We recently noticed wetness in our utility room next to our furnace and water heater. Today my husband noticed that while the kids were draining the tub on the 2nd floor there was dripping from above in the basement utility room. There is no actual ceiling in the utility room it is just studs, and some of the insulation was wet but not a lot of damage otherwise. The leak is hard to locate because of HVAC stuff. It doesn't seem to leak when the water runs, when there is water sitting in the tub, but only when the tub is draining. We tested the two 2nd floor sinks and saw no dripping. The shower in the 3/4 bath drips a tiny bit after a while but didn't drip like it did with the tub draining. (Not sure if it was due to how much more water flows with the tub, or if some dripping when the shower ran was residual from tub) We are wondering where the best place to start would be to find the leak. The tub is older (1980) but it seems intact and in good condition. We've been in this house for almost 3 years and just started noticing the wetness. It hasn't been going on for too long I think. Again, the dripping occurs when the water drains on the 2nd floor, and is dripping into the basement utility room and no other areas of the house have shown signs of water damage. We can't think of any obvious places to look behind walls since there is no visible wetness on the main floor or anywhere else in the house.