Information seems vague or non-existent from pump manufacturers. I need to know what size pressure tank is required for my setup, and all I'm getting is "doesn't need much" or "x gallons" and nothing about draw down.
I have a 38ft deep well and the submersible will sit at about 35ft deep. I will be pumping 30-40gpm at max demand (when irrigation is on etc.). We are going with a 230v, 3 phase, 2 Horse Power Pump. PVC drop pipe (2") and 200ft of 1 & 1/2", 200lb poly pipe to the house where the controller and pressure tank(s) will live.
A local supplier says a single 7 gallon tank is fine. Another says get 2x7 and the a 3rd supplier says 2x5. No one seems to know why they hold those opinions.
Shouldn't I have enough draw down for my pump to spin up (assuming it takes it a second or two?) and keep a constant 35gpm and 40-50psi? How do I know how much time it will take the pump to catch up to demand? Now, I don't even care about not enough flow to instantly run the entire irrigation system. It's more, do I have enough to:
a. Not damage my pump or pipes or appliances (this is #1 consideration!)
b. Not be annoying if I turn the shower on (not having enough pressure for a minute)
NOTE: I do NOT need advise static water level, water rights/local laws etc. I can legally pump 35gpm and my well could handle 100gpm or more all year round.