Remind me to get a dog and teach it to sniff out mold.

January 26, 2009 9:21 PM

When I get in the shower I smell that earthy smell associated with mold. Help me figure out what the source may be!

I first started noticing this smell around the time that I foolishly for some reason decided to dump some vacuum cleaner dust / dirt down my shower drain. Not a lot of it, but I quickly realized that maybe this sandy material may not so easily flush through the drain. This may be a red herring however.
I use warm water in my shower and there may be a possibility that something is originating from the hot water tank but I don't smell this from any hot water source outside my shower.
I popped the lid off my shower drain and used a bottle brush with some bleach toilet bowl cleaner to remove all of the buildup of gunk above the water trap. This took the edge off of my mold sensitivity but unfortunately the earthy smell is still there when I get into the shower.

posted by GleepGlop to home & garden (12 comments total)

Use your nose - without running the shower, sniff the drain. Does it smell moldy? Then that's where it is.

To nuke the mold in the drain, I'd try a dilute bleach solution. Pour it in, let it sit for 15 minutes, then flush with hot water. Open a window for ventilation and keep your face away from the drain while doing this.
posted by zippy at 9:51 PM on January 26

I don't think mold growth within pipes/drains is very common. It's more common to have a problem on the drywall or in the air duct system. Other potential sources of the moldy smell might be mold growing within the bathroom walls (a leak from a pipe, condensation on the outside of a pipe), on the walls (whether visible or not), on the shower curtain, on towels in a cabinet, so on. That said, it could be growing on something inside the pipe. And if that's where the smell is coming from, that's probably where the mold is.

Mold needs a surface to grow on, organic material (like dust or wood or drywall or paper) for food, and moisture to grow. You can make conditions less favorable by increasing the air flow in your bathroom and lowering the humidity.

Also, bleach isn't a perfect solution to mold problems--it sometimes works and sometimes doesn't, depending on the surface and the application. Borax and boric acid are good mold fighters, and more dependable than bleach.

In your situation, I would:
* check the bathroom thoroughly for water leaks
* start running fans and opening the window to get better ventilation in the bathroom
* try the bottle-brush routine again with a borax solution, allowing it to sit for a while before scrubbing.
posted by aka burlap at 9:55 PM on January 26

and yeah, you might be allergic to this kind of mold, or it might be one of the kinds that isn't good for people, so put on a dust mask or something while you're scrubbing.
posted by aka burlap at 9:57 PM on January 26

I don't think mold growth within pipes/drains is very common.

I would agree, and I would lean towards the drywall thing too, except for the dumping of the vacuum cleaner bag down the drain. (Really, don't do that.) Could be that it clogged up in a bend, further down than your bottle brush, and is moldering down there.

After using your nose as advised above, if the smell seems to be coming from the drain, try the baking soda/vinegar/boiling water cure to loosen whatever gunk might be in there. Then try the diluted bleach.
posted by mudpuppie at 10:03 PM on January 26

Seconding the possibility of the smell coming from the shower curtain, especially the very bottom edge. Or if you have a shower door, do you scrub it as well or as often as you do the rest of the shower enclosure? Our older glass shower door gets stinky fairly quickly.
posted by peep at 10:13 PM on January 26

The drain doesn't smell when I sniff it. The earthy smell is 'activated' once the water starts coming. I think the water is loosening the offending particles into the air wherever they are coming from. My shower stall with a glass door gets cleaned regularly but now that I think of it the actual sliding door part at the bottom is somewhat scuzzy so that is something I will have to check into.
When I look down the drain with a flashlight I can see where the water level is about a foot down and I definitely cleaned the drain all the way to the water level. I assumed that past the water level whatever is down there isn't going to find its way into the air in my shower stall but maybe I am wrong?
posted by GleepGlop at 10:23 PM on January 26

It's possible that the water itself is causing the smell, sometimes in Arizona our water gets a distinct moldy/earthy smell that's caused by a natural chemical called geosmin. It's especially strong when you run hot water, and I first noticed it in the shower. We normally get it in late summer, however this link details a problem that Kansas had with it in the winter. I'd suggest asking your neighbors if they've noticed a smell and/or calling whomever provides your water.
posted by TungstenChef at 10:50 PM on January 26

I see in your profile that you're in Ontario, if you're in Toronto the local water department has this page about water taste/smell and gives the following contact info to report problems with water quality:
416-392-2894
or
[e-mail]
posted by TungstenChef at 10:58 PM on January 26

If it's not the drain, then collect water from different sources in your place (the showerhead, the bathtub spigot, the kitchen sink) and see if any of them smell moldy.

I'd also recommend checking the shower curtain. Once the shower's on, there's a lot of water and air going past the curtain, which is one of the places you often find mold.
posted by zippy at 1:44 AM on January 27

Adding to zippy's comment, there was another post on MeFi (that I can't find) that recommended taking separate water samples for the showerhead, spigots, etc, filling several small containers halfway, sealing them, and vigorously shaking for a moment, then smelling.

I used this recommendation personally to find out that a showerhead and line was contaminated somehow. The resulting smell after shaking and inhaling practically knocked me over, so beware- it was a powerful acrid mold smell. This was a guest bathroom that had not been used for over a year.

After buying a replacement head and hose, all was well again. Through the winter, the tub has been home to 4 happy water turtles, and as sensitive as they are, we were fortunate to detect the problem before exposing them to it.

In our case, we only noticed the smell when running the showerhead, and as we were spraying the walls each time in preparation for the turtles, we were positive it was some debris or solvent or something left over from construction that we couldn't scrub off.

Smart of you to consider the red herring, they're everywhere and breed like rabbits. Wet, scaly rabbits.
posted by FrotzOzmoo at 7:00 AM on January 27

There's some good stuff to go on here, I'm going to set to work on this, thanks!
posted by GleepGlop at 2:09 PM on January 27

I´ve found that increasing the humidity in a room for a short period of time can sometimes cause a moldy smell to emerge. Maybe something outside of the shower is emitting this smell when it gets damp from the humidity.
posted by yohko at 8:23 AM on January 28