Smelly kitchen sink drain

[dogfonos]

Had a new kitchen installed in 2017 which included a double bowl s/s sink with new drainage plumbing beneath. Since early on, there's been an unpleasant smell coming up through both sink bowl plugholes. I haven't used expensive "foaming" type cleaners but the usual disinfectant, bleach and detergent based cleaners knock the smell back for a week or two before it returns.

Late last year, I dismantled the drainage plumbing beneath the sink, cleaned it thoroughly and reinstated it. No smell for a few months but now it's back. I'd rather not disassemble the drain pipes 3 or 4 times a year or resort to expensive cleaning agents - I'm looking for a more permanent solution.

The plumbing beneath the sink connects the two bowls and the drainage from a dishwasher before reaching the U-bend. This means there's a couple of feet of near horizontal pipework connected to the bowl outlets prior to the U-bend. This seems to be the source of the smell. Would it be a good idea for me to fit a U-bend (or bottle trap?) directly beneath each bowl drain then allow the pipework to join afterwards before joining the dishwasher drain and then a final U-bend through which all drainage will pass?

Guidance and opinions appreciated.

 

[HERTS P&D]

Squirt some bleach down the sink overflow.

Andy

 

[undertrained]

From the sound of it you have that pitiful excuse for a waste sysytem, which I can’t stand. I would fit (space permitting) x2 p or s traps and onto a tee section to wastepipe.

A photo might be useful.

 

[Hugh Jaleak]

A photo might be useful.

Yes, we like pics. Always handy to see exactly what's what, as there is no telling what sort of contraption you've got and what needs to be done to sort it out. A properly installed sink waste shouldn't stink.

 

[KenGMac]

dogfonos, good evening.

Possibility that the "two foot" of near horizontal pipework is allowing food waste to build up just enough to allow even a small volume of residual waste solids to [if you excuse the expression] slowly cook / ferment and hence the smell?

As above, if space allows a trap below each sink outlet should prevent the odour?

Ken

 

[dogfonos]

Thanks for the feedback. As suggested, a photo. Note: the sink is designed with no overflows fitted to either bowl. The coiled grey flexible tubing is the dishwasher drain.

This won't be the first bit of plumbing I've had to rectify.

 

[undertrained]

Yes so looks like you have space to rectify, although trapped, it's a while after, so smells will get through. I would definitely recommend altering it to prevent smells. 2 traps (x1 appliance - reutilising existing) a tee and some elbows. Also sort drain hose, shouldn't be trailing

 

[KenGMac]

dogfonos, good evening.

This might be worth a look?
Uniwaste™ Waterless Waste Space-Saving Trap for Basins, Baths ...

https://www.tapwarehouse.com › ... › Wastes & Plumbing Accessories › Bottle Traps

 

[Hugh Jaleak]

Before you do anything else, lift that dishwasher hose up, and support it. Any appliance discharge hose should rise up, then fall back down to the drain point, it will currently have a load of dirty water trapped in it, and could well be causing the stink. Waste setup isn't ideal, but I've seen a hell of a lot worse.

 

[John D v2.0]

Agree with Hugh, that dishwasher hose is wrong and the sink could be draining back into it. I'm not a fan of hoses straight into the sink trap due to noise either, if you put an appliance trap in under there somewhere it would help all round.

 

[dogfonos]

All replies appreciated, thanks.

Before you do anything else, lift that dishwasher hose up, and support it. Any appliance discharge hose should rise up, then fall back down to the drain point

Agree with Hugh, that dishwasher hose is wrong and the sink could be draining back into it. I'm not a fan of hoses straight into the sink trap due to noise either

Also sort drain hose, shouldn't be trailing

Guilty. I fitted the new dishwasher earlier this year and as the smell started over a year ago, the dishwasher probably isn't contributing to the stench - yet. I understand what you mean about the possibility of the sink waste water draining/syphoning back into the dishwasher but there's no sign of that at present. As suggested, I will improve support for the dishwasher waste water hose though (and raise the hose as high as possible in the process). I don't understand what's meant by the hose shouldn't be trailing? It's a flexible trailing-type hose, isn't it?

I appreciate your views on hoses connected directly to a sink trap without venting but I'm not keen on adding an open vent arrangement beneath the under-sink cupboard unless I start getting back-syphoning problems into the dishwasher - though I had such an open vent arrangement for a washing machine in my old kitchen for 20 years without problem or serious smells.

Time for a bit of PP origami!

 

[dogfonos]

dogfonos, good evening.

This might be worth a look?
Uniwaste™ Waterless Waste Space-Saving Trap for Basins, Baths ...

https://www.tapwarehouse.com › ... › Wastes & Plumbing Accessories › Bottle Traps

Interesting product I didn't know existed. I'll bear it in mind for the future but there's room beneath my sink for more conventional (and much cheaper) plumbing options.

 

[Hugh Jaleak]

Hoses are fitted for ease of installation, but still need to be set up correctly. The machine will pump out as required, but it is designed to pump straight upwards, and once over the high point, the water drain away by gravity. This also prevents dirty water from other discharges finding its way back into the machine.

The drain hose also offers the facility to empty the machine, should a fault develop and it stop mid cycle, still full of water.

 

[undertrained]

What I meant by it shouldn’t be trailing, is it shouldn’t be trailing on the floor and be lifted.

 

[Harry Bloomfield]

I have a similar smelly sink problem, with a P trap directly below a 1 plus 1/3 kitchen sink - nothing else going into it. Bleach and /or cleaning it all out, seems to stop the smell for a while, but not for long. It passes straight through the outside wall then slopes down to a gully. I have cut the cast - iron cover, to allow the pipe to discharge below, to avoid the cover becoming obstructed with waste debris. I'm thinking to block the pipe end, then fill the entire system up to the plug holes, with bleach..