9 components coveredField manual · Sump / Well Pump
Goulds JS+ / JRS and Red Lion RJS PREM shallow-well jet pumps: quick sheet
Covers: Goulds JS+ shallow-well jet pumps J5S, J5SH, J7S, J10S, J15S; Goulds JRS shallow-well jet pumps JRS5, JRS5H, JRS7, JRS10; Red Lion RJS-50-PREM (602206), RJS-75-PREM (602207), RJS-100-PREM (602208). Goulds J5/J7/J10/J15 without the S are J+ convertible models (shallow or deep with an ejector) and are only covered here for the shared jet-pump checks. Search terms: Goulds J10S, JRS10, Red Lion RJS-100, shallow well jet pump won't prime, jet pump short cycling, 30/50 pressure switch.
Above-ground centrifugal pumps with the jet (nozzle and venturi) built into the casing, so a single suction pipe runs down the well or to the water source. Both brands are rated for a total suction lift of about 25 ft and ship with a 30/50 psi pressure switch. They must be primed (casing and suction pipe full of water) before they run, and almost every call comes down to air in the suction side, the pressure tank, or the switch.
Safety first
- 120/240 V motor and live pressure-switch contacts: lock out the breaker before opening the switch cover or the motor end. Live-voltage checks are for qualified techs only.
- Never start a jet pump dry. Prime first; dry running damages the seal, impeller and diffuser within minutes and voids the warranty.
- Relieve system pressure before removing the priming plug or any fitting.
- Check or adjust the pressure tank pre-charge only with the pump off and the water drained to zero pressure.
- Do not raise the switch setting above what the pump and tank are rated for.
How it works
The impeller spins water outward; part of that water is sent back through the built-in jet, where the nozzle and venturi create low pressure that pulls more water up the suction pipe. That is why the suction line must be airtight and the pump full of water: air in the system breaks the vacuum and the pump stops delivering.
Total suction lift is limited to about 25 ft, and that 25 ft includes friction loss in the suction pipe, not just the vertical distance to the water. A foot valve or check valve at the bottom of the suction pipe holds the prime between cycles. Goulds advises against filters on the suction side of a jet pump.
The pressure switch starts the pump when system pressure falls to about 30 psi (cut-in) and stops it at about 50 psi (cut-out). The pressure tank stores water between those points so the pump does not start for every glass of water. The tank's air pre-charge, checked with the pump off and the water drained, is normally set about 2 psi below cut-in (about 28 psi on a 30/50 switch).
Motors are dual voltage (115/230 V). Goulds uses a capacitor-start, 3,500 RPM motor with an automatic-reset overload. Red Lion uses a capacitor motor; its published curves show, for example, the RJS-100-PREM delivering about 23 GPM at 5 ft lift and 30 psi, falling to about 13 GPM at 25 ft lift.
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