Intermittent and annoying Sewer Gas smell in the flat

[Artur Jach]

I’m experiencing an intermittent issue with the sewer gases (rotten onion smell) entering the flat through the bathroom. Very annoying as you can imagine. Bizarrely it “only” happens 2-3 times a week, usually between 6pm and 8pm and it lasts for about 0.5-1h but it then goes away. It seems to happen more frequently in cold weather conditions… but there are exceptions to that.

Some extra detail: We’re on a top floor of a four storey refurbished office building. The neighbours directly below us are not affected by the issue but people opposite sometimes are too. It only ever starts in the bathroom and comes from behind the wall where the vent pipe is.

The plumber sent by the developer came earlier this year, did the smoke tests and checked the installation in our flat. Apparently it’s all fine and the issue must be outside our flat. He mentioned that we share the soil vent pipe with the flat directly below so he went downstairs and “sealed” something in the shaft holding the vent pipe (apologies for the lack of technical know-how and wrong terminology). Then it was fine for four months (summer) and it’s just started again!

I’ve done some research and due to the intermittent nature of the problem it shouldn’t be related to the toilet wax seal or t-trap or air admittance valve for that matter (don’t have any in my flat). I might be wrong though so I don’t want to exclude that just yet. It’s definitely not cooking smells either. No smell on the corridors or in the basement.
The plumbers seem to be out of options (!?) but the issue persists so we need to find the solution. Has anyone come across anything similar and managed to fix it? Could this be related to the usage of appliances/water/waste during the peak times?

Please help.

 

[townfanjon]

These jobs are all potential nightmares mate, first thing I would check is when the smell occurs , get close to and smell , the basin waste, shower waste , and bath waste . If either smells that is the problem. Also
try find out if and where the air admittance valve is, if it's easy to change , and for what it would cost change it for a quality type ( I fit McAlpine ) change it, it's worth a try.

 

[chris watkins]

You need to find out what the plumber did last time to make it stop, if it lasted for four months without coming back it is going to be some kind of seal. Ask the developer to get him back ti fix it permanently.

FYI it is a toilet water seal (not wax) & P or S trap (not T trap) it a dangerous thing the internet. LOL

 

[Jules]

Agree with Chris, maybe the colder weather has caused whatever the 'seal' was to shrink or crack and let the smells escape again. Whatever the last plumber did sounds like a sticking plaster rather than a cure.

 

[Jules]

Agree with Chris, that's a first ! :santa3:

 

[chris watkins]

Agree with Chris, that's a first ! :santa3:

I new I would wear you down in the end Jules !!!:wub:

Can we have babies now ?

 

[oz-plumber]

When you notice the smells, go to each of your appliances / fixtures and see if you can hear bubbling from any of the wastes.
Look at the water seal in the pan and see if it raises or lowers.
You don't need much of a sewer smell from a broken trap seal to be more than noticeable.

It definately sounds like a venting problem, but being on the 4th floor and a combined stack, the possible causes are numerous.

 

[stevetheplumber]

probably a durgo(aav) hidden in the wall cavity somewhere

 

[Reg Man]

Water seals not only on wc, but on all water traps on the waste system. May be poor design of waste system sucking the water out of a trap. Look at anti-siphon traps or venting the waste system

 

[Artur Jach]

The plumber that came last time said he doesn't know what else he can do and gave up. The developer is sending the company that has done the initial plumbing work in the building. They are coming next week. I'll now have more in my arsenal when talking to them so thank you all.

townfanjon and stevetheplumber - the smell only comes from behind the wall where the vent pipe is and also from behind the toilet next to that wall. I was told by the previous plumber that there is no AAV installed in my flat.

Should I ask the new plumber to check again for AAVs in my and other flats?

chris Watkins and Jules - I'll definitely make sure the new plumbers go and revisit whatever the other guy sealed. I’ve read somewhere that it can also be caused by not sealing the vent pipe connections properly – do you think this could cause this and worth exploring? Thanks for the correction too... I wouldn't want to be talking *!"£$% to the pros.

oz-plumber – can’t see or hear bubbling from any appliance/fixture in the bathrooms BUT sometimes I can hear a gurgling sound when using the kitchen tap and washing machine (in the kitchen too).

Could this be related?

Reg man – interesting, will mention that to them

I’ve also read that it could be related to the vent stack leak and I would need to do the “pressure test” to see where it is. Would you say this is worth doing and could this cause the smell to appear only during the peak time?

Also, do you think that getting an independent plumbing company (not sent by the developer) could reveal more (potentially unbiased) ideas?

 

[Reg Man]

As it is intermittent and at peak times my money is on poor design sucking a trap out somewhere. You can get anti siphon traps as a cheap fix for poor design.

 

[Jules]

As it is intermittent and at peak times my money is on poor design sucking a trap out somewhere. You can get anti siphon traps as a cheap fix for poor design.

Co-incidentally I went to a flat today where the smell turned out to be caused by the washing machine in the kitchen emptying and sucking water out of the basin trap in the bathroom. Fitted anti syphon trap to basin to prevent this. Could this be your problem ie do you have washer or similar on 2-3 x a week?

 

[Jules]

I new I would wear you down in the end Jules !!!:wub:

Can we have babies now ?

Haha! Wouldn't want to ruin such a beautiful relationship tho.......arty: