We did a roof on the 12th and middle of last week the h/o calls me and says it's leaking. So after work me and my lead go check it out, get in the attic everything and can't figure out where the water is coming from. The thing about it is its showing up on the 1st floor not the second. Pretty much every room in the house has some sort of water damage. So tracking where the water is coming from isn't that easy. On my first visit I cut out the ceiling and found all the plumbing for the shower on the second story ( a vent stack is right there to). So I cut the trap out and replaced it. That was Thursday Friday we had bad rain and nothing, I get a call from him Saturday saying he has water on the floor, so I go over and go on the roof take the pipe boot off the stack, pull like 10 shingles off ice and water it, Karnak it, pipe boot , shingle it and flex seal it. It rained really good last night and he said it's leaking again, Wtf! According to him or was a quarter size puddle in the morning (i have never seen more then a dry pot on the floor under it). The stack reduces from 3" to 1.5" somewhere in the wall on the second floor. Is it posible enough rain could go in the stack, and a leak where ever it reduces. Any other ideas? I don't want to go cutting holes in all his walls. As far as the roof is concerned I'm 100% positive it's not leaking.