Vertical pressure tank connected to a water pump outdoors
4 components covered

Field manual · Sump / Well Pump

Residential well pump systems: field service manual

Covers: Private-well systems with submersible or jet pumps, captive-air pressure tanks, mechanical pressure switches and constant-pressure drives (e.g. Franklin SubDrive/MonoDrive)

Cross-checkedBrands: Goulds, Red Lion, Franklin Electric, Pentair, Wayne, Others4 components

A well pump fills a pressure tank until a pressure switch (or a drive with a transducer) says stop. The tank's air cushion lets the house draw water without restarting the pump every few seconds. Most service calls are tank precharge, pressure switch and electrical issues; anything downhole goes to a licensed well contractor.

Safety first

  • 240 V and high current: breaker off and verify dead before opening switches or drives
  • System under pressure up to about 80 psi: drain before opening plumbing
  • Pulling a submersible pump requires a licensed well contractor

How it works

Submersible pumps sit down in the well casing; jet pumps sit above ground and pull water up, and must stay primed.

A conventional pressure switch starts the pump at the cut-in pressure and stops it at cut-out (common ranges like 30/50 or 40/60).

The captive-air tank has a bladder or diaphragm with an air precharge. Correct precharge is set with the system drained, slightly below cut-in.

Constant-pressure drives vary motor speed to hold a setpoint and report faults on a display (Franklin F-codes).

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Vertical pressure tank connected to a water pump outdoors by W.carter, CC BY-SA 4.0

Diagnostic guides for this appliance

Guide · Sump / Well Pump

Sump pump trips the GFCI or breaker

A GFCI that trips with a sump pump is usually detecting real current leakage from a pump motor taking on water, a damaged cord or splice, or another load on the same circuit. Isolate the pump from the circuit before blaming the GFCI, and never bypass the protection on a pump in water.

4 steps ~45 minmoderate
Guide · Sump / Well Pump

Sewer or musty smell from the sump pit

A clean sump pit should not smell like sewage. Most odors come from a pit that has dried out and no longer seals the drain tile lines, stagnant water, organic buildup, or nearby plumbing traps that have dried or been siphoned. A strong, persistent sewage smell can mean a leaking sewer line near the pit.

6 steps ~30 mineasy
Guide · Sump / Well Pump

Sump pump keeps cycling when it has not rained

The most common cause is water returning from the discharge pipe through a failed or missing check valve, so the pump moves the same water again and again. Other causes are a small basin, a float set too close, a high water table or a leak feeding the pit.

4 steps ~40 mineasy

Other sump & well pumps manuals

Manual · Sump / Well Pump

Residential sump pump systems: field service manual

120 V residential submersible and pedestal sump pumps, float switches, check valves, discharge piping and DC battery backup systems

4 components4 common failuresZoeller, Wayne, Liberty, Superior Pump, Basement Watchdog, Little Giant, Pentair
Residential well pump systems: field service manual · OnCall Tech