Internal connections?

[NSBC]

I need to connect to a damaged 100mm (internal size) plastic drain pipe which in embedded in hardened concrete under my garage. What makes it worst is the the end of the pipe in under a non supporting pillar and I don't wish to upset the foundations any more than I have already. Every time I chip at the surrounding hardened concrete around the pipe it is so hard the splinters damage the pipe.

I know it is not ideal but I am thinking of inserting another tube (with an external 100mm measurement and 3 mmm think) and gluing it in place and then glue another peice of the existing pipe with (internal size 100mm) to make the join.

I know a small amount of water will never naturally drain away, but at the decline is steep this should be minimal.

Sorry if I have gone on a bit, but any help would be very much appreciated.

[84-1093879891]

The correct way to do this is to use a small angle grinder or similar to cut away the concrete surround, a bit at a time, until there's sufficient room to accommodate a coupling.

Your plan is feasible, but somethijg I would only use if there was no other option and on a SW system. I'd be reluctant to use it on a FW system just in case the lip formed by the internal coupling piece was to snag something, and "Feminine Hygiene Products" are a particular nuisance in this regard.

If you could fashion the proposed internal coupling to eliminate the lip by chamfering the upstream edge, that would be advantageous, but I repeat that use of a proper external coupling is preferable.

[plumblocal harry]

We had a similar problem recently with a concreted over salt clay pipe. We used a 3 inch angle grinder, hammer and chisels and dressed the pipe to accept a Flex seal. We used the Flex seal because we could not create a perfectly circular finish on the concreted over pipe, and the Flex seal was able to accept the slightly oval shape we manufactured. It all worked well and sealed up beautifully. And by the way Tony we are "Plumbists" and we did it all in the rain.