Fresh water and the pump
Pump won't run: power or ground. Pump runs but no water: tank, strainer or air. Pump cycles on its own: a leak or a bad check valve.
The short version
- No run: check fuse, switch, then voltage right at the pump with it switched on.
- Runs but no pressure: check tank level, strainer, and that the winterizing valve isn't open.
- Cycles with every tap closed: something's leaking or the pump's check valve is bad.
- Pump chatters while running a tap: often normal on cheap pumps, or a low flow restriction.
On the job
- Switch on, a tap open, listen. Silent: 12V at the pump leads. Runs dry: tank, strainer, inlet air leak, winterize valve.
- Cycles with every tap closed: a leak, a weeping toilet valve, or the check valve (drip at the city inlet with the pump on).
- Pulses: clean the strainer and aerators; set the accumulator air charge about 2 psi below cut-in.
- Gauge at a fixture: 40 to 55 psi. Won't build: pump. Builds and keeps running: pressure switch.
Numbers
- Typical shutoff: ~40–55 psi
- Typical draw: ~4–8 A
- Shurflo 4008: about 3 gpm, cut-off about 55 psi, 7 to 8 A
- Accumulator charge: about 2 psi below cut-in
Shop tip
12V at the pump's positive but no run? Check the ground side before you condemn the pump.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.