Our bathroom sink is used multiple times per day but there is a bad odor almost every time we turn on the water, coming from p trap. We have found some bad DIY work in this house already, so I’m wondering if this trap is installed correctly.
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I think you have the same issue as https://diy.stackexchange.com/questions/240049/is-my-p-trap-installed-correctly – Abe Karplus Apr 23 '23 at 22:07
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The simple fix here is to add an air admittance valve above where the P attaches to the drain and becomes an S. Just tee the wall pipe for the P and put the AAV at the very top. – Machavity Apr 24 '23 at 12:57
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@Machavity Don't those usually have a height requirement? Without seeing how much room is between the drain elbow and the bottom of the sink I feel like that's not great advice to be giving. – Logarr Apr 25 '23 at 06:31
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This is not the correct way to install a p-trap. The pipe exiting the sink should run vertically into the top of the p-trap, then exit the p-trap horizontally back into the wall and connect to the sanitary pipe via a sanitary tee fitting.
The configuration in your photo converts the p-trap into an s-trap. S-traps are known to fail due to self-siphoning. Your configuration also eliminates the proper venting of the drain line, which can cause slower draining of the sink.
Unfortunately, it looks like you would need to open up the wall to remove the 90° elbow and reconfigure the piping so that the drain line is horizontal.
pdd
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Technically, the trap installation is just fine. It's the drain stack that has problems. – isherwood Apr 24 '23 at 12:48