schmolze

i have a very strange thing going on:

directly underneath the return pipe coming out of the hallway radiator, in the basement ceiling, the floor sheathing is all water stained, and actually has been wet to the touch for weeks. the area of staining and wetness is definitely spreading.

upon close examination of the only fitting there (a standard 90º elbow, then pipe going through a hole in the floor) i can't find any trace of wetness or signs of leakage. the oak floor above is totally dry (but is definitely heaving/rolling up due to water coming from somewhere. the fitting is green and funky looking, which looks like just regular flux "ooze," or something.

i was just about to cut out the 90 and sweat another one on, but it's a lot of work and a very tight spot so thought i'd ask you guys first.
when i bought the house the stains were there, but it's gotten much worse.

i guess it couldn't hurt to sweat another 90 on? maybe there is some sort of pinhole leak on the pipe itself inside the flooring? there's no reason i can see that the pipe would be sweating there. it's always dry when i touch it, both above and below the floor.

what gives?

thanks.