I replaced my plugged AC condensate P-trap with a P-trap that has an internally threaded cleanout plug at the bottom of the trap. Unfortunately, this P-trap has a very small drip in the vicinity of the cleanout plug that does not appear to be due to condensate build-up on the outside of the P-trap. The AC evaporator/condensor is located in my attic, so any leakage will damage the ceiling below. Since the P-trap has been in service about 24 hours, it is filled with condensate and will have to be drained through the cleanout connection, but the P-trap fitting can not be removed for servicing because it is glued into the AC condensate drainage system. In researching the best remedy for stopping the leak, I came across Oatey's Great White Joint Compound with PTFE (White Paste) or Harvey's Wet Set PVC Cement. According to the instructions, the Wet Set PVC cement can be applied to wet fittings, but obviously the cleanout plug will no longer be removable for servicing if this option is pursued. The Joint Compound instructions state that it is flexible, non-hardening, and withstands up to 10,000 psi on fittings, so the cleanout plug can be removed for servicing in the event of future P-trap pluggage; however, there is no mention of whether it can be applied to a wet PVC fitting. Does anyone know if the joint compound would work acceptably on a wet schedule 40 PVC fitting? One thought would be to apply the joint compound to the interior threads of the P-trap cleanout, and then, if the cleanout fitting still has a minor leak, to seal the outside of the cleanout fitting with Wet Set PVC cement. The P-trap is not under any external pressure - just gravity flow of AC condensate from about 12 inches above, which is less than 1/2 psi of pressure. Any suggestions would be greatly appreciated.