Here is what is puzzling me; I have an upstairs bathroom with a shower with formed base and lead liner, a toilet and a sink, all original from 1966. Every couple of days, I will get about a cup of water leaking from the ceiling below. Then for several days nothing. My schedule is pretty consistent from day to day, so I'd think it would leak a little all the time rather than a gush occasionally. About 6 months ago I found the copper drain pipe from the sink had developed a perforation. I cut that section out and replaced it with plastic and it has been fine since - I think. Has anyone run into a similar intermittent leak problem like this? Thanks in advance.