Smell coming from external sewage pipe occasionally

[mfmcdonagh]

Hello,

 

I have a problem with a sewage pipe that is coming from an internal toilet. Every so often there is a strong rotten eggs smell coming from the sewage bend in the attached photo when you stand beside it outside. Its not there all the time, but probably correlates with about 10% of the time when someone does a number two in that toilet. It seems the smell is coming from where the bend and pipe join. Should this be happening ? Is it that there is a problem with the seal in the bend ? any tips to fixing this problem would be much appreciated.

[jamieled]

The smell is likely hydrogen sulphide, produced from the breakdown of matter in sewer pipes. The pipes you show have seals in the fittings. Two initial observations:

 

1) I can't be 100% sure from the photos, but those pipes look like they are rated for underground use only, typically supported by bedding material. 

 

2) In an arrangement like that, with an unsupported length of pipe, it's possible that the seal is either damaged through movement or the pipe is not sitting in the fitting cleanly leading to escaping air. This is possibly more likely to be noticed when you flush a loo as it will push air out through any gaps in the pipework.

 

Two things you could consider. First is to try and air test the pipe work, this will let you know if there is a leak. It will depend on how easy access is up/downstream of the pipework. Secondly, you could replace the pipework with appropriately rated and supported external pipework.

[Conor]

That's underground pipe. It's not UV stabilised and should not be used above ground. You want to replace that pipe with either the same type and cover it, or black PVC pipe to ground level bend and cover. It wouldn't be hard to pull those apart and replace. Likely the seals have pulled out or the pipe has become porus. You need to make sure the bottom bend has a duck foot and is set firm, and the vertical pipe is clipped to the wall or a support.

 

Finally, is there a vent pipe or air admittance valve on that branch? From the description it's just servicing a single toilet then presumably connects to the sewer outside.

Edited March 24, 2022 by Conor

[mfmcdonagh]

40 minutes ago, Conor said:

That's underground pipe. It's not UV stabilised and should not be used above ground. You want to replace that pipe with either the same type and cover it, or black PVC pipe to ground level bend and cover. It wouldn't be hard to pull those apart and replace. Likely the seals have pulled out or the pipe has become porus. You need to make sure the bottom bend has a duck foot and is set firm, and the vertical pipe is clipped to the wall or a support.

 

Finally, is there a vent pipe or air admittance valve on that branch? From the description it's just servicing a single toilet then presumably connects to the sewer outside.

 

Thanks Jamieled and Conor

 

When I google duckfoot  bends, most of them seem to be steel ? are you referring to the steel ones ? @Conor

 

There is no vent pipe on this branch

 

 

[saveasteading]

Agreed as all above. It is an easy enough job to change these. have your replacement grey parts ready before you take the brown ones off.

Put an obvious marker, even sign, on the wc or you may get a nasty surprise.

 

change the two bends and the vertical as they are all in the daylight and probably inferior, plus, it will be easier to persuade these off and on with that arrangement.

 

You might need someone in the house to push back and prevent the pipe in the wall going in, or damaging the internal fittings  ...but maybe not.

Expose the remaining ends in the ground before you dismantle it and clean very thoroughly or you might leave muck in the seal, and the smells will continue.

 

Grey pipe is more expensive than brown, but it is the right thing to do.

[Conor]

35 minutes ago, mfmcdonagh said:

 

Thanks Jamieled and Conor

 

When I google duckfoot  bends, most of them seem to be steel ? are you referring to the steel ones ? @Conor

 

There is no vent pipe on this branch

 

 

Sorry, terminology borrowed from my industry. You need one of these, ideally sitting on a bit of cement.

 

https://www.diy.com/departments/floplast-underground-drainage-rest-bend-285123-dia-110mm-l-132mm/81473_BQ.prd

 

Everything before this bend should be black. I'd highly advise adding a soil vent pipe up the side of the house. You'd connect to a T piece coming out of the wall and up to a suitable height away from Windows and openings.

[saveasteading]

Yes,I said grey but the right kind of black is fine too. UV resistant....ask to  make sure.

[Russell griffiths]

If I was replacing that I would do a new soil stack including a rodding eye and a vent pipe. 

[saveasteading]

good thinking

[Mr Punter]

Connect a new stub stack with an external air admittance valve via a branch.  Clip stack to wall.

 

Shopping list:

 

https://www.toolstation.com/mcalpine-vp100e-push-fit-air-admittance-valve/p25541

https://www.toolstation.com/branch-110mm-9250/p31580

https://www.toolstation.com/soil-pipe-110mm-3m/p68433

2 x https://www.toolstation.com/soil-pipe-clip/p80712