I am working on hobby project with almost no budget. I bought some "nice" (cheap & simple) electronic solenoid valves for water flow. I've since discovered that they need 3PSI to open. Which is ok for the supply lines. But the drain line requires that as well. Now I either need a column of water of 3x27.7" (about 7 ft) or soe other way. The valves have a 1/2" inlet, which I calculate to be .78 sqin. I'm not interested in the flow but I need a way to reduce the required height. I thought about putting a fat section of pipe to increase the water held above it. A 6" PVC pipe has a area of 28", divide this by .78 = 36. Divide the 3PSI height (83") by 36 = 2.3" So a 6x2.3" canister should do it. However, I know that pressure is not linear and weird things happen like velocity increases and pressure drops. What can I do to get the height of the column of water down to less than 12" using my 1/2" valve and gravity?