Pumps, Water Systems and Testing
The Pumps, Water Systems and Testing domain covers what happens after the hole is finished: pump selection and setting depth, the pressure system, disinfection, and the laboratory work that proves the water is safe.
Pumps and setting depth
- A 4-in. submersible in a 5- or 6-in. well; jet pumps for shallow or large-diameter situations; VFD or constant-pressure controls where steady pressure is wanted.
- Set the pump above the screen and at least 5-10 ft off the bottom, with enough submergence to avoid vortexing at the lowest expected pumping level.
- Check valve at the pump, torque arrestor on the motor lead, cable sized for voltage drop over the full run.
Pressure system
A 40/60 pressure switch with tank precharge 2 psi below cut-in (38 psi). Drawdown should cover at least one minute of pump output so the motor does not short-cycle; a relief valve and backflow protection belong on every system.
Disinfection and testing
New and repaired wells are shock-chlorinated (roughly 100 mg/L free chlorine), left to stand, then flushed until chlorine is gone before the bacteriological sample is drawn. Standard private-well panel: total coliform and E. coli, nitrate, arsenic, plus iron, manganese, hardness and fluoride; Connecticut bedrock wells also warrant uranium and radon consideration.
Worked example
A 12 gpm pump needs at least 12 gal of drawdown for a one-minute run time. At a 40/60 setting a bladder tank gives up about 25-30% of nominal volume as drawdown, so 12 / 0.28 is about 43 gal: select a 44-gal tank, not the 20-gal one on the truck. The 20-gal tank would deliver only about 5.6 gal, cycling the motor roughly every 28 seconds, which shortens motor and switch life.
Traps that cost marks
- Precharge set at cut-in pressure, which cuts drawdown sharply.
- Sampling from a softened, filtered or still-chlorinated tap.
- Setting the pump inside the screen.
- Sizing cable by ampacity alone and ignoring voltage drop on a long run.