I have a Weil-McLain Boiler EG natural gas model - steam boiler - residential home. Previous years I would occasionally drain off the "sludge". Now, the drain valve is stuck. When I try to turn it open, the handle turns around, but nothing happens. There is a screw in the middle of the handle and I tried to use a screwdriver to keep it tight while turning the handle, but that does nothing. This is the same when the boiler is on and off and hot or cold. Is it just a stuck washer? Do I need to replace the drain/faucet? Thank you in advance.