Anyone know about the merits of replacing an old, lead, water supply pipe?

[Tatlerer]

Hello
We have a leak in our main water supply pipe, found by builders who are pulling up the floor and digging trenches in prep for a new extension. The leak is in a breaker(?) where the main pipe forks off into two places- the outside water tap and the main house stopcock.
Water company came out today and as we have insurance said they would repair the leak at the break. There are no other leaks running from the water supply at the property boundary up to the point of that breaker.
However, as it's an old lead pipe, I'm minded to get the whole thing replaced with a new plastic supply pipe which would have the added benefit of being able to run the supply direct from the pavement into what will be our new utility. Apparently these days it can be run in with a 'mole' rather than tearing up the existing driveway to the front of the property. I've heard it will also improve our water pressure.
I've got no idea how much this sort of thing costs- google ranges from £500-£1,500. Do you think it'd be worth it? Has anyone done similar and what did it cost you?
Thanks!

We did exactly this before starting the extension and loft conversion and whilst it was depressing to spend that sort of money on something so boring, it was totally worth it. Water pressure increased dramatically, stop cock is now easily accessible, and we were putting in a new boiler so all in, it meant that the water supply and pressure matched up to the increased size of the house. Think we paid about £1,000.

WRT lead in water... It's very low risk if you have quite hard water; the lead can't leach into the chemical spaces already occupied by Calcium ions.

It's very worthwhile to replace the lead pipe if you have soft/very soft water, then the lead will be leaching easily into your tap water.

Thanks Leggy, we're also putting in a new boiler- sounds like it's a good idea then! Really appreciate your advice, thanks

Good point ragged, hadn't even thought of that. It's pretty soft here I think (West Midlands).

Apart from potentially more leaks, old lead pipe is often squashed, which reduces the flow of water through it. Probably it will be half-inch internal bore, might even be 3/8"

If you run a new plastic pipe, it can be substantially greater bore (typically 25mm though 32mm costs little extra and is the same amount of work) which will greatly improve the flow. I guarantee you will be amazed and delighted.

It does not need to follow the same route as the old one. It must be deep enough to pass the water co inspection. Run it all the way from the meter or stopcock under the pavement to the internal stopcock (or beyond) and take a 22mm copper internal pipe for the hot water, and another for the cold, before reducing the pipe size. Have a full bore stopcock (don't allow the plumbers to use a smaller one, which will constrict the flow but will be cheaper for them). Find out the cost of digging a trench before you decide on moling. Plumbers are weedy fellows with delicate little hands but builders can use a spade.

This will enable you to get stupendous showers and bath-filling if you get an unvented cylinder, and, if you have a combi boiler, will be less prone to sudden changes in pressure and temperature when other taps or appliances go on and off.

Replacing the lead may also reduce lead content in the drinking water, especially if you are in a soft water area.

Look up your local water co's policy on lead replacement. There might be a subsidy or they might dig up the pavement free or at a reduced rate. You will need a sample of drinking water tested BEFORE YOU START WORK so request this at once as they may be slow to make an appointment. As you may know, lead is damaging to the brain and nervous system, especially in babies and children.

Changing the pipe does not alter pressure, so will not stress your taps or appliances. Pressure is not the same as flow.

...too slow

PigletJohn I was hoping you would reply, you are a hero!
This is the blurb on the Severn Trent website re lead replacements:
We offer a free replacement water connection if you live in an existing domestic property which has a water service pipe that is lead or you’re on a shared supply with a neighbouring property. The replacement connection we make will be 25 mm diameter and will be connected to the same water main as the existing supply. You will need to lay a new 25 mm service pipe out to the highway boundary.

So I take it that laying the pipe itself would be at our cost?

What would be the value in testing the drinking water (other than scaring myself half to death about all the leaded water we have been ingesting so far).

Stupendous showers unless, like us, you're up a hill and reliant on a dodgy pumping station thst craps out any time there's a power cut a in the general area to maintain any semblance of useful water pressure.

the value in testing the drinking water might be that it defines if you are eligible for subsidy. In some places if the reading is low they don't help. But from your quote it sounds like it applies anyway if you have lead pipe.

in your position I think I would run a 32mm pipe out to a pit just inside your boundary, where I would put a stopcock and a short length of 25mm for them to connect to the meter. The meter probably has 25mm connections. Have your pit brick-lined or a sectional concrete hole with an iron lid to prevent it collapsing from traffic. (this is normally done after the plumbing connection is finished). It needs to be roomy enough for you to get your arm down.

you can include a tee for a garden tap if you want.

Wanted to post to thank pigletjohn and others for your good advice. We had the old lead supply pipe replaced with a 32mm one on Friday. I will feedback at a later date- one the house is finished- on the water flow but at least we have no more leaks and no lead in the water!