Repairing underground plastic soil pipe.

[Richard C]

The ensuite shower room in our bungalow has been plagued by a bad smell in for over 2 years since we moved in. Having checked out all accessible toilets & drains for problems, I suspected a leak under the shower tray. In reediness for a refit, I gutted the ensuite & dug out the shower tray & no surprise to find my theory correct. The takeaway pipe connection from the tray waste was very loose & the weak concrete under tray bedding was saturated. The waste & 40mm take away pipe is being replaced so that should not be a problem but I decided to explore further down t see if all was OK. On exposing the top of the 110mm soil pipe bend, I found the drain connector in a very bad state so this will also be replaced with a McAlpine 40mm drain connector but, to my horror, I found the top 50mm of the soil bend is also cracked in 3 places. Digging the whole lot up & replacing the bend & straight section to the manhole is not something I like to contemplate, both for the amount of work, cost & my advancing years means I'm no longer really up to this level of manual labour. Looking to repair, I tried painting over the cracks with plastic solvent adhesive but this didn't work as it's obviously the wrong type of plastic! Now thinking of trying a repair using fibre glass matting & resin but, not having any previous experience, my question is will this work? Will the glass resin adhere to the plastic drain pipe or will it just fall off as with the solvent adhesive? Or if anyone can suggest a successful repair method to save me digging up the ensuite floor & outside patio area to replace the bend & pipework I would be grateful.

 

[jj4091]

Is it possible to extend the waste pipe from the shower further into the soil pipe so that it is past the cracked section.

 

[Richard C]

Yes & I am also going to do that using an extra bend & a straight section of solvent weld pipe below the connector so the water will discharge 300mm or so down inside the straight section of soil pipe. I still want to make a repair to the cracks in the top of the bend if I can in order to fully restore the integrity of the bend. In theory, the bend should never see any water in normal shower use but you never know with communal drains & we have had I couple of blockages further down the line causing water to back up through the manholes!

 

[Alec_t]

Now thinking of trying a repair using fibre glass matting & resin but, not having any previous experience, my question is will this work? Will the glass resin adhere to the plastic drain pipe or will it just fall off as with the solvent adhesive?

If the fibre glass bandage goes right round the pipe it can't fall off. If the pipe surface is clean and dry (that might be difficult) the resin should bond to it (check the instructions re suitable materials).

 

[Richard C]

The repair can only be made inside the top of the bend, the outside & the rest of the bend is still buried in concrete floor 400mm below the floor. It will be fairly easy to clean & rough up the inside surface of the plastic but I'm unsure if the glass resin will successfully bond.

 

[jj4091]

I would think any epoxy putty would solve your problem, you can shape it however you would like it and it sticks to anything (especially your skin so use gloves if you decide to try it) https://www.google.com/search?q=plastic+metal+putty&sca_esv=74c6de03b5b81e4a&source=hp&ei=mJdMZ5aRG9OGhbIPnvnnIA&iflsig=AL9hbdgAAAAAZ0ylqD8s26QGwH-xhHtGPuZMzOEs3QLs&oq=PLASTIC+META;&gs_lp=Egdnd3Mtd2l6Ig1QTEFTVElDIE1FVEE7KgIIBTIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeSKl4UABYyDFwAHgAkAEAmAFroAGwB6oBBDEyLjG4AQHIAQD4AQGYAg2gAsQIwgILEC4YgAQYsQMYgwHCAhEQLhiABBixAxjRAxiDARjHAcICCxAAGIAEGLEDGIMBwgIOEC4YgAQYsQMY0QMYxwHCAgsQLhiABBjRAxjHAcICCBAAGIAEGLEDwgIOEAAYgAQYsQMYgwEYigXCAgsQABiABBiSAxiKBcICCBAAGIAEGMkDwgIFEAAYgATCAggQLhiABBixA5gDAJIHBDExLjKgB-pZ&sclient=gws-wiz hardens quickly also.

 

[Richard C]

So do you think an epoxy resin would be more suitable?

 

[Harry Bloomfield]

So do you think an epoxy resin would be more suitable?

I would suggest putty, if there are holes to fill, but resin to stick cracks together, and to spread beyond the cracks, for extra reinforcement. An alternative method you might be able to use, in combination with the resin, is plastic welding.....

Thin copper wire, formed into small zig-zag shapes, then pressed into the surface of the plastic, across the cracks, with a hot soldering iron,

 

[Hugh Jaleak]

Picture of damaged section might help advise what could be done.

 

[Richard C]

So what I've done is: rough up the whole area with 60 grit paper, cover the cracks with plasterboard tape (for the uninitiated, this is a very thin glass fibre mesh tape) and cover this with a good dose of Epoxy Resin. After setting, I applied another layer of plasterboard tape followed by another layer of Epoxy Resin. It's all set really well & seems strong so (hopefully) this will maintain the integrity of the pipe if the water backs up due to blockage down the line. My thanks to all who showed an interest.