Step 3: Modding The Sprinkler Valve
You should find all the materials at Home Depot.
You'll need a:
1" sprinkler valve
1/4" brass nipple
1/4" blow gun
Take all the screws out of the lid from the sprinkler valve and then pull the lid off. Leave the rubber diaphragm in place and make sure you don't lose the spring.
Get a drill bit that is slightly small in diameter then the brass nipple and drill a perfect hole in the middle of the lid from the sprinkler valve. Put some teflon tape on the brass fitting and thread your blow gun on, make sure to remove the nozzle from the other end if it has one.
Step 3:Thread the blowgun with the brass nipple into the hole, make sure to do it slowly and perfectly straight. Remove the solenoid (big black thingy) from the sprinkler valve. Mix a small amount of epoxy and clog up the hole where you just unthreaded the solenoid from.
That's it, just leave it to dry.
The sprinkler valve will be used as the pilot valve for the piston. You could get away with a 1/2" ball valve instead but this will give you more power. Any problems with the valve, read this: