swimquip bronze push pull valve

[tookie]

Help. I have an old, but until recently, working Swipquip bronze push pull valve. Water was leaking from the top where the piston comes through and I was having trouble with the pressure staying on for the pump. I decided the O rings should be replaced. Pool repairman came. He removed the three screws from the top, but could not get the piston out. He said he knew nothing about these valves. I have tried pulling and turning this piston, but can't get it out. I don't know what is keeping me from removing it. I can't get to where the Orings are located unless I remove the sand filter connections. Any help on how to get it out. Desperate to get the pool cleaned. thank you.

[mr_clean]

are you talking about push/pull backwash piston?
Once you undo three screws some top plates screw off by using pipe wrench, then pull-out.