My house is 10 years old, with a downstairs bathroom that has a sink and a toilet. Recently, there has been a strong, musty smell in this bathroom that comes and goes throughout the day. It seems to be coming from the sink--but I haven't been able to determine whether the source of the odor is the drain or the faucet. I dumped a half gallon of white vinegar down the drain, which didn't seem improve anything. I also used some Drano kitchen crystals. This seemed to improve things for a couple of days, but now the smell is back and stronger than ever. Any suggestions relating to this matter would be greatly appreciated.

I took this from a post that Speedball (plumbing expert and site moderator) had posted earlier....try this and let us know if it helps.

"Remove the stopper from your lavatory. Look down in the drain and you will see a rod about 6" down. Hair hangs up and fermemts on that rod. Fish it out,(ugh!) Now pour a quart of bleach down the drain and let it set overnight. Next morning,(and this is important)flush it out with a pan of boiling water If you can't pull the stopper out then your stopper has a opening at the base that the rod goes through so that it can't be pulled out. To defeat this and pull the stopper look under the sink and follow the pop up lever down to the rod. You will see a knurled nut. Now push the pop up knob so the stopper is in the up position. While holding the stopper in one hand, slowly back the nut out until it's clear,(You may need to free it with a pair of pliers) Careful! You don't want to pull it all the way out. Now, GENTLY pull back on the rod while pulling upwards on the stopper. As soon as the stopper clears turn the nut back in hand tight or tight enough to hold the plunger rod up. From here on in you will let the stopper ride on top of the rod instead of tying it down. Now take a bent coathanger and fish out any hair that may have hung up on the rod or the trap. After you have cleared out any hair or trash, just drop the stopper back in the drain. When I install a lavatory I never tie down the stopper so that the owner can check the drain without the expense of a service call That should take care of that smelly lavatory. More questions? I'm as close as a click. Good luck TOM" (speedball1)

Thank you very much for the suggestions--I really appreciate it! I was able to check for the hair-- I didn't find any--and also poured the bleach down the drain. Unfortunately the smell is persisting and is now permeating the entire downstairs. I think possibly that the smell is coming from the overflow drain. I am so frustrated that this problem not only exists, but is also so difficult to diagnose--the bathroom is barely used and the sink is only used to wash our hands. I am now going to try the bleach on the overflow drain.

Recently I moved into a mobile home that has the same strong musty smell coming from one of the bathrooms. I have used bleach, amonia, and tsp in the drains, the overflow, the toilet, and in the bathtub. I thought it might be coming from under the sink so I cleaned with tsp and then painted with kilz. For a short time, (a few hours to overnight) the chemicals help but then it's back and can permeat the entire house. Frustrating! Still looking for an answer.