SpudFiles

I know how to build it, but it would be very nice to understand how it works.

Are you talking about the piston valve? It is just the piston. I left the housing up to the builder.

Piston Valves Explained Visually is the best thread on how they work.

Look in the wiki. There is a section on piston valves.

The piston works like every other piston, but it has a built in check valve so that when the piston fires, minimal air can escape back out the pilot valve (therby forcing it through the barrel). Basically, on the inside of the coupling, there is a rubber washer that is flat against several small holes. Air can go through one way because the pressure behind the piston pushes away the rubber washer, but when firing, pressure from the other side pushes the rubber and forces it to seal the holes.

Wait, so the diagram on the wiki is just the piston? Is it barrel seal or chamber seal?

Well, how could you know how to build it if you don't even know what the piston is?

FYI: it is just the piston as said by Hubb in an earlier response.

I got it now, all i need to know is what size T joint to use

Hubb's piston is designed for use in 2" piston valves.

OK, thanks