Shower trap strange goings-on

[AverageDIYerEssex]

Hi all. So I fitted a new shower a couple of months ago and noticed I'm getting a sewer gas smell every now and then. I have checked and it appears to be coming from the shower trap.

Every couple of days the shower looks like the attached image. When I add water or use the shower the smell goes for a bit so I assume that the water is evaporating from the trap and allowing the smells through.

That waste line does have an AAV fitted further along so assume the water isn't being sucked out.

Can anyone confirm this from the images and if so how can I attempt to stop this?

 

[Madrab]

Is the shower on the same waste run as another fixture that is used regularly? if so, there could be back pressure that is blowing the seal out of the trap. What is the depth of seal in the trap for the linear drain?

 

[AverageDIYerEssex]

Hi. Thanks for your reply. It's probably best if I do a drawing in the morning.

Basically I have a soil stack coming up from the ground downstairs vertically. It then elbows horizontally for about 1 metre before elbowing up through the floorboards and joins to the bathrooms' toilet. Before the elbow up is a solvent weld boss. With two 40mm connections. One line runs to the small sink and bath (rarely used) and the other line runs solely to the shower. There is a tee in this line close to the shower trap which goes up into a plasterboard cavity wall with an AAV fitted just in case which I was assume would stop any siphoning. ‍(in the right of this picture)

Second picture is the boss without the 40mm pipes connected. One went in either side.

 

[dilalio]

Every couple of days the shower looks like the attached image. When I add water or use the shower the smell goes for a bit so I assume that the water is evaporating from the trap and allowing the smells through.

Not evaporation in that small space of time. As per @Madrab the toilet flush is blowing and/or pulling it.
Probably a very shallow trap won't help.

 

[AverageDIYerEssex]

Not evaporation in that small space of time. As per @Madrab the toilet flush is blowing and/or pulling it.
Probably a very shallow trap won't helda

Not evaporation in that small space of time. As per @Madrab the toilet flush is blowing and/or pulling it.
Probably a very shallow trap won't help.

Damn. Even though the toilet has an AAV and the line with to the shower has one also?

 

[dilalio]

Damn. Even though the toilet has an AAV and the line with to the shower has one also?

They would stop sucking but not blowing!

Can you access them and cap one, other or both off, to see if it might make a difference? Might work!

 

[AverageDIYerEssex]

I can get to the 4" stack AAV as it terminates in the loft. The smaller one however is in a wall and would have to damage wallpaper to cap it.

 

[dilalio]

I can get to the 4" stack AAV as it terminates in the loft. The smaller one however is in a wall and would have to damage wallpaper to cap it.

Try the one in the loft (bag taped over it will do.

 

[AverageDIYerEssex]

Try the one in the loft (bag taped over it will do.

Thank you will give it a go.

 

[AverageDIYerEssex]

Try the one in the loft (bag taped over it will do.

heyyy. So I looked at the trap with the top off when flushing the toilet and it did move up and down and definately a few mm lower afterwards.

I then did you bag suggestion so nothing in or out there and it's doing exactly the same.

It's so annoying as the main stack has one and so does the shower line, so I don't understand why it's doing it which two AAVs on it!?!? Is there anything else you can suggest?

Thanks.

 

[dilalio]

heyyy. So I looked at the trap with the top off when flushing the toilet and it did move up and down and definately a few mm lower afterwards.

I then did you bag suggestion so nothing in or out there and it's doing exactly the same.

It's so annoying as the main stack has one and so does the shower line, so I don't understand why it's doing it which two AAVs on it!?!? Is there anything else you can suggest?

Thanks.

In-floor horizontal 4" runs are not ideal but sometimes you've got no choice.

Is the whole stack internal or does it emerge from inside to outside at some point?

With the bag on the aav in the loft... Keep flushing the toilet and see if it eventually pulls the shower trap... Run the basin too.

Then remove the AAV (is it pushfit or solvent weld?) and repeat the process.

If it doesn't pull or drop with the AAV removed then you need to vent the stack!

If the only place you can access it is in the loft, then easiest and least disruptive would be to route it up through roof... Send some photos of it in the roof... It's a vent so doesn't really need to be high up the roof pitch... Can be taken over to the eaves.

 

[dilalio]

Another option, if there's room on the shower waste pipe, would be to access it via the ceiling below and fit an inline hepvo (waterless trap fanny trap).

 

[Madrab]

Have you taken the small AAV that's venting the shower run off and then tried it? Put a aquare of toilet roll over the vent pipe and watch it when flushed. Waste/Soil runs can need both positive and negative venting, especially if the run is extended as it sounds like the shower seal is being subjected to back pressure from the flushing toilet.

What is the seal size on the shower waste run? Should be in the traps MI's.

 

[AverageDIYerEssex]

Firstly such comprehensive replies of help thank you so much. I recall you helping me with stuff before so thank you again.

What is mega annoying is that the kitchen ceiling below had massive access holes for months so I could do the pipework and fix any issues for about two months and after thinking everything was ok I recently plastered over it and painted it all. ‍

Is the whole stack internal or does it emerge from inside to outside at some point?

It is all inside until the point of going into the ground.

The 4" AAV is a new one actually as the original (20 years old) was letting smells through. It is just a push fit so easily removed. I have actually removed it to put the bag over.

I did actually wonder what it would do if I just removed the bag all together and left it open yesterday so pleased you suggested trying it. In the middle of each side of my square roof there is actually a venting tile already fitted with a 4" attachment already on it. IF venting this with no AAV fixes the issue, would it be suitable to use a 4" flexi air ventilation type tube to get from the top of the stack to the vent? Either the metal or pvc ones?

 

[AverageDIYerEssex]

Have you taken the small AAV that's venting the shower run off and then tried it?

Unfortunately not as it's within a plasterboard wall. There is air access into the cavity from above but it have to cut a hole in a wallpapered wall to gain access so would be a last last resort if that makes sense.

Put a aquare of toilet roll over the vent pipe and watch it when flushed.

The 4" or the one on the shower run 40mm?

Waste/Soil runs can need both positive and negative venting, especially if the run is extended as it sounds like the shower seal is being subjected to back pressure from the flushing toilet.

What is the seal size on the shower waste run? Should be in the traps MI's.

Please see images attached of the trap.