Odor from Bathroom Drains: What’s the Cause?

LESLIE: Wayne in Iowa is on the line with a septic issue. Tell us what’s going on.

WAYNE: Well, when I take a bath, I have odor when I drain the tub. If I take a shower, I have no odor when I take – when I take a shower, obviously, I don’t plug the drain. But everything runs through down to one pipe, which goes out to a septic tank. I do know the line is good from the house to the septic tank because I had to dig that up before I ever did any of the plumbing in the house. I did not replumb the drain on the tub but otherwise, the house has new plumbing throughout.

TOM: So we don’t think that it’s in the drain line. For example, when you talk about sewer odors, the first thing you think of is a missing trap. But if the plumbing has been redone, it’s not likely that that’s the case, correct?

WAYNE: No, it has a trap. And it doesn’t leak into the basement but I – whenever I take a shower, it works fine. But if I take a tub bath and pull the plug on the drain, I get a sewer odor in the hallway outside the bathroom.

TOM: Because the other cause of those odors is something called “biogas” – is when you get a lot of bacteria that can form in a drain. And it may not even be the drain of the tub; it could be the drain of the sink. I presume there’s a sink in that same bathroom. And sometimes, even in the overflow channel of the sink, you get this bacterial buildup that can have just an awful odor to it.

And the solution there is to thoroughly clean it with an oxygenated bleach so that you kill that bacteria, flushing out the overflow channel, scrubbing the drain with almost like a bottle brush to make sure that all of that bacteria is eliminated.

Biogas can be very pungent and unpleasant to live with but relatively simple to get rid of once you get to the spot where it exists. Will you give that a shot?

WAYNE: Yes, sir. I most certainly shall.