I did an epoxy repair on a 3 x 1 1/2 tee in a 3 inch vent stack last month. I had a heck of a time with a persistent trickle of condensation running out of the failed joint. I finally had to warm the pipe above the tee up to 220 degrees with the heat gun, then quickly pack in and wrap around the joint with plastic repair epoxy, 2 part stick putty. I removed several sections of drywall before I found the source of the leak. I want a bore-scope camera to simplify this kind of trouble shooting next time.
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