Material for diaphragm

[The Ogre]

I'm makin a cannon its built but I'm havin trouble makeing a diaphragm for it,
the valve type is more or less a super enlarged orbit watermaster 57101 valve

here is the main style of the valve it is buit off a 4" Genvoa test T w/ a 2" barrel
I just dont know that to use for the diaphragm, any suggestions?

[iamthewalrus]

just cut out a dist from some rubber, u can buy sheets of it at hardware stores. or some ppl use rubber drain plugs

[spudshot]

if you're using a test tee, i believe they're very thin or DWV, either way, its not very safe at all, only use parts labeled NSF-PW. also i dont like genova's fittings and pipe, they're very low quality compared to other brands, and the pipe wall thickness differs in places, making it possibly weak in some places