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Greg H
Sewer gas smell

A few months ago I replaced a leaking faucet on my bathroom sink (located in the master bedroom). As part of the job, I also replaced the drain tailpiece, and P-trap. A few days later, I noticed that when running the water (usually slowly), a bit of sewer gas would come up from the drain. It happens nearly all the time, but clears up after a few seconds. What's odd is that there is no smell at any other time; i.e. if no one turns the water on, there is no smell. It's only during the first 5-10 seconds after turning on the water.....then it goes away. I replaced the P-trap with another new one, but the problem still remains. Before I changed out the faucet, we had never had any problems like this. And we have lived in the house for 22 years. About a month later, I remodeled the main bath which is on the other side of the wall from the aforementioned problem sink. As part of the job, I replaced both faucets in a double sink along with the respective tailpieces and P-traps and have had no problems. I would imagine that these faucets share the same main soil stack with the problem faucet, but probably have separate vent lines. Any ideas?

Re: Sewer gas smell

Did you by any chance shorten the tail piece any??
The "u" trap should be at the lowest part and level so that the water in the trap is always full..which prevents gas from coming up the drain...new water forces out old water in the trap at a constant rate. If the tail piece is shorter then it would give a pitch to the trap and the gas would have an avenue for which to travel....try extending the tail piece and lowering the "u" trap a little more to keep more water in it...since that is it's function.
Hope this helps

Greg H
Re: Sewer gas smell

Thanks for the input. I did not shorten the tailpiece when installing the new P-trap and the trap itself is dimensionally the same as the old trap....i.e. the setup is exactly the same as before. However, since the smell is sporadic and only occurs from time to time, even the slightest change could be important. Thus I like your suggestion of trying to trap more water by effectively dropping the P-trap relative to the tailpiece as well as relative to the the horizontal drain line which goes into the wall. I'll try to figure out how to do it.

Re: Sewer gas smell

You need to check this sewer to technician which give you better ideas for this purpose.

Re: Sewer gas smell

I dont think a shorter tailpiece would be the problem here. Most under counter p-traps have at least a 2" water seal. If you shortened the tailpiece enough to drain the trap it would have to be at such a steep angle it would not hook up. I would suggest closing stopper and turning water on. Then see if you still get smell.

Re: Sewer gas smell

Blame the dog, it always works for me! :)

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