i recently moved into a new house and installed a new garbage disposal on the kitchen sink that previously didn't have one. while i'm new to plumbing, it went alright, only needed 4 trips to the hardware store to get everything. but now there's the stench of sewer gas from beneath the sink, but i'm positive there's no leaks in any of the pipe i installed. the P trap should be stopping the smell coming up through the pipe, so i'm concerned there's a crack or break down into the floor where i couldn't get to. any suggestions, or should i call a professional to look at it?
Sewer gas from beneath the sink?
- Thread starter jamjim096
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First off, you have is an illegal S-trap. The "P-trap" is not vented.
Second, that corrugated flex that you are using as a 90-degree elbow will be causing you problems. Food particles from the sink will accumulate in the corrugations and foul smells will result over time.
Third, the straight tee you have combined the garbage disposal with the other sink drain is totally wrong. Flow from the garbage disposal is not directed into the "P-trap". Food particles from the disposal will splash over into the horizontal drain form the other sink and will cause flow issues.
Your installation should look something like this.
The tee connecting the disposal to the drain has an internal baffle to direct the disposal discharge down into the P-trap. The P-trap connects to the vertical drain piece with a Sanitary tee. The device on top of that vertical drain is an Air Admittance Valve (AAV). It allows air into the drain so that the flow down the vertical drain does not siphon out the water in the P-trap. The cleanout below the Sanitary tee is also a highly recommended item for such an installation.
Second, that corrugated flex that you are using as a 90-degree elbow will be causing you problems. Food particles from the sink will accumulate in the corrugations and foul smells will result over time.
Third, the straight tee you have combined the garbage disposal with the other sink drain is totally wrong. Flow from the garbage disposal is not directed into the "P-trap". Food particles from the disposal will splash over into the horizontal drain form the other sink and will cause flow issues.
Your installation should look something like this.
The tee connecting the disposal to the drain has an internal baffle to direct the disposal discharge down into the P-trap. The P-trap connects to the vertical drain piece with a Sanitary tee. The device on top of that vertical drain is an Air Admittance Valve (AAV). It allows air into the drain so that the flow down the vertical drain does not siphon out the water in the P-trap. The cleanout below the Sanitary tee is also a highly recommended item for such an installation.
thanks, this is a good guide to go off. i was just trying to copy the old plumbing the previous owners had installed.
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All good advice above but I'll add some to mentioning the trap syphoning because of ALL THAT's WRONG with the installation, especially it being an S-trap and/or not being vented properly. One purpose of a vent, aside from allowing water to drain properly and not syphon out below the trap-weir, is to allow sewer gas to rise up and out above the roof where it dissipates . Even a 1/16 of an inch will allow sewer gas to escape and cause that wunnerful aroma you're experiencing. // Sewer gas is noxious warm air and will rise at first, then, once it cools it will "settle" downward because it's heavier than air. This is why you "may" be smelling the gas under your sink ... though there may be other reasons. // Think of one purpose - there are many - of proper venting like this: Put a straw in a glass of water. Put your thumb over the top and raise the straw. Water will stay in, but will flow when thumb is lifted. // I know folks hate to call professional plumbers, but oftentimes your health, safety, and comfort are more important than saving a few bucks. Any "good" plumber has years of training and is as important as any doctor, nurse, or other health "professional". // Good luck.
Well said Ed............
