Drain smells through shower waste

[RB321]

Hi,

Would appreciate any advice regarding an issue I am experiencing:

• The soil stack in the picture serves a bathroom in my house.
• It goes into the drain below ground (which is clear and runs OK).
• It feeds a single bathroom (toilet, shower, bath and sink) - each pipe can be seen in the pic
• All pipework inside is hidden behind stud (and tiled) walls and tiled floor - the only exposed pipework is on the outside.
• There is another bathroom on the other side of the house, fed by another soil stack (but ultimately going into the same drain) - this isnt having any issues.

So, the issue....

When showering (especially after a few minutes) there is a strong drain smell in the bathroom.
I assume that this is coming up through the shower trap.

I have read a few previous posts and it sounds like there should be a durgo valve on the soil stack? It could well be that there is a faulty one in the cavity where the soil stack enters the house - but it is impossbile to get to this without removing tiles and stud wall.

My question is... is there anything obvious that I could do externally to resolve this? i was thinking that maybe the stack needs to be vented or have an air admittance valve installed - but I have no idea if this is correct or where this would be attached.

For example, could I tee the shower drain (1 of the 3 horizontal pipes) and install a durgo valve above it (sorry - this idea may be stuipid!)

Any advice would be really appreciated!

Thanks
Richard

 

[CBW]

If the other stack is vented, I wouldn’t think this one would require additional. Is it only the shower affected? Have you cleared the hair trap? It could be that it runs uphill slightly.

 

[Hugh Jaleak]

Air Admittance Valve (Durgo) wont be inside the cavity, if anywhere it should have been fitted externally. Is the ection of stack in the picture a vertical or horizontal run? I am assuming vertical at the moment, so the bend going into the wall should have been a junction, and the soil pipe continued up the wall slightly outside, with an AAV on the top. Not usual (or good) practice not to fit an AAV or vent the stack, so given that misdemeanor I have to wonder if there's an underlying problem internally with the waste pipework that may be causing the issue.

Using the shower should keep the trap full of water, which would prevent any foul air coming back into the room, unless the shower waste is running full bore and possibly siphoning, but I'd expect the trap to be refilling too quickly to really cause an issue, and even then an AAV on the stack wont solve a siphonage issue in a branch pipe. Do you get any gurgling from any of the appliances in that bathroom when the WC is flushed?

 

[RB321]

If the other stack is vented, I wouldn’t think this one would require additional. Is it only the shower affected? Have you cleared the hair trap? It could be that it runs uphill slightly.

Thanks for the reply.

The other stack is on the other side of the house and joins into the sewer in a different position (not sure if this make any difference). I had assumed that a durgo valve on that stack wouldnt have much impact on this one?

It is only noticeable when the shower has been used (and usually when its been running for a while). The trap is clean and Im pretty certain the smell is sewer gas rather than coming from any debris in the pipes. Put loads of cleaner down there recently, just to be sure.

 

[RB321]

Air Admittance Valve (Durgo) wont be inside the cavity, if anywhere it should have been fitted externally. Is the ection of stack in the picture a vertical or horizontal run? I am assuming vertical at the moment, so the bend going into the wall should have been a junction, and the soil pipe continued up the wall slightly outside, with an AAV on the top. Not usual (or good) practice not to fit an AAV or vent the stack, so given that misdemeanor I have to wonder if there's an underlying problem internally with the waste pipework that may be causing the issue.

Using the shower should keep the trap full of water, which would prevent any foul air coming back into the room, unless the shower waste is running full bore and possibly siphoning, but I'd expect the trap to be refilling too quickly to really cause an issue, and even then an AAV on the stack wont solve a siphonage issue in a branch pipe. Do you get any gurgling from any of the appliances in that bathroom when the WC is flushed?

Thanks for the reply.

The stack is vertical (sorry - i think the photos are rotated) - so the bend going into the wall is at the top.
The pipework inside the cavity is pretty simple as I remember - each drain (toilet, shower, bath and sink). The shower is furthest away from the stack so the fall is probably not as much as it could/should be.

I did think that maybe I could remove the 90 deg bend and extend upwards a bit and stick a valve on the top. The issue is that the bend is embedded in the render - and also disturbing the bend could mean having to smash the internal wall out to get in to fix it. My only hope was there is a way of adding a valve to the outside somehow - but it sounds like you dont think this would fix the issue anyway?

Looks like there is no obvious/easy fix!

Appreciate your help