2airishuman
Contributor
The elbow that the PVC is attached to also seems to be a standard dimension elbow.
It's not.
I tried to use a standard one from DGX to replace the pull dump the previous owner of my wing had installed. Elbow wouldn't seal. Sanded it down with a pad sander. Still wouldn't seal. Sent it to Tobin. Tobin said some idiot put on the wrong elbow, then sent it back with a new elbow and charged me $20 or something.
BC fittings vary. In the immortal words of Dr. Andrew S. Tanenbaum, "The good thing about standards is that there are so many to choose from."