Leak from internal stack

[ChrisR]

Internal plastic soil pipe is against party wall.
It has branches at floor level in basement, ground and second floors.
Neighbour has a damp patch, 200mm diameter at about 2m high, in basement.
House is large early Vic, or older.

I found an inspection hatch at basement, floor level which was cracked and leaking a few drops.
So either the water was leaking here and rising about 2 metres, or there's a leak above which just happens to go through at that height.

I've heard damp can only rise 1 metre, but I've witnessed it going higher than that, many times.

What do you think?

Nearly all the pipe is boxed in. Any cunning methods of finding the leak if it's higher up? Lights and cameras?

Also posted in Building section.

 

[Space cat]

A leak big enough to make a damp patch on the other side of a wall would also send plenty of water down the outside of the pipe on your side of the wall. Is there anywhere you can check for this?

 

[chrishutt]

If early Victorian I presume the walls are stone construction with rubble infill, maybe 500mm thick. Strange things can happen with damp in such walls, with water travelling according to the porosity of particular stones. Damp from ground level can emerge in a patch even two metres up.

It may be that basement walls on one or both sides have previously been sealed or tanked even. This could result in water rising to a point above the sealed level. Also water penetrating from above could pass a long way down through the inner rubble core of the wall before finally emerging as a damp patch.

As for solving the problem, the only thing I can think of is to drill some exploratory holes into the wall in the vicinity of the damp patch. This should reveal the direction that the damp is coming from, once you start getting samples of the mortar / rubble fill coming out. It may be unrelated to the soil stack.

 

[Softus]

Since this is a basement, the solution to your problem might lie in the answer to the question "what keeps the dry parts dry"?

 

[ChrisR]

Well, either tanking(s) or a damp course.
If the former it's odd that the patch lines up exactly with the pipe.
If the second it's odd that it should rise 2 metres, and line up with the pipe.
or did you mean summat else?

 

[Softus]

I wasn't implying any hidden meaning, just that a basement is likely to be wet unless it's tanked.

If you bung the drain at a manhole (and the basement branch), then fill the soil pipe from the ground floor WC, does the water level stay up?