Well pump

Short definition

A well pump moves water from a private well bore up to the building’s pressure tank. Two main types: submersible pumps run downhole inside a sealed stainless can, hanging on the drop pipe (standard for any drilled well over about 25 feet); jet pumps sit at the surface and pull water through a suction line (shallow wells under 25 feet, or convertible deep-jet for moderate depths). The pressure tank holds the buffer; the pressure switch tells the pump when to run.

What it is

Three components working together:

• The pump itself. Either a submersible (downhole) or a jet pump (surface).
• The pressure tank. A bladder-type tank pre-charged with air. Water fills against the bladder and stays at pressure between pump cycles.
• The pressure switch. Mounted on the pressure tank or its plumbing, the switch starts the pump at cut-in pressure (commonly 30 or 40 psi) and stops it at cut-out (commonly 50 or 60 psi). Standard pairs are 30/50 or 40/60.

Submersible pumps are multi-stage centrifugal pumps driven by a sealed downhole motor. The pump body and motor (typically 4 inches in diameter, fitting inside a 6-inch well casing) hang from the wellhead on a drop pipe — usually PVC or galvanized — at a depth that puts the intake 10–30 feet above the well bottom. Wiring runs alongside the drop pipe. Modern WA single-family wells run 1/2 HP to 1 HP submersibles on 240V.

Jet pumps sit at the surface (in a well house, basement, or pump shed) and create suction through a venturi.

• Shallow-well jet pulls water directly through a single suction pipe; physics caps the lift at about 25 feet.
• Deep-well jet sends pressurized water back down a return line to drive a downhole ejector (jet body) that lifts water through the suction pipe. Works to depths around 100 feet but is less efficient than a submersible.

For wells deeper than 25 feet, a submersible is almost always the right choice — better efficiency, less noise above ground, fewer prime issues.

Why it matters to a homeowner

Three places homeowner attention pays off:

• Recognize short-cycling fast. A waterlogged pressure tank (bladder failed) makes the pump click on and off every few seconds during use. Short-cycling burns out pump motors. The fix is a pressure-tank replacement, not a pump replacement — but if you ignore it, you’ll need both. See accumulator bladder.
• Know your pressure switch settings. “Low water pressure throughout the house” can mean the pump’s worn, the well’s dropping, or the pressure switch is set too low. Test by watching the gauge: if it reads 50/60 psi cycle but pressure feels low, it’s a fixture or pipe issue. If it reads 20/30 psi, the switch needs adjustment or replacement.
• Don’t run dry. A pump pulling air for any sustained period overheats and burns out the motor. If you draw the well down faster than it recovers, you need a longer drop pipe (lower pump position) or a low-water cutoff control.

When the pump is in the well, you can’t see it fail; you only see the symptom. The diagnostic flow chart for “no water” almost always lives at the pressure tank — gauge reading, pressure switch contacts, control box (for 3-wire submersible), then breaker.

When you’ll encounter this term

• No water at any fixture in the house — pump didn’t run, or ran dry
• Constant short-cycling click from the basement / pump shed
• Pressure-tank gauge reads 0 psi
• Sediment or sand in the water
• Pre-purchase inspection on a rural property — well-pump test included
• Replacing a 25+ year old pump as preventive maintenance

Common variants and not the same as

• Submersible vs. jet pump. Submersible is downhole, more efficient, quieter, standard above 25-foot depth. Jet pump is at the surface, easier to service, limited to shallow wells (single-line) or moderate depth (deep-jet).
• 2-wire submersible vs. 3-wire submersible. 2-wire has the start capacitor inside the downhole motor; 3-wire keeps the start capacitor in a surface control box. 3-wire is more reliable and easier to service.
• Well pump vs. booster pump. Well pump moves water from well to pressure tank. Booster pump pressurizes water already in the building piping for fixtures with insufficient supply pressure.
• Constant-pressure (variable-speed) submersible vs. standard cycling submersible. Constant-pressure systems use a variable-frequency drive to maintain steady pressure (no cut-in / cut-out cycling); standard pumps cycle on/off against the pressure tank.

Common failure modes

• Pump won’t start. Pressure switch contacts pitted or stuck open; control box failed (3-wire); tripped breaker; blown start capacitor (jet pump).
• Pump runs but no water. Loss of prime (jet); broken or split drop pipe; failed check valve; well drawdown below pump intake.
• Short-cycling. Waterlogged pressure tank — bladder failed, pump can’t build pressure between cycles. Replace the tank.
• Sand or silt in water. Pump set too low (drawing sediment from well bottom); failed casing screen; mineral cementation breaking loose.
• Low pressure throughout house. Worn pump (impellers eroded); pressure-switch settings drifted; well drawdown reducing supply.
• Pump trips overload. Motor damaged from running dry; bearing failure; clogged impeller.

Cost ranges (WA, 2026)

Deeper wells, larger pumps, and difficult well-house access push toward the upper end. A submersible pull involves removing the well cap, lifting the entire drop pipe + pump assembly, and resetting it — billable at trip + labor + parts.

DIY scope

• Pressure switch replacement. Moderate DIY. Shut off pump breaker, drain pressure to zero, swap switch, set cut-in/cut-out, restore power, check operation.
• Pressure tank replacement. Moderate DIY. Drain system, disconnect tank, set new tank, pre-charge to cut-in minus 2 psi, plumb in, restore.
• Pulling a submersible pump. Pro work in most cases. Requires equipment (well-pump puller / hoist), space, and the ability to handle 100–500 feet of drop pipe safely.
• Jet-pump priming, capacitor swap. DIY-friendly.

Washington note

WA private wells are regulated by WA Department of Ecology for water rights and WA DOH for water quality. Well construction (drilling, casing, sealing, pump installation) must be performed by a licensed well driller under WAC 173-160. A homeowner can do their own pump replacement on an existing well; new well construction or significant well modification requires the licensed driller.

WA wells split geographically. Western WA wells tend to be shallower (50–150 feet, sometimes shallower in alluvial valleys), drawing from glacial outwash or near-surface aquifers. Eastern WA wells are deeper (200–600 feet, sometimes over 1,000) into Columbia Basin basalt aquifers, with the Spokane Valley-Rathdrum aquifer as the regional standout. Pump sizing follows depth: shallow Western WA wells often work fine with a 1/2 HP submersible or jet; deep Eastern WA wells typically need 1 HP or larger submersibles staged across many pump stages to lift water that far.

If you have a private well, two annual habits keep the system reliable: a coliform test on the well water (DOH’s recommendation) and a visual check of the well cap, casing, and any pump-house plumbing for obvious wear.