I just went away from any argentinian horrendously expensive flap check valves for animal drinking trough. Flap valves here in Southamerica have rubber for sealing which gets hard over time and does not close anymore the water. So I went with an engineering madterpiece from Brazil with an ball valve. The whole thing is from engineering plastic and pure stainless steel. The rod, the clamp and the ball are all from stainless steel. The thing just works way better than any flap check valve. Just go for ball check valves where no rubber is used.
