Kitchen sink niffs now and again - prevention cures / reason

[fernando]

Our kitchen sink which is about 18 months old and has a d/w and w/m connected the same waste outlet pipe niffs now and again. Can't work out what the smell is. There is no issue with the water running slowly and no apparent blockage. Seems to happen when the d/w has finished but is pretty random.

Any ideas on the reason and suitable preventative measures going forward.

cheers all.

 

[mikeyd]

Sounds like the water trap might be getting sucked dry by the washing machine. Can you describe the pipe layout / type of trap and how close the washing machine connects to it. Or take a picture.

 

[fernando]

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• fernando
• 11 Feb 2009
• 1

The white pipe is the washing machine, the outlet is on the right just before the left bend

The white pipe at the bottom is the w/m outlet. The w/m is about 1m to the left. The in to the w/m is on the right taken directly from the cold water in. If you look at the top, you can see the d/w out grey then black connecting to the sink out.

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• fernando
• 11 Feb 2009
• 1

The pipe at the back (grey then black) is going into the waste and is from the dishwasher

This shows d/w out

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• fernando
• 11 Feb 2009
• 1

demonstrate out

w/m out and in

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• fernando
• 11 Feb 2009
• 1

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• fernando
• 11 Feb 2009
• 1

Thanks for all your help. The wm and dw have been on today and the smell is back! Will check if it appears when the dw is on and the same with wm. Guidance much appreciated.

 

[Symptoms]

fernando - sink & dishwasher empty down via that grey U bend (trap), then into the white waste, then out through the wall via that tee. All is good so far 'cos the sink/dw are protected from foul smells 'cos if that U bend. However, the washing machine waste appears to have no trap before it exits through the wall (unless there's a trap/Ubend in the adjacent cupboard at the bottom of the w/m upstand pipe that we can't see). So my guess is 'cos there's no trap protecting the w/s side the foul air is coming from the top of the w/m upstand. Solution is to fit a trap on the w/m side - these can either be at the bottom of the upstand pipe (that's the one where the waste hose hooks into) or a running-trap positioned somewhere along that lower white waste.

Check the d/w manual for routing it's rubber hose - some say low level then up to discharge, others the reverse. If yours is in the wrong place it may affect the water in the sink trap as mikeyd suggests.

My money's on no trap.

Another solution (and one I prefer 'cos i don't like those hose couplings onto sink wastes) is to create dedicated wastes; one for the sink, one for the washer/dishwasher.

 

[mikeyd]

Yep, agree with Symptoms. And can I just say excellent photos, helps a lot.

You now need to work out if the appliances have a trap (Your sink does), and if they do does it stay full of water. A trap, which I'm sure you know is a bit of pipework between any appliance/sink/bath and an outlet connected to the sewer which is always full of water and therefore stops any smells getting back up the pipe.

Let us know how you get on.

 

[fernando]

ok thanks, i will check the trap on the wm side in the morning. The smell is definately coming up through the sink and from what I can work out the w/m waste is protected as its below the sink waste so the water in the sink waste will stop the smell from the wm or have i got that wrong?. I have had a sniff around the wm and seems ok but will check the trap.

not sure what the routing is but will have a look in the book.

if i was to create individual wastes i guess i only need to do for the dw, which goes in at the top as the wm and sink are covered. where would you suggest i connect the dw waste to allow an out to the sewer.

thanks for the ideas / advice

my only slight concern is this is relatively new and comes and goes so would have thought the problem would have been from outset if the pipes are incorrect?

how do i check if water is in the trap?

 

[foxhole]

The pipework after the unbend is configured to give a syphon effect , can't help wonder why the waste doesn't run to the left and then straight out, lots of unnecessary pipework.
The syphon effect will empty your U bend when the d/w empties.

 

[Symptoms]

fernando - the top of the upstand pipe will be OPEN with only the washing maching rubber hose hooked on so there'll be a space through which any foul air will escape into the cupboards. What you might be sniffing may be wafting-up from here giving the impression that the honk is coming from the sink. To repeat, if the washing machine side has no trap at the bottom of the upstand pipe (in the adjacent cupboard) then you WILL get foul air escape; that U bend is only protecting the sink/dw side. Again, I've never liked coupling into sink wastes, infact we never do it (even if the appliance manufactures and the trap makers provide the bits) - it's good practice IMO to have separate waste pipes thus avoiding syphoning.

Just an additional thought - how often do you 'clean' the pipe innards? The occasional bit of bleach (or whatever you prefer, maybe eco juices) down the hole can help to keep things sweet. You could have a load of festering gunk in the pipe's innards - consider unscrewing the trap (bucket/basin below to catch the foul water in the trap), taking it outside and flush through with the hosepipe (I'll bet there's a load of smelly gunge in there). It all helps.

 

[fernando]

ok, washing machine did have a trap, so took the last advice and unscrewed all the pipes and gave them a clean.....................

found a rather large stone in the sink trap?!?!? Amazinly there wasn't a great deal of gunk but it did smell a bit so will see now if a simple clean and moving the stone makes the difference. thanks for all the advice.