Gurgling shower when toilet flushed and no roof vent for stack

[James1979]

Since yesterday, we've developed a problem of slow draining toilets (there are 2) and when either is flushed, the water in the shower trap gurgles up.

Looking on Google, the most common cause of this seems to be a blocked vent pipe but we don't have one - we only have an AAV fitted on top of the stack which (unfortunately for him) is in my son's bedroom!

I've taken the top of this but don't know what I'm looking at to tell if this is broken / faulty or not?

How can I tell if this is the issue and if it's not this, is it a blockage somewhere in the soil pipe? Would plunging or a plumber be the best bet if so?!

Photo and diagram below...

Thanks in advance

 

[HERTS P&D]

Pull the top off and see if the toilets flush correctly.

Andy

 

[HERTS P&D]

Please note, your son's room will smell.

Check the outside manhole.

Andy

 

[Bodd]

AAV is not high enough. Yet I doubt thats the problem.

Wait till your sons gone to school.

 

[Bodd]

Please note, your son's room will smell.

Check the outside manhole.

Andy

Am I right in thinking that two AAV's can pull and suck on each other.

 

[Bodd]

Are you end of terrace....... If the whole row goes on AAVs someone will suffer.

 

[James1979]

Thanks - I thought I had pulled the top off (and a rubber diaphragm under it) but obviously not so will try again. Son’s a 16 year old teenager so the smell will just blend in with the others in the room probably!

Detached house so no issue with terrace AAVs. Will pull top off in Morning and see what happens

 

[Bodd]

Detached house so no issue with terrace AAVs. Will pull top off in Morning and see what happens

Your posh!

 

[James1979]

I wish! My house stinks of drains and poo water is coming up through my shower drain!! Not that posh

 

[Bodd]

I wish! My house stinks of drains and poo water is coming up through my shower drain!! Not that posh

Blame your son

 

[HERTS P&D]

I wish! My house stinks of drains and poo water is coming up through my shower drain!! Not that posh

Is the shower on the ground floor?

Andy

 

[James1979]

No - all on first floor. We’ve had a new soil pipe installed downstairs ready for a new downstairs toilet with a new chamber attached to the existing manhole (Still just the pipe sticking out with no toilet fitted yet!) But that was done about a month ago and problem only started yesterday so don’t think it’s linked.

 

[Hugh Jaleak]

No - all on first floor. We’ve had a new soil pipe installed downstairs ready for a new downstairs toilet with a new chamber attached to the existing manhole (Still just the pipe sticking out with no toilet fitted yet!) But that was done about a month ago and problem only started yesterday so don’t think it’s linked.

I do... A month would be about right possibly. My money would be on the Builder has lost a lump of something down the drain in the process of doing your work. Initially, the waste would get by, then slowly starts to build up, with the water probably still soaking through and getting past, until eventually it blocks solid. (i.e. now.)

All the signs point to a blockage somewhere, basically now, when you flush the WC or discharge some water, the air trapped in the pipework between the WC and the blockage needs to be displaced by the water, so is looking for the easiest way out. Which seems to be your shower. If you remove the top from the AAV, this may release any trapped pressure in the system, but wont solve your blockage.

Have a look down the manhole, if that's clear, then look at getting it rodded or jetted upstream towards the house and see what comes back.

 

[Madrab]

Another point is that if you are detached and only have one stack running to the chamber then you really should have that stack vented, not sealed with an AAV.

A stack needs to vent positive pressure as well as negative and as long as the only stack has an AAV then there would be no where for any positive pressure to go, if it doesn't, when there's a restriction/blockage then it'll start to blow traps. Especially if you have that much running on a single stack.

Is it just the shower on the the same horizontal run that blows, or does the bath on the other side blow too? (the lowest/shallowest traps would usually blow first, depending on where the restriction is in the stack)

 

[James1979]

Hi - thanks for the last two replies - they both make sense and are very possible. I thought it seemed a bit dodgy only having an AAV so will look at installing a vent - don't think it should be too tricky as it's a flat-roof above the AAV. It is only the shower but, like you say, that's the lowest trap so it would make sense.

Weirdly today, it seems to have stopped blowing after about midday and the toilets seem to be draining better so I wonder if there was a blockage that's now been pushed through and out?