Wall vacuum port thread size

Mar 10, 2016
44
San Diego
Bought a house, it already had a pool. So It has a port just below the water line. It’s threaded There was a capped off pipe by the equipment. Figured it was connected so we checked and it was.

My buddy who does pools says if I connect it to suction that I need to install a vacuum lock in case it sucks someone’s eyeball out or worse. So I bought a Hayward W400BWHP. It fits sort of, will screw three or four turns and that’s it. It absolutely won’t go in any further.

Is it possible it’s not 1.5” npt or whatever? Maybe calcification or something? Or someone previous cross threaded it? I want to actually use it as a return line now and install a pool skim so I’m hoping to get some sort of thread in there
 
They are all 1.5" NPT. You may want to try chasing the thread or take an old tootbrush and scrub out the threads. Then see if it threads in further. You may have to do this a few times to get the safety cover to thread in fully. Even if it winds up sticking out a bit, it's better than leaving uncovered.
 
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