The black 90°bend drain plumbing is probably pressing against the small black elbow behind it, keeping the locking collar from locking into place.
Loosen the larger pipe, and then wiggle the elbow while pushing it in and pulling it back.
Leak (circled) at this T near the water heater. It looks like the white collar on the right (compared to the one on the left) is pushed in too far and not sealing. Is that correct? How do I get it to seal?
