Hi all! Need some help here on a water system. Here's my setup. (3) 55 gal barrels, 12volt pump, 30 something gallon pressure tank, on demand propane water heater, shower and kitchen sink only. Everything is working but the shurflo pump won't build pressure. It's old so i sported for a new pump. Ended up with a Remco 3200 rv series pump. 3.2 gpm. Works great, or so i thought. Long story short is when the pressure drops down to 20psi (i have an external 20/40 pressure switch) and the pump kicks on, it won't pump. The fine print for the new pump says "pump will only prime if all pressure is relieved from outlet port". If i leave pump off and run the system down to zero pressure and then turn it on, it will pump and fill up the system till the pressure switch turns it off. But it won't pump with the 20psi in the system still. I have a one way valve directly after the pump, pressure tank is charged to 18psi. What am i doing wrong here? There must be a workaround for this. Or should i just return the pump and get a different one? Please help. Thanks.