Has one of your indoor drains started to have a funky smell that reminds you of the sewer? There are a few potential causes for the smell with easy solutions that you can attempt. But it's always worth having a plumber come out to check after the fact to ensure there isn't a need for a sewer line replacement or advanced drain repair.
Here are a few tips for fixing a sewer smell coming from an inside drain.
Check the P-Trap
Traps in a plumbing context refer to how the pipes beneath the sink are curved to prevent sewer gases from coming up into your sink. Older homes might have what's called an s-trap, which involves the pipes coming straight down, curving up, then back straight down – in roughly the shape of a sideways "s." But s-traps weren't terribly good at the job and are now forbidden by most plumbing codes. If you do have an s-trap, save yourself some time and simply call a plumber now to replace it with a p-trap.
Your sink more likely has a p-trap, which follows the same initial curve as the s-trap. But instead of then turning down into the floor, a p-trap continues straight ahead into a vertical vent pipe. That vent pipe offers a straight shot for sewer gases to pass through without needing to involve the sink pipe at all.
To make sure your p-trap is working optimally, get under the sink and ensure that there aren't any cracks or loose connections along the sink pipe and the vent pipe. You can also check to see if the vent in the pipes is blocked. Simply fill up your sink with the stopper in. Remove the stopper and listen to hear if there's a gurgle while draining. A gurgle means there's potentially a blockage in the vent. Let a plumber handle that part.
Moisten the P-Trap
If the faucet is in a seldom used sink or bathtub, the p-trap can become overly dry and thus offer less resistance to the sewer gases in the vent pipe. You can rectify this problem by pouring about half a cup of mineral oil down the drain. The mineral oil provides moisture and lubrication that should make the p-trap fully functional again.
Note that mineral oil is not the same as olive oil. Olive, canola and other cooking oil can spoil and you really don't' want to add that problem into your sink area.
For more information, check out companies such as Shanks A & G Plumbing & Heating Ltd.