Re: [VAL] Neat ABS fitting

[Gerald <geraldj@xxxxxxxxxxx>]

Sounds to me as if its an expansion piece. Just should slide apart.
Allows the vent and the tank to move independently without breaking any
connections. Needed in long drain runs to account for thermal expansion
in plastic. I don't find any in either Home Depot or McMaster-Carr.
Likely the o-ring has worn a groove to make it hard to separate.

Gerald J.