Pumps, Water Systems, and Well Development
What the exam tests
Pump and system questions test head calculations, component placement, and development. You need to know why a pump is set where it is and how to prove a well is clean and productive.
Core rules
- Total dynamic head = vertical lift from the pumping water level + pressure head + friction loss. Pressure head in feet = psi × 2.31.
- A submersible pump is set above the bottom, below the pumping level, and above the screen; a pitless adapter carries water through the casing below the frost line and allows service without digging.
- A check valve holds prime and protects the pump from backspin; the pressure tank supplies drawdown and limits cycling; the sanitary seal keeps surface water out of the casing.
- Development continues until the water is clear and sand-free. A pump test measures yield, drawdown, and specific capacity (gpm per foot of drawdown) before the pump setting is finalized.
Worked example
A pump is set at 120 ft, static water is 40 ft, pumping level is 60 ft, cut-out pressure is 60 psi, and friction loss is 10 ft. Use the pumping level, not static: lift = 60 ft; pressure head = 60 × 2.31 = 138.6 ft; TDH = 60 + 138.6 + 10 = 208.6 ft. The reasoning: the pump must lift from the drawn-down level and also overcome the tank pressure and pipe friction.
Traps
Using static water level in the head calculation; forgetting to convert psi to feet; sizing a tank to pump capacity rather than to demand and drawdown; and setting a pump below the screen or into the fill.