We recently moved into a new house and have noticed that there is a musty smell in cabinet under a sink in the bathroom. It's been noticeable for about a month. We've noticed that it's strongest shortly (half hour or so)after we use the water. We've taken everything out of the cabinet and there isn't any moisture. We are living in a cement slab home. Do you have any ideas what might be causing this?

I suggest it is mould, remove the cabinet from the wall and use a mould inhibitor. You might also examine how moisture is getting behind the cabinet

Before you pull the cabinet try removing everything and then place tissue covering every inch of the cabinet floor. If you have a drip it will show. Also wrap tissue around where the drain pipe goes horizontally into the wall, many drips happen there. In the long run paraclete may be right. Once a cabinet has gotten wet you need to kill the mold which starts growing within 36 hours of it getting and staying wet.

Thanks for your suggestions. We have checked and are sure that there aren't any leaks in the pipes that we can get to. We are wondering if we should try going into the wall behind the sink (from underneath the sink where the pipe goes into the wall) to check if there's a leak behind there. We have a big double vanity and are really hoping not to have to take the whole vanity out. Thanks again for your suggestions. We can use all the help we can get on this one.

Before you go digging into walls it might be time to call in professional help. It maybe a pipe in the. Wall has developed a leak but stay with the simple explanations first, Check the wall for dampness and press on it. Check the seal in the sink by filling it with water and observe whether there are drips. A bulge in a wall will indicate moisture and depending what the cabinet is made of swelling in wood will also indicate moisture. I have seen a situation where plumbing work was poorly done and the outlet pipe was not properly sealed allowing odours to rise, a slab is no guarantee pipes are properly jointed. Is it possible that the caulking between the sink and the wall needs replacing and is allowing moisture to get behind the cabinet?

I think you're right and we'll need to get some professional help for this one. Since we have a double vanity with wood backing, the back of the wood cabinet is as far as we can get for now. No indication of moisture there. The pipe is loosely fit into the back of the cabinet, clear opening around and the odor does seem to be coming from the hole. Unfortunately, we may just need to get a plumber in. Thanks again for all of your help. It's nice to have a place like this to ask questions before calling someone in.