there is a flapper inside that only goes in one direction. get a screw driver and gently push on the flapper. the side that moves up or "open" goes on top.
there is a flapper inside that only goes in one direction. get a screw driver and gently push on the flapper. the side that moves up or "open" goes on top.
If you could blow from both sides the flap could be warn out . I would test it with water before installation if I was you, it may save you doing it twice . These are pretty cheap why not replace with a new one if i doubt .