Praher Plastics 150-052 1-1/2" Single Union Blocked Ball Valve SKT/MIP. Praher's unique pinned true single union ball valve design provides for: user friendly handle operation - union nut load does not transfer onto ball seat, thereby providing user with easy handle operation even if valve not operated for a long period of time. "below grade - blocked seat flooded suction design" - valve seat will not blow out from static pressure if union nit is removed.