Smelly drains - advice please


20 Jun 2009
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United Kingdom
Hi all,

Looking for advice regarding an intermittent sewer/drain smell in our kitchen that we can't get rid of please!

We have a 12 year old townhouse and over the last few weeks have had an intermittent smell in the kitchen coming from the sink and the part open top back of the kitchen lower cabinets next to the sink, washing machine and dishwasher. It smells like drains/sewers (eggy smell). Really bad in the cupboard. Never had this issue in the 5.5 years we've lived here. Other neighbours don't have this problem so don't think it is external main drains for the street.

If I am running the hot water tap for a while I can smell it quite badly and don't understand if/how smells could be travelling through the u bend trap..?

This is everything I've tried so far:

  • Poured drain cleaner in kitchen sink left for several hours
  • Removed and cleaned out the gunk under the sink plugholes
  • Cleaned out all the pipework under the sink and checked the seals appear fine (but maybe pipework/seals need replacing?)
  • Drained water out of washing machine, checked the drain hoses from washing machine & dishwasher (they smell fine) for any blockages and ran a fishing tank pump hose brush up them to clean the hoses
  • I clean the washing machine and dishwasher using cleaning chemicals on a hot wash every 1-2 months anyway and wipe washing machine after use to prevent mould and bad smells
  • Checked for any leaks of cleaning products / dead mice/animals behind the cupboards
  • Taken cups of the cold and hot water out of the room and smelt to check it isn't an incoming/hot water tank smell problem - it definitely isn't
  • Cut out the boxing for the drain pipe adjacent to the kitchen cabinets to look for where the pipe joins the soil vent stack - it's hard to see as it is in the wall cavity but looks ok
  • Had a drain company out to check the external drain inspection points - they were clear but gave the ground level system a flush out to the main sewer in case anything was backing up. When we ran a tracer we found that our bedroom ensuite sink and shower run through the same train - more on that shortly...
  • There have also been some intermittent smells from the bedroom ensuite bathroom sink
  • When I flush the toilet in the ensuite bathroom I find sometimes the shower drain will bubble/gurgle. I'm trying some drain cleaner down those now
  • I have gone up into the loft to look at the vent pipe. It terminates in the loft space with an air admittance valve - Osmavent 110. When I flush the toilet I can hear a whoosh so I think it's working as it should but it is removable easily (not solvent welded in so easy and relatively cheap to replace). Didn't smell terribly when I removed it temporarily.

As we haven't had this problem before, I assume that the pipework layout is sound and it is just something that needs replacing that isn't working as it should (wear and tear etc...) or a blockage somewhere....?!

Any ideas would be gladly received to finally banish these intermittent smells. Numerous plumbers and a drain company I have contacted for help have said everything I've tried is exactly what they would do and they had no further suggestions to fix this issue.....

Thanks all!
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A durgo valve on your soil stack - Osmavent 110. ****things are always causing trouble. get the pipe through the roof to open air. Numerous plumbers......:unsure:. Hugh from T'North or Andy from Hertfordshire and others here will probably agree with me;)
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Hi thanks for your replies!

The kitchen sink has 1.5 bowls

No overflow fitted to sink when it was installed (previous owner)

The back of the kitchen cupboard smells really badly of rotten eggs this eve again. Intermittent. The sink waste goes along behind it then into boxing to the soil stack (I opened the boxing earlier to check for leaky or split pipe). I pulled out the washing machine and can't see any leaks etc. Had a washing machine engineer check the washing machine and dishwasher today just to rule it out of desperation but said they are fine it is definitely a drain smell issue....

Is it worth trying to change the AAV in the loft??
Here's photos of the sink


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Take off the AAV in the loft and flush all toilets to check correct operation. While you are they fit a new one.

  • Thanks
Reactions: LL
Thank you so much Andy will give that a try

Is there a brand you would recommend replacing it with? The osmadrain has a 10yr warranty and good reviews online. We would prefer not to get a hole in roof to vent to the outside and just ensure the AAV is working as this is only a recent problem.
The hole in the roof is the best option but would incur other costs, so best option would be to replace with the Osmadrain, order online and refit.

  • Thanks
Reactions: LL
Thanks so much!

Ps I see that you are local. I'm based in North London. Will save your details in case need them.
Hi all - I thought I'd feedback after replacing the Osmavent 110 in the loft with like for like (good reviews, 10 year guarantee).
Fingers crossed but after a week not a single smell from the drains and cupboard, so hopefully changing the AAV in the loft has finally sorted it!!
Thanks all esp Andy for the advice :)
Hi all - I thought I'd feedback after replacing the Osmavent 110 in the loft with like for like 10 year guarantee).
Well you've got 10 years - then go through the roof with it ;)

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