Pumps, Water Systems, and Controls
Pumps, Water Systems, and Controls
This domain tests pump selection, setting depth, pressure control, and system protection. Common pump types are submersible, jet, and centrifugal. Submersibles dominate drilled wells; jet pumps suit shallow or special cases. The pressure tank, pressure switch, check valve, and torque arrestor are part of the system, not accessories. The exam expects you to set the pump so it stays submerged, match capacity to well yield, and avoid cycling.
Core rules
- Setting depth: keep the intake above the bottom and below the pumping water level by the required submergence; account for drawdown and seasonal decline.
- Pressure switch: a 30/50 switch cuts in at 30 psi and out at 50 psi; a bladder tank precharge is typically 2 psi below cut-in.
- Pressure loss: elevation adds 0.433 psi per foot; a switch setting at the tank is not the pressure at an upstairs fixture.
- Protection: low-water cutoff, check valve, lightning/surge protection, and properly sized wire.
Worked example
A pressure switch is set 30/50 at the tank, and a second-floor fixture is 20 ft above the switch. Elevation loss = 20 × 0.433 = 8.7 psi. At cut-in, the fixture sees about 30 − 8.7 = 21.3 psi; at cut-out, about 41.3 psi. If the homeowner wants at least 25 psi upstairs at cut-in, raise the switch settings or reduce elevation loss. The reasoning separates tank pressure from delivered pressure.
Traps
- Setting the pump above the anticipated pumping level, causing cavitation and motor overheating.
- Ignoring elevation loss when diagnosing low pressure upstairs.
- Over-sizing the pump so it cycles rapidly or draws the well down below the intake.
- Forgetting the tank precharge; a waterlogged tank causes short cycling.