Moldy Smell Coming From Bathroom Shower Drain
LESLIE: Heidi in Oregon is dealing with a stinky shower. What’s going on?
HEIDI: We have a two-story house. The one shower is in the basement downstairs. It’s a daylight basement but it’s built back into the side hill. And what I’ve noticed is that after showering, you know, you leave the bathroom and you come back in and there is this sour-towel smell. It’s not a sewer smell or a septic smell but it smells like a towel that has been left damp somewhere and it’s just been left to kind of mold or do whatever. But I’ve changed the towels and I come back in the bathroom and I’ve located the smell with my nose and gone right down to the drain. And it’s coming out of the drain in the shower.
TOM: What this might be is something called “biogas.” And when the water drains and it takes with it the soap scum and everything else, you can get germs that are going to grow in that. And that biological material off-gasses and can make horrible smells. So …
HEIDI: Well, that’s what we thought, too, because it’s in both showers: upstairs and downstairs. And we only smell it, obviously, after someone has showered and it was wet. So we’ve taken the grates off, we’ve cleaned with a bottle brush. I look with a flashlight down there and those pipes are – they’re spic-and-span clean all the way down to the P-trap.
TOM: Have you used any kind of an oxygenated bleach down those traps?
HEIDI: No, we don’t do that because we’re on a septic tank and we don’t want to kill all the good bacteria in the septic. And so I’ve been afraid to use anything.
I’ve tried vinegar. I’ve used Lysol spray.
TOM: Well, not so much vinegar, yeah. Well, OK, why don’t you use Borax?
HEIDI: Borax. OK. And pour it down into the drain? Because …
TOM: Well, no, what I want you to do is I want you to get a solution of hot, soapy water with Borax in it. And I want you to scrub the inside of that drain, all the different parts, with a big, thick bottle brush. Get as much of that trap cleaned as you can and see if that reduces it.
And by the way, do you have ventilation in those bathrooms?
HEIDI: Yeah. There’s windows, uh-huh.
TOM: Do you have fans that you could leave on after? Bath fans?
HEIDI: Yes, yes. And we always turn the fan on when we shower.
LESLIE: And keep it on when you’re done?
HEIDI: Well, no. We usually shut it off when we’re done.
TOM: So, yeah, that’s another thing I would change. That behavior I would change. What I would do is I would replace the bath-fan switch with one that’s on a timer or a humidistat. So that after you are done showering and leave the bathroom, it the bathroom exhaust fan stays on for another 15 or 20 minutes.
HEIDI: But we’ll go ahead and try that, then, and see what happens.