What are you pumping air with? Typically they seal up at approximately 30psi until they get some time on them, broken in. You can help things along by making sure the sealing surface on the diaphragm is clean, no manufacturing debris or deformities. Welcome to Spudfiles. :D I'm just using a bike pump

I am currently building a compressed air canon and am trying to use a sprinkler valve as a trigger. I understand the how it works when modified by plugging up some holes. I am having trouble sealing the diaphragm. When pumping air the air just seeps out and never builds pressure. I have tried 2 valv...