Replacing corroded mains water copper pipe

22 Oct 2013
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United Kingdom
We are having a front extension built and the ground works team found the mains water pipe with their JCB whilst excavating the foundations.

The pipe is 1/2" copper, no protection around the pipe, just laid directly in the clay soil from the house to the supply stop cock just outside the house boundary.

No major damage to the water pipe, just a small hole which I repaired with a brass compression slip coupling.

I though this would be a quick repair, but have since found multiple pin holes along the length of the pipe, which weren't caused by the JCB.

I've now excavated around the copper water pipe by hand to where it enters the house and found that the clay drain pipe that has been used to duct the pipe under the floor slab was completely full of water, so I can only assume there are further pin hole leaks in the pipe under the house.

I can only assume the pipe has been leaking for years underground.

Only option now is to replace the whole length of pipe with MDPE pipe, as I don't want to build our extension over the existing copper pipe even if I can fix all the current leaks.

I can probably access the outlet of the mains supply connection without having to excavate outside our boundary, by excavating down and under the dwarf wall which is on the boundary.

Do I need to get permission from the water supply company to connect up the new pipe or do I have to get them to connect it up?

I will also have to route the new pipework inside the house differently, as the mains water supply current comes up through the floor in the far corner of our kitchen, which is a good 6m from where the pipe enters under the house.

Pulling up our new granite tiled floor in the kitchen is a last resort option, so I am going to look at ways of routing the new pipe behind the kitchen units, but I will still need to break out the concrete floor slab in the hall to intercept the clay drain pipe that's ducting the existing copper supply pipe.

Is this a common problem with using copper pipe for the underground water supply?
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Depending on the type of soil that it has been laid in then corrosion can occur. Clay tends to be more alkaline and as such will draw copper from the pipe. It shouldn't have been laid unprotected.
When installing your new pipe it needs to be laid between 750mm and 1350mm deep ideally bedded in sand.
Notification to your supplier that the work is being done is required and ensure that the person doing the work has his water regs ticket and is accredited with the supplier, this allows them to issue a completion certificate otherwise you need your supplier to visit and certify the work is satisfactory before it is connected to their mains and covered.
Thanks for the information.

The soil is heavy clay and the pipe has probably been underground for 30+ years.

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