Plastic Pipe Drainage Leak

[keithw]

During renovation of old house in Spain new grey plastic drains were installed. I now have a leak. A central downpipe takes smaller pipes running from three bathrooms. All pipes are located inside a vertical cavity hacked into a 2ft thick wall, which was then bricked/plastered over. These bricks are the light Spanish type so can be hacked away for access. A previous leak was dealt with by builder (no longer my friend!) who opened the cavity and smeared grey glue/ sealant over offendng joints (same colour as pipe - see picture - any ideas what that was?). I plan to open up the cavity to locate the new (or old?) leak. Dismantling and redoing joints is really out of the question as cannot shift pipes without hacking away all wall, bathroom tiles etc etc. So need to find a way to plug the leaks at the joints. Is there a technique anyone can recommend? Special tape or sealant? I guess anything that sets hard will just crack?

[htg engineer]

Anything like paste or sealant is only ever going to be a temporary solution, the leak may keep occurring if there's any movement in the pipes etc.

You can try using solvent weld - or a leak sealant spray, but as you have said - this has already been tried once with no success.

You'd be better of getting new fittings and re-jointing - possibly even solvent weld for a stronger long lasting joint - rather than pushfit.

You wouldn't have to renew all the pipes, just the 3 socket soil boss pipe, and a cutting of each smaller pipe. Would that be possible ?

[keithw]

I really think cutting out and replacing is a last resort. Imagine a soil pipe that runs down two stories bricked up behind a wall - not sure theres much movement to pull/push joints together. The side pipes might be more flexible. Wish I could post picture I have to show you....
I really need some kind of patch-up solution before I get someone to come in and demolish walls etc. One thought I have is that the leak may be in a new place and that the previous repair has in fact held.... there are a lot of pipes. That downpipe has three bathrooms above it all with loo, sink and bath/shower. If I find that is the case then I still need to know what kind of goo or tape or whatever I need to patch the new leak up. Searching on internet it seems crucial to know whether the pipe is poly this or that or ABS or whatever. Is there any way of figuring out what kind of plastic it is and hence what goo to use? Any ideas?

[keithw]

manged to put up a pic of what it looked like last time it leaked - and the goo that the builder put on some of the joints. Any ideas?
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