The center plug is the fill. Right one has the pressure release brarings in it. What is the one on the left. There is whst looks like a flat head in it.hopefully i can get this thing working. It was my grandfathets
"Right" and "Left" is sort of ambiguous, the way the photo is presented, but generally, there should be an overload valve, a fill port, and a working valve which should have two balls. Elsewhere, there should be a release assembly/valve.
