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Discuss Smell from sink bowl and a half despite putting in new traps and anti syphon?? in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Darren Scott

Messages
13
Hi all, my wife is going crazy over the smell from the kitchen sink...typical drain smell!.

Got bowl and a half in the kitchen, smell comes up from the half bowl when using the main bowl or vice versa. Decided to strip out all the waste from under sink and put new fittings pipework in. Also decided to put an anti syphon in just in case the traps were syphoning when emptying one of the sinks. Told the Mrs that it cant possibly smell now once I had done it...next day it was smelly again, and I couldn't disagree 🤢

Just cant see what may be wrong, hoping this is really obvious to the experienced plumbers and DIY'ers out here. ANY help would be greatly appreciated.

Note, picture has the anti syphon highlighted in yellow, and the outlet to the main drain in red. Other feeds in are from water softener & dishwasher.

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steadyon

Esteemed
Messages
1,025
I can think of only 2 possibilities:
1. The anti-vac valve is stuck closed and the trap is being pulled allowing sewer gas up through the nearest vent - which looks like the small bowl waste.
2. The anti-vac valve is stuck open, and sewer gas is coming up through it.

Incidentally, both appliance waste hoses should be raised up to just under the level of the worktop, then fall down towards their spigots on the waste fitting. If not, you may get stagnant water trapped in the hoses. I think it unlikely this would cause the smells, although it is possible, particularly for the one on the right.
 

Basher

Messages
370
To add to the above - for many years our dishwasher had its own 'standpipe/ trap waste directly to the drain outside.
During recent kitchen refurb, dishwasher has been connected to the sink waste, similar to the OP's arrangement.
The dishwasher waste hose is supported right up to underneath the worktop.
We get a rotten drain smell occasionally, after the dishwasher has run overnight, which seems to be due to the dishwasher waste water sitting in the trap under the sink. I would have thought the dishwasher rinse would wash away anything that smells, but the issue has only appeared after abandoning a separate drain for dishwasher.
Just a pet theory - could be wrong!
 

Darren Scott

Messages
13
I can think of only 2 possibilities:
1. The anti-vac valve is stuck closed and the trap is being pulled allowing sewer gas up through the nearest vent - which looks like the small bowl waste.
2. The anti-vac valve is stuck open, and sewer gas is coming up through it.

Incidentally, both appliance waste hoses should be raised up to just under the level of the worktop, then fall down towards their spigots on the waste fitting. If not, you may get stagnant water trapped in the hoses. I think it unlikely this would cause the smells, although it is possible, particularly for the one on the right.
thank you for your comments, will take a look at those other two feeds. thanks
 

Darren Scott

Messages
13
To add to the above - for many years our dishwasher had its own 'standpipe/ trap waste directly to the drain outside.
During recent kitchen refurb, dishwasher has been connected to the sink waste, similar to the OP's arrangement.
The dishwasher waste hose is supported right up to underneath the worktop.
We get a rotten drain smell occasionally, after the dishwasher has run overnight, which seems to be due to the dishwasher waste water sitting in the trap under the sink. I would have thought the dishwasher rinse would wash away anything that smells, but the issue has only appeared after abandoning a separate drain for dishwasher.
Just a pet theory - could be wrong!
Interesting...our dishwasher has always been like this but will take a look at this as part of the action from the reply above from Basher. thanks
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Messages
30,867
Solutions
2
Where’s the anti vac yellow mark is a rodding eye
 

Darren Scott

Messages
13
Where’s the anti vac yellow mark is a rodding eye
sorry you are absolutely right it is...i marked up the wrong pipe, sorry. here is another shot from a different angle showing the anti syphon...thanks and good spot!
 

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Ric2013

Plumber
Messages
3,597
Can't see any serious pipework issue. My first thought was that there is a lot of pipework on the house side i.e. upstream of the trap. So any dirt in that section could cause smells as the trap will only prevent sewer gasses rising from downstream of the trap.

However, the fact that the pipework is new makes this unlikely - what dirt can there be to smell? The appliance hose theory is a possibility, but I somehow doubt it. Though no harm in removing appliances and blanking the connections temporarily to check this theory.
 

Darren Scott

Messages
13
Can't see any serious pipework issue. My first thought was that there is a lot of pipework on the house side i.e. upstream of the trap. So any dirt in that section could cause smells as the trap will only prevent sewer gasses rising from downstream of the trap.

However, the fact that the pipework is new makes this unlikely - what dirt can there be to smell? The appliance hose theory is a possibility, but I somehow doubt it. Though no harm in removing appliances and blanking the connections temporarily to check this theory.
thanks for the feedback, yes all new pipework so it cant be that. Pretty frustrating given its all been replaced and still smells. Will try blocking off the appliances and see where that lands me. thanks again.
 

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