How to repair oversite after new water main?

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Merged to other thread. Please do not duplicate your posts.
Another question:

If they mole in this MDPE pipe and come up through the oversite beneath the suspended timber floor - will this disturb any DPM in the oversite and how can it best be repaired?

View media item 106995
Cheers
 
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Hi

I'm considering getting a lead water main replaced with MDPE pipe.

The existing pipe enters the property directly underneath the suspended timber floor in the hallway. The property was build in 1934.

Here is a picture:

View media item 106995
I'm getting quotes for thrust moling a replacement.

If the replacement pipe enters in a similar manner, will it disturb any DPM present in the oversite and is there any way that this can be repaired?

Cheers
 
Unlikely to be one, and it won’t be hard to make good around the new ducted pipe. You could put a bit of liquid dpm around it if you’re concerned
 
A 1930s house probably has a rather weak and crumbly oversite, with no DPM. Polythene sheet had not been invented. I bet if you scrape it with a teaspoon you can make a groove.

A new plastic pipe does not have to follow the same route as the old one

I would insulate new plastic and lay it under the floor, drilling or chiselling diagonally down through the concrete and wall to meet the trench you dig in your front garden. Unless it is paved or concreted, this will not be a complicated job in warm dry weather.

When I did one of these I'm pretty sure Thames said it had to be 750mm deep, and they sent someone out to inspect it before I filled in the trench. Mine went over the top of a drainage pipe but he did not grumble about that.

Get as close as you can to the boundary and see what you can reach. I have heard of people scraping out the ground under the pavement to connect it themselves. In my case I had a services pit just inside the boundary, with an old stopcock, and I connected to that. There was a short stub of half-inch pipe but the flow through my new plastic was greatly improved, as @oldbutnotdead says

had I been less frugal I would have paid TW to make the connection to the meter. If I was getting an unvented cylinder I probably would have done. With the pit just inside the boundary It would not be difficult to do it at a later date, without needing a new trench.

I strongly recommend running it at full size inside the house, all the way to your full-size kitchen stopcock, then teeing off a pipe for the hot (to your boiler, tank or cylinder) and another for your cold taps. This will minimise the risk of uncomfortable showers.
 
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Like 23vc Doubtful a pre war house has a dpm under the oversite, cant see any in the pic.
For a lot cheaper than moling you could trench your new mains through the garden without disturbing any driveway blockworrk.
 

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