leak. see pic. the horiz drain pipe going into the wall after the trap in the bathroom is corroded on the bottom. It is corroded on the bottom and all the way thru the pipe up until about 1" from the wall. Closer to the wall, it is still corroded and fells thin on the bottom. It is only a matter of time before it corrodes thru. It is always wet in there. maybe kitchen sink draining water splashes past the common vertical drain pipe and gets the bath horiz wall pipe wet? I dont know and i dont want to call a plumber. Ive owned this house built in 1954 since 1986. This looks like original plumbing. I have done almost all my own plumbing repairs. This one too I have fixed, but it is a temporary patch and Im looking to get ideas how to permanently fix this w/o going into the wall.