This acid spitter was built for my 2005 haunt and is driven by a bicycle pump.  It runs on about 40 psi and the solenoid is triggered by a manual switch for saftey.  I teed in another line so when the prop is submerged in the water it fills up the ram  and when triggered the water is forced out of the ram by the  air and blows it out the nozzel located in the mouth.  The nozzel is copper tubing that has been crimped.  It will shoot water about 30 feet and is located close enough to the road that I can blast cars with it if I want to.  I have had alot of compliments on this build.