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In late June I had a new kitchen sink. Some time (6 weeks ish) afterwards it started to smell when I drained a load of water away. Smelly air being forced up the overflow. Is there anything wrong with the plumbing? I've sent loads of noxious chemicals down it but that hasn't made a lot of difference. Note, the grey flex is the washing machine drain. The white flex goes up to the overflow.

Expert advice much appreciated.

Ian,
get rid of the slack in the white hose from the overflow. It's basically acting as a U-bend and water is trapping there and going nasty.
The proper u-bend will stop any smells coming up from the drains so you don't need two. Also the proper u-bend will get water flushing through it everytime you turn the tap or washing machine on so it wont stay in the trap long enough to go stagnant whilst the water in the overflow waste will just sit there and build up scum until it starts to smell.
If it's not that, stop washing your willie in the sink for a few days and see if that stops it

Pete.l

First of all I'm not a qualified plumber, although I have done a fair amount of plumbing over the years which include fitting many new kitchens where I did the plumbing myself.

Looking at your photo's I would say your sink overflow waste pipe is too long. Due to that you have a self made trap (where I have put the red oval marker in the photo) where dirty water from the sink is being held, that would lay there and only be flushed through when the sink is filled up and water is going down the sink overflow again. That water being held there would go stale, then when you empty the sink the water going down the main outlet would push the smells back up through the sink overflow pipe.

You need to cut the sink overflow pipe shorter so there is no trap, it will then empty when it has water going through it.

Chris.

Oops two minds think alike
By the time I got the photo sorted out and posted it with my reply Pete had beat me to it

Chris.

Yep I also agree, loose the overflow slack


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Only flush coffee grounds down the sink, never tea.
It's the "sissy tea" that causes the problem on this forum, every time.

Thanks guys. I suspected that may have been the problem. And, I can assure you, only coffee grounds and willie cheese go down the hole.

Ian,
Yes the above mention of the overfkow hose being too long will cause a problem but I would also say that the connection to the washing machine/dishwasher should be past the u bend and not on it. As you empty out a full sink, water will flow down this also and just sit until you use said machine. Most modern machines also have traps in them, so all full of washing powder gunk mixed up with washed tissues etc. We all know these stink up and thus smell will travel back up your sink rather than out the drain.

grumpyfrog wrote: ↑Fri Nov 22, 2019 9:07 pm Ian,
Yes the above mention of the overfkow hose being too long will cause a problem but I would also say that the connection to the washing machine/dishwasher should be past the u bend and not on it. As you empty out a full sink, water will flow down this also and just sit until you use said machine. Most modern machines also have traps in them, so all full of washing powder gunk mixed up with washed tissues etc. We all know these stink up and thus smell will travel back up your sink rather than out the drain.

Hmmm, good point!