Waste pipe in kitchen causing smell

7 Feb 2011
Reaction score
United Kingdom
We have the following waste pipe in a ground floor kitchen:

The white pipe is a connection to our sink/washing machine/dishwasher.

The 10cm brown pipe is connected directly to a sewer chamber outside in a shared alley (the distance to the chamber is about 8 feet). This chamber is itself connected to a deeper sewer chamber, the latter being where the soil pipe from the upstairs bathroom is connected.

The problem we are experiencing is smell and noise in the kitchen when the upstairs toilet is flushed. I suspect there must be an air leak to do with the grey fitting on top of the brown pipe. I'll be grateful for advice on:

What the grey fitting is (is it an air admittance valve)?
Does it seem to be fitted properly - I must admit I pushed it down a bit.
Can I easily replace this fitting?

Ultimately a corner kitchen cabinet will be put in that place and I'd obviously like to avoid any issues after that is done.
Sponsored Links
Yes, the 4" soil stack connecting the upstairs bathroom and deeper secondary chamber is also connected to a section that vents above roof level.

Sorry if it's obvious, but what is wrong with the plumbing? I know it looks a mess as the wall has to be caved in to accomodate!
The grey thing looks like it might be a Durgo/AAV.
Possibly the seal has perished and is letting foul air through.
Sponsored Links
They are both AAV`s - yours is offset - so as the brown pipe is cut into the wall - it`s the better one to fit :idea: The noise /smell may be coming from the sink trap . That`s where you need to look while the toilet is being flushed - then report back ;) also a pic of undersink plumbing would help
Thanks Nige,

Pictures of sink:

The long horizontal white pipe is the connection to the brown 4" pipe.
As you will probably be able to guess, the thinner grey hoses are from the dishwasher (left hose) and washing machine (right hose).

Does it seem correct these grey hoses are connected above the U bend?

Also, regarding the AAV, can this just be pulled up and out, without needing to adjust any screws etc? It's a bit stiff when I try and raise it and I don't want to break it!
the dishwasher waste hose is run wrong. It should be looped up to a high point under the worktop, where the top of the loop is higher than the water level in the sink when full. Where you have got it, dirty sink water, including bacon fat, tea leaves and peas, can flow down that hose into the dishwasher.

The other hose is also wrong, but not quite so bad.
Thanks John, that makes a lot of sense!

Out of interest, I imagine the same principle applies to the washing machine hose - should I raise that using a hook too?
John is right about the hoses - and yes, you can just pull out the aav. smells may be coming from the appliances due to the pipes not being correct . They may have dirty water lurking , the connections above the trap are fine . Also oveflow pipes on the sink can get smelly - bleach will sort this .
Thanks Nige, much appreciated.

My wife tells me the smell from the brown pipe area is definitely a sewer smell, and the smell from the sinks was different (dirty water smell). We've now cleaned the U bends (they were bung up!) and hopefully that will reduce the dirty water smell.

As regards the sewer smell, I will attempt to take out the AAV and refit.
make sure your wife never, ever pours cooking fat down the sink. It can go onto a bit of kitchen roll and into the bin if just from frying bacon, if there's lots, from roasting or chips, tip it into an empty baked-bean can and put in the bin when cold (or put out for the birds)
Thanks John, my wife assures me she would never do such a thing :)

I managed to get the AAV out and refit it - when the top comes off there is a loose round thin disc about 4cm or so diameter (I beleive this is supposed to rise as water drains).

This disc has four holes which takes 4 small spikes fixed to the top. However, it was quite fiddly getting the spikes into the holes (and not sure I've succeeded!) as you can't see what you're doing once the top goes on. Any tips appreciated!

I'm tempted to buy a new AAV which I can just insert - would appreciate recommendations on a good make.
OOI, is that horrid AAV thing just sitting there exposed in your kitchen forever? Or are you currently renovating?!? :eek:
Yes, we basically built the kitchen building and ran out of money for the kitchen itself (':oops:')

When funds allows, we will be building over this spot with a corner unit, but obviously need to ensure access (I understand these AAVs fail now and then).

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links