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Repost - Smell from waste pipe

Postby paul_handyman » Fri Jul 09, 2010 7:03 am

I got no replies last time so I will ask again -

I have found quite a few posts about smells from bathroom drainage but all appear to have the smell in the bathroom.
My problem is different in that the smell appears outside in the drain.
I know it is not the drain itself - I have checked that by running water into it from a hosepipe. We also do not get the smell when any of the kitchen waste is run into it.
The smell (like a really foul drain) only happens when the washbasin appears to be used . I have not noticed it when the bath or the shower empties.

The plumbing has been in place about 15 years but this smell has only started happening recently.

I thought at first that it was the outside drain but, as I said, this has now been ruled out.
There is no smell appearing in the bathroom itself.
I have checked the U-bend which is clear.

Any ideas what could be the cause of this smell?
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Postby TheDoctor4 » Fri Jul 09, 2010 7:50 pm

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Postby htg engineer » Wed Jul 14, 2010 6:35 pm

If your getting smells from the drains, then there's a problem with the seal/trap. The seal is made by an amount of water being held in the trap, if the seal is lost - the smells can come back up from the drains.

If all the drains are clear, it could be the fall on the waste pipe - too great and you'll get a suction on the trap and water will be lost - or there's a fracture in the gully/trap - quite common when people try rodding drains themselves, not knowing what they're doing - if the bottom of the trap has been damaged/fractured then the water will be lost gradually. ... ully01.jpg

Picture shows typical gully/drain with trap full of water - forming seal.

Basically if you've got the water seal - you can't get any smells back - unless the water lies stagnant.

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