TradesHow this works
The pump has to overcome three things at once: the lift from the pumping water level, the pressure you want at the tank, and the friction in the drop pipe and run. This tool adds them into a total dynamic head, converts that and your flow into water horsepower, and recommends a pump size. When friction is a big share of the head, it shows what a larger drop pipe would save.
Use the size and duty point to pick a real pump from the manufacturer curve at your flow and head. On a low-yield well, match the well first so you do not overpump it.
Common questions
What is total dynamic head?
It is everything the pump has to push against: the vertical lift from the water level up to the surface, the pressure head to hold your tank pressure, and the friction loss in the pipe. Add those three and you have the head the pump must deliver at your flow rate.
Why do I convert psi to feet?
Pumps are rated in feet of head, but you want a pressure in psi at the tank. One psi is about 2.31 feet of water column, so 50 psi is about 115 feet the pump has to add on top of the lift and friction.
Can a bigger pump hurt?
On a low-yield well, yes. A pump that moves more than the well recharges will pump it down and draw air, which damages the pump. Size to the well yield first, and never just round the horsepower up for headroom on a marginal well.
Sources: Standard pump hydraulics: TDH = lift + pressure head (2.31 ft/psi) + friction head (Hazen-Williams); water HP = GPM x head / 3960. Engine version 1.0.0. Risk tier 2.