Hi - We have a standard bathtub with tiled walls. There is a small hatch for access from the finished basement centered around the drain plug. We are getting water (several ounces after a shower) through the hatch. BUT - the details are interesting:

a) it happens ONLY after a long steamy shower. Long baths, short showers, & long-not-steamy-showers produce no leak..

b) We hung sheet plastic on the front (plumbing) wall and long-side of the tiled tub area, using shipping tape to attach to curtain, and also to seal along where the tub meets the tile. This had -no- effect. (although the tiled plumbing wall behind the plastic still got damp after a long steamy shower).

c) from below we can see the water appears to be coming from the front-right area (to the right of the spout) - it's possible the source is behind the plumbing wall.

d) There has -always- been a small area of the regular (plastered blueboard) wall to the right of the front of the tub (about 3" wide and the height of the tub) where the paint rots over time. Moisture behind the wall would explain it, but no plumber has been able to explain why this occurs. (Note - we've even had the bathroom torn to the studs and rebuilt once (to replace the tub 15 years ago)).

e) The bathroom is 5' x 8' and has an oversized (200cfm) exhaust fan that always runs during the shower and for a time afterwards. It vents to the attic next to a 3' x 3' gable vent (so essentially to the outdoors).

I'm in New England. It doesn't seem like water from the shower is somehow getting directly through the wall. It rather seems like the steam created by the shower somehow causes moisture to condense and drip behind the wall, but I can't come up with a working model in my head to explain the behavior.

I really want to do all the testing I can, to have a clue what is going on, before I call a plumber.

Any/all ideas much appreciated. Many Thanks!

/j



Edited 2 times.

remove the shower head and cap the chrome nipple.
turn things on to see what happens.

Where are you located. Off the top of my head I would recommend that you not vent steam into your attic no matter how close you are to an outside vent. You are creating a possible mold problem and attic vents are intended to move air through the attic to keep temperature down in the summer mostly.