metal object. Lead gives a dull thud; copper and iron ring.

A short length of copper at the stopcock does not prove the whole run is copper. Many lead supplies were joined to copper just below the floor, so check the pipe outside too.

What goes wrong with a lead supply pipe

Most calls about lead pipes are not about water quality at all. They start with a fault, and the lead pipe turns out to be behind it.

• Weak flow and low pressure. Old lead supplies are narrow, typically 12 to 15mm, where the modern standard is 25mm. A long, narrow run limits how much water can reach the house, which shows up when two taps run together or a combi boiler struggles to give a decent shower. See how to increase water pressure for the checks worth doing first.
• Weeping joints. The swollen wiped joints and the adaptor where lead meets copper are the usual weak points. They tend to seep rather than burst, leaving a damp floor void or a stain under the sink that never quite dries.
• A stopcock that will not turn. The brass stopcock on a lead supply may not have moved in decades. Forcing it can twist the soft lead pipe below and start a leak you cannot stop. Stopcock won’t turn covers what to try and when to stop.
• Hidden leaks underground. Lead is soft, so it can be crushed, split by frost where it runs shallow, or pulled apart when the ground moves. A meter that keeps running with every tap off is the usual clue.

What is safe to do right now

If a lead joint or the stopcock is leaking, turn the water off at the inside stopcock with steady hand pressure, clockwise. If it is stiff, do not use a long spanner or hit it. Go to the outside stop valve instead, remembering that on a shared supply you will cut off the neighbours too. Finding the external stopcock walks through that.

Do not cut, bend or clamp the lead pipe yourself. Lead is easy to damage and hard to rejoin without the right adaptor, and older homes sometimes used the metal water pipe as the electrical earth. Thames Water tells anyone replacing a lead supply to check their earthing, with their electricity supplier or a qualified electrician, for exactly this reason.

For drinking water, Thames Water’s advice while lead is still in place is:

• Run the cold kitchen tap for about two minutes first thing in the morning, or after you have been away for a few days.
• Flushing the toilet also helps clear water that has stood in the pipes overnight.
• Only use the cold kitchen tap for drinks and cooking. Boiling does not remove lead.
• If you use a filter, follow the maker’s instructions.

The Drinking Water Inspectorate says infants, unborn babies and children are most at risk from lead, because it can affect mental development. If you are pregnant or have young children and suspect lead pipes, ask Thames Water to test the water at your kitchen tap.

How the Thames Water lead pipe replacement scheme works

The scheme splits the pipe in two. Thames Water owns the communication pipe, which runs from its main in the street to the outside stop valve, usually at your boundary. You own the supply pipe from that valve to your inside stopcock, plus all the pipework inside. The who owns the water pipe guide explains the split in more detail.

If you are replacing your lead supply pipe, Thames Water will replace its lead communication pipe as well, provided you qualify. Its current criteria include that you:

• Have a property built before 1970 and suspect a lead supply pipe.
• Are not aware of Thames Water having already replaced its communication pipe.
• Have found your outside stop valve and confirmed whether your supply is separate or shared.
• Will bring the new pipe to the current outside stop valve, in line with it.
• Plan to replace your supply pipe within three months. After that you need a new application.
• Have decided whether to use an approved plumber or an independent one.

Step by step: from application to the new pipe in the street

You apply through the online form on the Thames Water lead pipe replacement page, and Thames Water’s guidance sets out the water regulations your new pipe must meet. Your plumber then replaces your side. What happens next depends on who you used:

• Approved plumber (Thames Water means one registered with WaterSafe): they issue a certificate for the work, you email a copy to Thames Water, and no open-trench inspection is needed.
• Independent plumber: Thames Water must inspect the new pipe in the open trench before it is buried. You call 0800 316 9800 to arrange it once the pipe is laid.

Shared supply? The shared length is the joint responsibility of you and your neighbours, and any branch that feeds only your home is yours alone. The scheme does not separate shared supplies. To discuss moving to a single supply, call Thames Water on 0800 009 3921, or get a quote for a new water connection.

What your plumber has to do to pass

Thames Water’s reconnection survey checks the new supply pipe against a set list. Your plumber should work to it from the start, because a failed survey means you do not qualify until it is put right:

• A 25mm pipe, or a like-for-like size if the old lead was bigger.
• A trench between 750mm and 1,350mm deep, with the pipe bedded in soft material.
• An approved inside stopcock, and an approved drain valve fitted upstream of it.
• The pipe insulated and ducted where it enters the building, and still laid at least 750mm down.
• The pipe laid in line with the outside stop valve, and tunnelled under any brick wall or fence on the way.

What replacing a lead supply pipe costs

Your side of the pipe is your bill, so this is the figure to plan for. The ranges below are typical UK market prices from published cost guides, not our prices. The guides say London and the South East pay towards the top, and they differ on the detail, so treat them as a budget rather than a quote.

• Per metre: guides put a new supply pipe at roughly £100 to £200 a metre whether it goes in by open trench or by moling, and disagree on which method is cheaper. Across a lawn a trench is simple. Under paving, a mole fired between two small pits avoids lifting the surface.
• A short run of about 5 metres, such as a small front garden to the stopcock: roughly £400 to £1,000.
• A straight run of about 10 metres from the boundary into the kitchen, across soft ground: roughly £900 to £1,800.
• The same run under a driveway, patio or public footpath: roughly £1,800 to £3,500.
• A long run of about 20 metres: roughly £2,000 to £4,000.
• Reinstatement: lifting and relaying block paving is quoted at about £30 to £60 per square metre. Drilling or thrust-boring under a drive instead of digging it up adds roughly £500 to £1,500, which is worth comparing with the cost of breaking out and relaying concrete.

Thames Water pays for its own lead communication pipe once you qualify, and its scheme page lists no charge for that part. The page, as published in September 2026, offers no contribution, grant or free work on your supply pipe or internal pipework, so you pay your own plumber for those. Some cost guides mention customer-side subsidies; they are not on Thames Water’s current page, so do not count on one, and ask when you apply.

What happens after you qualify

Once the certificate is accepted or the survey is passed, a Thames Water engineer traces its communication pipe, marks the road and pavement, and raises the job to replace it with a new 25mm plastic pipe. Permits and traffic management come first, so the date depends on your street. Thames Water aims to finish within three months of you qualifying, and the road is usually reinstated within two working days of the replacement.

You can backfill your own trench once your side has passed. Until the street side is done, keep flushing the cold kitchen tap for about two minutes before use. On the first day after the whole replacement is complete, Thames Water says to run every tap used for drinking or cooking for 10 minutes.

A 25mm supply in place of a long, narrow lead one often improves flow noticeably, especially when two outlets run at once. If pressure is still poor afterwards, the restriction is elsewhere, and low water pressure repair is the next step.