Mold growth in basement under shower. Need suggestions to fix leak and clean up mold
 

I've been going thorough planning to redo my currently unfinished basement and everything has been going pretty well until last week when I noticed a slight bit of moisture in a otherwise very dry area. I looked up to the basement ceiling and saw black mold around the drain line of the shower. Not sure the proper term for this but there is a large 3" nut with a thin washer above it, the washer is between the nut and the shower base. Inside the nut is the 2" ish drain pipe coming down. I ran the shower and went back downstairs and watch it and the water appears to be beading from between the waster and the nut, dripping maybe a drop every 30 seconds. My first instinct was to just tighten the nut by hand so I did about a 1/4 a turn and then it started leaking about 1 drip every 8 - 10 seconds. Looking at the wood around the drain it seems sometimes the drops hit the wood and sometimes they fall to the floor. I have what appears to be black mold from the edge of the hole where the drain is to about 2" around it so less then 1 square foot total. So my question:

- Do I remove the nut and try to find the exact same washer? Can I get a materiel and cut my own washer? I don't have any info on the shower but I do have a circle cutter that I can use to cut something out with.

- Could I just pull the nut off and put plumbers putty around it and screw it back together? I want to do it "the right way" since this area will most likely have a bathroom in the basement and I will end up finishing the ceiling so if I shouldn't do this I won't.

- The basement is dry everywhere else and I have no issues of mold anywhere in the house so I know the only reason it's growing here is the leak. For this issue once the leak is fixed can I just wipe down the wood with a bleach solution and leave it or do I have to try and cut out anything with mold (which will be difficult with the plumbing around it but I think doable with a roto tool or something I can set the depth with). Again its less then a square foot and contained only around the leaking drain.

-Allan

can you post a pic

I'm at work but will post something when I get home. The drain pipe is about 2"d, the hole in the wood is about 4"d. The nut is screwed right to the base of the shower with the washer in between the nut and the shower. So the water that is leaking is beading up between the washer and the nut (could be the washer and the tub...hard to tell) and depending on how it drips it just catches the edge of the wood or hits the floor.

After the plumbing is fixed, then yes you can wipe down with a 10% bleach solution. Get everything thoroughly dry and then coat with a sealer like Kilz.

Here is a pic. You can see both the sub floor, the shower, and the mold. The wood itself is a little "raised" about a inch or two around the opening where it's swollen from water but outside this it still seems solid. It doesn't appear to be supporting the base of the shower as from what I can tell there is about a 1/2" gap between the sub floor and the base of the shower (which also might be a problem....it flexes slightly in the middle).

This is what needed to be done, the washer was against the bottom of the unit and I think that was where it was leaking from. Either way I picked up a Sioux Chief 2" non caulk drain at home depot and put it in. It said to use silicone under the lip between the drain and the inside of the shower but I've read other things that said to use plumbers putty so thats what I did (used putty that is). Huge PITA to pull the pipe down from the bottom and get it into the new since there was almost no play in the drain. In fact it appears it angles UP as it meats the main drain which explains why the water in that drain is always so high. The top of the drain is at least higher then the hi point on the way to the main drain so it should be ok. If I ever have to do this again though I think I may just cut the drain and put a new one in that's angled correctly. I ran cold water in the shower for about 15 - 20 minutes and didn't notice anything leaking, at least not obviously.

Once I finished that I took my cordless drill and a 3/4" spade bit and removed a little more wood from around the drain just to make sure that if it does leak again it will not drip on the subfloor and instead just to the basement floor (or a ceiling if I put one in...still better then the subfloor). Once I made the hole bigger I used a solution of 1/4c bleach and 2 1/2c water in a squirt bottle and coated all the wood and the floor where it was dripping with that. Also used the same solution to wipe down my tools and drill. I forgot a respirator and coughed/sneezed out some black gunk a couple times but I'm sure I'll be fine. It was leaking maybe 1/4 cup of water every 5 minutes in the shower so it was really noticeable before. I'll check it again after showering tonight but I think it's good.

-Allan