SpudFiles

What is the best type of rubber to use for a pistion on a piston valve

Any reasonably thick neoprene sheet will do, take apart a truck inner tube or buy it off eBay

I always buy a 8"x8" sheet of "gasket rubber" from my local hardware store for a couple of bucks. Works for me. It's about 1/8" thick and red in color.

I used a 1/2" thick machinery pad from Mc-Master Carr. Very durable belted rubber. A little hard to work with but worth it!

Any kind of rubber you can get your hands on will work. People have even used mouse pads before, but I dont reccomend that. The cheapest way would be what jhalek90 said. At Lowes, they have 8 X 8 inch sheets of gasket rubber for under two bucks and will work beautifully!! I have yet to get my piston to work right, but this rubber seals my barrel and works for me!! Good luck and let us know how you make out!!

Thanks I was doing some research and polysulfide rubber or silicone rubber any opinions on that

You could also go to a local tire shop and ask if you can cut the sidewall from a car tire. The sidewall is not steel belted, just cords. Not to mention its free, cuts easily with a razor knife, and is virtually indestructable. The "Red" gasket material doesn't last long when you use the piston valve at higher pressures because it is not belted with some sort of fibers. It just smashes apart eventually causing your piston to leak. A tire sidewall is the only other type of sealing face rubber I have experience with and It was good. If you really wanted to you could calculate the area of your piston and figure out how many PSI your rubber choice should be able to withstand if you have something else in mind Cheers!

I found the perfect way to seal off the barrel using a soup can idea unfit from my other question about a piston it's a Tank to bowl gasket for a toilet it fits perfectly around 2" PVC and made a really nice seal for me if anyone else wants to try it out (it will need some trimming to fit in a 3" tee if that's what you are using)