Got a leaking drain at the back end of the P-trap.
When I pulled the PVC trap apart, there was no washer. Also, the male 90 pipe has flanges that keep the metal nut on the pipe. Haven't seen this type of joint before. Those flanges will defeat the standard PVC joint washer.
How can I stop this leak?
Here are 4 photos of the drain setup with a close up of the strange 90 & its nut & flanges.
Kitchen Drain From Disposer
P Trap
Loosened Nut At Back Of P Trap – No Washer
Male 90 That Slips Into Back Of P-Trap
Best Answer
The typical mid-trap joint of a plastic P-trap does not have a washer. Instead there is a tapered end that fits down into a smooth beveled hole on the opposite piece. The tightening of the nut forces them together to form a tight seal. Your's looks to be this type.
If this joint is leaking for you then there are several probable causes.
It may be possible to stop the leak by a thorough cleaning of the parts. If it is a damaged part then the simplest fix may be to purchase a new set of trap pipe, nuts and washers and just replace the thing. These parts are not at all expensive.