Any plumbers in here?

[RGD.]

Originally Posted by Cyanide

....and the truest answer to my problem has come to light. There is a crack right above where the cleanout branches from the main pipe. That is the most "smoking gun" I have come across yet.

Yep that will do it also. That's ABS pipe and extremely common for it to do that - which is why it's not used anymore. Replace as much of it as you can with PVC.

Have fun -



Ron