Last week the toilet on the first floor clogged and spilled all over the bathroom floor. A little while later, we noticed it had dripped through to the laundry room area of the basement immediately below. Cleaned it up, no problem.

Then, this weekend, we started smelling something down in the laundry room. It's a musty odor that could be either mold or sewage or a dead animal or something. It's really hard for me to tell what it is. It's strongest in the laundry room but we've also started to smell it upstairs in adjacent areas.

We've tried pouring bleach down the laundry sink drain and mopping up with bleach. Didn't seem to fix it.

House background: 60 year old house with a new addition last year. Clogged bathroom and laundry room are in the old part of the house. Laundry room has an old laundry sink that was clogged badly last year but we cleaned out the trap ourselves (mostly paint remnants from renovation and lint from the washer that drains into the sink). There is no open floor drain in the laundry room. There is an old sewer pipe of some sort (about 6 inches diameter) that sticks out of the floor about 1/2 inch and is covered with a rubbery cap.

Also, the bathroom toilet that clogged seems to get clogged more than others in the house.

Any ideas?

Hey Mickey:

Start by checking around your plumbing and see if you can find an AAV (air admittance valve... see pic.) fittting anywhere near or in the laundry room? If so, may be defective and will need to be replaced (just unscrews counterclockwise).

Otherwise... may be a sign that a drain or a vent is beginning to clog. Test this idea by running all the fixtures you can at once... all the while keeping an eye on the lowest fixture in the house (may be this laundry sink... yes.. ).

If sink starts to fill with water, or starts gurgling or burping (how the sewer gasses may be getting into the house) then you have clogged drain or vent and will need to address that!

Check for the AAV and then test the main drain line as presented above.

Let me know what you find...

MARK

I didn't see anything like that down there. But, when I was looking around I jiggled the washer to the side and found the floor drain underneath it. Smell doesn't seem to be coming from there, but it's hard to tell.

So there is a floor drain..

Smell is definitely coming from the floor drain if it has not had water poured down it in awhile.

Traps evaporate pretty quickly this time of year! Even if you are not smelling strong odor now if trap is not wetted regularly then this is the issue... ;)

If so... just need to pour water down the drain once/twice a month to keep the floor drain wet!

Let me know what you think...

Mark

I also noticed that one of our bottles of detergent had been slowly dripping down the back of the washer, pretty much right into or beside the drain. There's a huge amount caked on the back of the washer, like the side of a dripping candle. What should I do if this stuff is built up in there too?

Another note... we've been running dehumidifiers down there thinking that perhaps it was mold. Current humidity on one of the machine's readers says 55. Should we turn them off or keep them on?

55% humidity sounds reasonable to me... but really depends on what you feel is comfortable there.

If soap got down the drain I would start clearing by using really hot water to dissolve anything that might have gotten down the drain.

But major issue is the odor... is the floor drain trap dry.. When toilet is flushed upstairs... and you put your ear NEAR the floor drain... can you hear the flow of water in the drain pipe..

Let me know.