Well pumps · overview

Residential well pump basics: what homeowners should know

A house well is a system, not just a pump in a hole. Understanding the pieces — and the three numbers that drive selection — helps you talk to a contractor and read the rest of this section without getting lost in horsepower labels.

What a typical residential well system includes

Most private-well homes share the same building blocks:

• Well — drilled (or sometimes driven) casing, screen or open hole, and a water column that rises and falls with pumping.
• Pump — usually a submersible hung on drop pipe; sometimes a jet pump at the surface for shallow work.
• Drop pipe and check valve — carry water up; a check valve (in the pump or on the line) keeps the column from draining back.
• Pressure control — either a pressure switch plus a conventional pressure tank (on/off cycling in a band), or a constant-pressure controller (often with a small tank) that varies pump speed.
• House plumbing — everything after the pressure tank / sensor: filters, softener, fixtures.

Softeners and iron filters sit after the well can deliver flow and pressure. See the hard water section once the well side is stable.

Submersible vs jet / shallow

• Submersible — motor and pump in the well, under water. Common for deeper residential wells and for many modern 3" and 4" installs. Cooler running, quieter at the house, and the usual choice when the water level is well below the surface.
• Jet / shallow — pump at the surface (or pitless-adjacent), priming and suction (or a jet pack) pull or push water. Often used on shallow wells or when pulling a submersible is impractical. Depth and suction limits matter; they are not a drop-in substitute for a deep submersible duty.

This site’s product-family pages focus on residential submersibles (Grundfos SQ / SQE / SP / SQFlex). If your setup is a jet system, bring that fact to your contractor — sizing language still applies, but the hardware path differs.

GPM, pressure, and total dynamic head

Horsepower is a label, not a size. Three ideas matter more:

• GPM (gallons per minute) — how much flow you need at peak (showers + laundry + irrigation, etc.).
• Pressure (PSI) — what you want at the house gauge for comfortable fixtures.
• Total dynamic head (TDH) — the “work” the pump must do: lift from the pumping water level, pipe friction, and the pressure you want (PSI converts to feet of head), plus any elevation after the wellhead.

A curve must meet your duty point in GPM and TDH. Steadier “city-like” pressure (SQE + CU) still needs that duty covered — the controller does not erase head. Method detail: Sizing by GPM and total head.

Constant pressure vs traditional tank cycling

• Traditional — pressure switch and a sizable tank. Pump runs full-on between cut-in and cut-out (for example 40–60 psi). Simple and familiar; pressure swings are normal.
• Constant pressure — variable-speed pump (e.g. SQE) with a controller and sensor, often a small tank. Speed tracks demand to hold a setpoint.

Neither is “better” for every house. Choose based on how much pressure swing you will accept, casing size, budget, and service support. See SQ vs SQE (constant pressure / CU).

Well diameter and which pumps fit

Casing inside diameter limits which pump bodies clear. Many older or restricted wells need a slim 3"-class pump; wider 4"+ casings open conventional SP-style options with different flow/head envelopes.

• 3" SQ / SQE family — common when diameter is tight and you want soft start and built-in motor protection.
• SP series — often considered when casing allows and the duty wants a conventional SP curve / service path.
• SQFlex — same general “small diameter submersible” idea, but energy input may be solar / hybrid rather than only grid — different system design.

Never force a pump that does not clear the casing with proper clearances. Confirm diameter and setting depth before shopping. Compare families: SP vs SQ / SQE · SQFlex solar / remote · SQ / SQE family overview.

Power, dry-run, and low-yield wells

• Power — most U.S. homes are single-phase. Voltage (often 230 V vs 115 V) must match the pump; cable length and voltage drop matter on deep sets.
• Dry-run / low water — if the well cannot keep up with demand, the pump can run with little or no water and overheat. Protection features help; they do not invent more well yield.
• Low-yield strategies — storage tanks, reduced peak demand, or slower recovery setups are engineering choices — not something a bigger horsepower sticker fixes by itself.

When to call a licensed well contractor

Call a licensed well contractor when you need:

• Pull/replace a pump, set depth changes, or new drop pipe / pitless work
• Curve selection from published manufacturer data against your well log and yield
• Electrical and code-compliant install, including cable and grounding
• Diagnosis of short-cycling, no water, muddy discharge, or suspected dry-run damage

Where to go next

1. Sizing: GPM and total head — method before brand
2. SQ vs SQE (constant pressure / CU) — fixed speed vs steadier pressure
3. SP series vs SQ / SQE — when a conventional SP fits
4. SQFlex solar / remote — off-grid / hybrid energy overview
5. SQ / SQE family overview — broader residential overview

Water quality after the well can deliver: iron · rotten-egg / H₂S · softener sizing by GPG. For optional background reading on well chemistry (not a pump manual), see Well water treatment (book).