I let the water drain out then i cut out the nut using a metal cut off wheel rotozip.
Drain clean out cap stuck.
Once it s safely removed use the old fitting as a guide to cut a replacement section of pipe and clue up a new.
Open the cap and let the buildup drain out quickly open the cap and step out of the way.
After this i used the cut off wheel to slice away portions of the cap until i could get near the inner.
Https amzn to 354hhrh plumber s pipe wrench.
Remove the cleanout plug with finesse and force photo 1.
Dousing the plug several times with penetrating catalyst lubricant often also called a rust breaker is another way to.
Slide both couplers onto the old pipe then slide the vertical.
Https amzn to 3lszden make your own sewer.
If all your efforts fail you may have to cut out the fitting and install a new one.