Smelly bathroom - can't find source & not the AAV

[trickysummer]

Hi

I'm really struggling with a bad sewer gas smell in my bathroom & need any experience or ideas I haven't already tried!

I moved in to a new house (new to me, but 50 years built). It has 2 bathrooms up stairs, the ensuite which is fine, and a family bathroom - which is getting a slight sewerage gas smell almost all of the time. Some days its worse, others not too bad. I've read loads of forum and plumbing advise most which suggest (1) air vent / AAV blockage / poorly fitted / needs replacing - so I've had a plumber replace it; the problem has not improved (2) p-traps under the bath / sink / shower being either evaporated letting bad air in to the room from the soil stack, or need cleaning - I've checked these and cleaned with gallons of bleach over night multiple times - I can't get any sign of a smell from any of them. (3) Blocked or backed up drains - I've lifted the manhole covered and they are really clean, slight smell but nothing you wouldn't expect from a sewer. Water is flowing fine.

The smell is really hard to trace to a specific place in the room it seems to build when the door is closed. If anything it seems to be worse around the loo.

There is no sign of any leak around the soil stack connector to the toilet.

The only thing I have not tried at this point is replacing the fitting from the soil stack to the toilet incase a seal has gone - but most places seem to say these seals are very unlikely to break, and if they do then I would see visible signs of a leak?

Does anyone have any ideas??

The soil stack goes down stairs and a cloakroom loo shares the same stack. That loo does not build up a smell. Nor does the ensuite which is on a different stack, but same drain / manhole.

I'm all out of ideas! More than happy to get an expert in, but at this point the plumber had no other suggestions, and seems unlikely to be a mains drain unblocker service.

I've resorted to a load of diffuser sent bottles which is pretty much just making a cocktail of rancid stench!

Any help would be great! thanks everyone.

 

[Nige F]

What is on the bathroom floor ? Can you get to the boards ? maybe they are holding a buildup of pong over the 50 years - round the loo

 

[kidgreen61]

Last time I went to investigate one of these I found a dead mouse under the floor.

 

[trickysummer]

The floor is tiled with electric heating under, so ripping it up is not really an option for the time being. I can see the loo is attached via a short flexi coupling to the stack, which is just about accessible. If the flexi or stack has some built up waste stuck in it, would that cause this issue? I have been working on the basis the stack must have a crack or broken seal. What is the best way to clean the stack pipe work, which I think would need to be accessed via the toilet flexi.

 

[Hugh Jaleak]

Build up of waste wont be an issue really, unless it stops an appliance from draining properly. If you've odour issues then foul air is getting into the room from somewhere. What is the stack made from? Cast may have possibly cracked somewhere, plastic is less likely to be damaged.

 

[YorkshireMidge]

Are you getting any gurgling from sink or shower or bath when one of them is operated? If they have been plumbed into the same horizontal waste pipe (as opposed to individually into the soil stack) as sometimes happens in older installations, you can get the water being syphoned out of a trap allowing sewer smells out. It can usually be fixed by switching to anti-syphonic traps which have an air valve on them. Where evaporation is a problem (unlikely in this case if its a main bathroom) you can get a completely dry trap called a HepVo - and these are popular in motorhomes and the like, but would also work where syphoning is a problem with wet traps in a house. I mention the HepVo because its very compact and might be an option if there isn't physical space to fit an anti-syphonic trap.

This issue would explain the varied degree of smell - as it depends on how the facilities are being used. i.e. if a trap is emptied, how long before that trap is filled up and the seal is restored by people using that item.

 

[Mottie]

Last time I went to investigate one of these I found a dead mouse under the floor.

That was my thought. A dead mouse definitely smells like a gas leak.

 

[Bodd]

A mate of mine called me to investigate his smelly bathroom in his rented flat.

I took off the bath panel,,,,,,,, cleaner than clean...

I suggested his downstairs neighbour might be dead....

He was.....

 

[trickysummer]

Ok so today I thought I’d try a Hepvo as one suggestion in this thread. Went to install in the basin and found the space was not going to work (very tight 90 degree waste to plug hole pipe work) but I did notice there was an anti syphon trap - and on removing it to clean I found the valve was full of gunge which was preventing it from fully closing. Cleaned and re-fitted. Fingers crossed this was the issue - that waste is joined to the soil stack so perhaps was the cause. I’m hoping so before more invasive work starts. Bath and shower traps are fitted underneath so both require a lot of tiling work if access required...