On Nov 29, 8:55 pm, wrote:
I cannot bust this cleanout cap free to save my life and I'm afraid
that I'm going to strip it with my adjustable wrench or pipe wrench.
Some are square but some are not - this one is not. I'm thinking it's
1 5/16" My biggest socket is 1 1/4 and its a no go.

You're going to break the cap whether you want to or not. Don't waste
time on it. Just drill enough holes around the nut (staying away from
the threads) to take it out in pieces. Then when you install the new
cap, do what the original installer didn't, use teflon tape or a non
hardening pipe dope to make it removable in the future. HTH

Joe