How to repair rusted sewer vent pipe

[Smithrj]

Hi, the bottom 150mm or so of the sewer vent pipe outside our home has rusted away. I've cut away most of the rotten pipe but now need to figure out how effectively to bridge the resulting gap. There is a small collar of 100mm PVC inside the old connection on the ground, and the metal pipe itself is also 100mm diameter, so ideally I need something (preferably flexible) that will fit inside the ground connection and outside the metal pipe. Can anyone suggest a way of repairing or is this a job for a plumber? Many thanks.

[MitchellMc]

Hi @Smithrj,

It is a job that you could do yourself, but a bit of trial and error might be involved. 

The easiest option might be to glue a male to female connector similar to Holman 100mm 5° Male And Female PVC DWV Plain Bend into that 100mm pipe in the ground. Unfortunately, there is no straight-through connector in male to female. The straight connector is female and can't slip over the pipe in-ground. You could be really tricky and cut the male side off the five-degree connector. Once it's glued inside the 100mm PVC, you'll be able to slip the new piece of pipe over it.

Once you have the female connection installed, you can connect a Holman 100mm x 1m PVC DWV Pipe section to it. That section of pipe will be connected to the metal pipe with a Deks 100mm PVC To PVC Rubber Joiner. Hopefully, the flex of the rubber joiner makes up for the five-degree bend.

That all sounds a bit convoluted because you are trying to join off the inside of a 100mm pipe, whereas most fittings are for the outside.

What probably should be done here is that you remove the section of 100mm pipe and mortar from the terracotta pipe. A new section of Holman 100mm x 1m PVC DWV Pipe is joined to the metal pipe with a Deks 100mm PVC To PVC Rubber Joiner. The new section of 100mm PVC pipe is then cemented back into the terracotta pipe.

Please let me know if you have any questions.

Mitchell

[Smithrj]

Hi Mitchell,

Thanks so much for the information and product suggestions. I like the simplicity of joining a new piece of 100mm PVC pipe to the metal pipe with the Deks rubber joiner, I'll just need to get the old piece of PVC out and remove some of the mortar surround. Sounds easy enough (but probably won't be 😁). 

Rod.

[EricL · Accepted solution]

Hi @Smithrj 

It's great that you've received fantastic advice from my colleague @MitchellMc. Just to add to the suggestions, I recommend measuring the opening size of the pipe on the cemented portion. If the diameter of the pipe is standard 100mm, you can use a Holman 100mm PVC DWV Slab Adaptor to go directly inside that pipe. This adapter is built to repair just these kinds of situations or when the concrete person has the cemented exactly where the pipe ends. Combined with Mitchell's recommendation, it should be much easier to repair the damage and not have to chip away the cement.

Please keep us updated with your progress, we would be keen to see a photo of the vent pipe once it's been repaired.

If you need further assistance, please let us know.

Eric

[Smithrj]

Hi @EricL 

Thanks so much for the suggestion. I've just picked up the adapter you have mentioned so will crawl under the deck on the weekend to try it out. Also purchased the PVC to PVC Rubber Joiner that Mitchel mentioned, so with these two I should be able to effect some sort of repair.

Regards,

Rod.

[Smithrj]

Hi @EricL & @MitchellMc,

Thanks again for all your advice. Looks like the repair went well. Once I removed some more of the original metal vent pipe to allow for some room, the adaptor fit the ground pipe OK and with the help of a little silicone everything seems to have sealed up properly. Here's a picture of the end result:

[EricL]

HI @Smithrj

Thank you for the update. I'm glad that you got it repaired. I'm sure @MitchellMc will be happy to know that his recommendation was helpful. If you have any other projects on the go, please don't hesitate to post them. Should you have any questions our members would be more than happy to provide advice and information.

We look forward to seeing your next project.

Eric