For the past few months we have been noticing a bad, sulfur-type odor coming from our master bath toilet and sink. The smell is not constant and doesn't always correspond to running water (running both hot and cold water in the sink can cause the smell, but it disappears after a few minutes) or flushing the toilet. Sometimes the smell is there in the morning before any water has been used. Also, the smell doesn't come from the tub at all and you can't smell it in the cabinet under the sink. We don't have this problem anywhere else in the house. Any ideas?

I was kind of hoping one of the experts would pick up on this. Smells and noises are the most difficult to track down if you're not there.
While we can't pinpoint the source we can point you to the most likely offenders. Most bad smells from showers and lavatories come from rotting hair matted in with grease in the drain lines. Try this for the smell. Pull the lavatory stopper and look down the drain. About 4 inches down you'll se a small rod sticking out. Fish out any hair that's caught there. Tonight before bedtine Take a gallon of bleach and pour half down the drain and let set over night. Next morning ,(and this is important) flust out the drain with two large pans of boiling water to loosen the grease and flush the mess out.
This should make your drains smell better.
As for the toilet, you might have bacteria growing in there. Try this, take a couple of gallons of bleach and tonight before bed time shut off the water to the toilet and drain and sponge out the tank. Now dip and sponge as much water out of the bowl as possible. Pour a gallon of bleach in the tank and wash down the sides and the underside of the tank lid. Now flush the bleach out and pour the other gallon into the tank and flush it down as well. Brush the sides of the bowl down. This should get any water left in the trap and bowl out leaving the bleach to work. LET IT SET OVERNIGHT! Next morning turn the water back on and flust the bleach out. Good luck, Tom

Thanks for the help! We will give it a try...