Well & Pumps
Shallow Well Pump: Depth Limits, Sizing and When You Need a Deep Well Pump
One number decides it: how far down your water actually sits. Here's where the shallow-pump ceiling really is, when a submersible becomes mandatory, and what 2-wire vs. 3-wire means for servicing it.
By Tim Parker — Reads the spec sheets and prices the full install
Choosing between a shallow well pump and a deep well pump is not a matter of preference or budget first — it's decided almost entirely by your well's static water level, and past a real physical ceiling, a shallow pump is not an option regardless of how much you'd like it to be.
This page is about that depth decision specifically — for how a pump fails or gets sized once you've picked one, see the well pump guide, or start at the well pump & pressure tank hub for the whole system.
Suction lift physics: why 25 feet is a wall, not a guideline
A shallow well jet pump sits above ground and pulls water up a single pipe — except it doesn't really pull. It lowers pressure at its own inlet, and atmospheric pressure pushing down on the water in the well does the actual work of forcing the column upward. At sea level, that mechanism has a hard theoretical limit near 33 feet, because that's roughly how high atmospheric pressure alone can support a column of water. Friction in the pipe and the risk of cavitation eat into that margin further, which is why the practical, real-world limit lands around 25 feet of static water level — not the total depth of the well, which is the distinction people most often get wrong. Adding horsepower does nothing here: the pump was never the one doing the lifting, so a bigger motor doesn't move the wall.
Past 25 feet: convertible jet, or submersible
Once static water level passes that ceiling, a straight shallow jet pump is off the table, and there are two real routes past it. A convertible (deep well) jet setup keeps the motor above ground but adds an ejector assembly down in the casing on two pipes — one drives water down through a nozzle to create suction at depth, the other carries the combined flow back up. It extends useful range to roughly 110 feet, but it moves meaningfully less water per watt than a submersible at the same depth, because energy is spent moving water down the well before any of it comes back up. A submersible well pump sidesteps the whole suction problem: the sealed motor and its stacked impeller stages sit in the water at the bottom of the casing and push rather than pull, so depth is handled by adding pump stages, not by fighting atmospheric pressure. That's why submersibles have effectively no practical depth ceiling and are the standard choice for anything past shallow-jet range — and, increasingly, the default even on shallower wells, since being underwater keeps the motor cool, quiet, and out of a freezing above-ground space.
| Pump type | Workable depth | How it moves water | Where it sits | Trade-off |
|---|---|---|---|---|
| Shallow well jet pump | To about 25 ft of static water level | Pulls via suction — atmospheric pressure pushes the column up | Above ground, in a basement or well house | Easy to service without a rig; hard depth ceiling |
| Convertible / deep well jet pump | Roughly 25–110 ft | Ejector down the well on two pipes; still an above-ground motor | Above ground, ejector assembly down the casing | Extends jet-pump range past 25 ft, but less efficient per watt |
| Submersible well pump | 25 ft to several hundred feet | Pushes rather than sucks — motor and impeller stages hang in the water | In the water, at the bottom of the casing | No practical depth ceiling; servicing means pulling the whole unit |
Depth bands reflect standard suction-lift physics and published pump-curve conventions, not measurements taken by this site. Your own static water level and required flow set the real answer.
Submersible well pumps: the deep-well default
A submersible pump is a long, narrow cylinder — motor sealed at the bottom, impeller stages stacked above it — hanging on the drop pipe in the water. Because it pushes rather than sucks, it isn't limited by atmosphere the way a jet pump is; more stages simply overcome more head. The trade-off is access: nothing about servicing a submersible happens above ground. Any repair or replacement starts with pulling the entire unit, drop pipe and wire together, back out of the casing — which is real rig work, and regulated in most states.
2-wire vs. 3-wire: what it means for the control box
Submersible pumps come in two wiring configurations, and the difference matters mainly for servicing, not performance. A 2-wire pump has its starting components — the parts that get the motor moving from a dead stop — built directly into the motor housing itself, down in the well. That means fewer above-ground parts, but if a starting component fails, the whole pump typically has to be pulled to address it. A 3-wire pump keeps those starting components — a capacitor and a relay — in a separate control box mounted above ground near the pressure tank. If a start component fails on a 3-wire system, it's often a control-box repair at the surface, no pulling required. That serviceability difference is the main practical reason to prefer one wiring type over the other; it does not by itself change how much water the pump moves.
Common questions
How do I know if I need a shallow or deep well pump?
It comes down to one number: your well's static water level, the distance from the ground to the resting water surface (not the total depth of the well casing, which is a different and usually larger number). Under about 25 feet, a shallow jet pump works. Past that, physics rules it out regardless of horsepower, and you need either a convertible jet setup or, more commonly today, a submersible.
Why can't a shallow well pump go deeper than 25 feet?
A jet pump doesn't pull water up a pipe — it lowers pressure at its inlet and lets atmospheric pressure push the water column up from below. At sea level that has a hard theoretical ceiling near 33 feet, and friction losses plus cavitation margin bring the real-world practical limit down to roughly 25 feet. More horsepower doesn't change the number, because the pump was never doing the pulling in the first place.
What is a submersible well pump?
A long, narrow sealed unit — motor at the bottom, stacked impeller stages above it — that hangs in the water at the bottom of the well casing rather than sitting above ground. Because it pushes water up from below instead of pulling it, depth adds stages rather than hitting a wall, which is why it's the standard answer for anything past shallow-jet range and increasingly the default even for shallower wells.
What's the difference between 2-wire and 3-wire submersible pumps?
A 2-wire submersible has its starting components built into the motor itself, down in the well — simpler above-ground wiring, but the control gear can't be serviced without pulling the pump. A 3-wire submersible keeps the starting capacitor and relay in a separate control box mounted above ground, so a failed start component can be replaced at the surface without pulling anything from the casing. 3-wire setups are generally easier to diagnose and cheaper to service for that reason; 2-wire setups have fewer above-ground parts to fail.
Can I convert a shallow well setup to a submersible?
Yes, and it's a common upgrade when a static water level has dropped over time, or when a shallow jet pump is being replaced anyway. It requires the well casing to physically accommodate a submersible unit and enough clearance for the drop pipe and wire, so it's a job for a licensed well contractor to assess, not a straight parts swap.
Keep going
Already know which pump type you need and want the sizing details? Well pump guide. Chasing short cycling or a pressure problem instead of a depth question? Well pressure tank guide. Want the full system view? Well pump & pressure tank hub.