Short answerIf the water surface is more than about 15 to 20 ft below the pump, you need a submersible: a surface pump cannot pull water higher than that in practice. Surface pumps suit ponds, creeks, springs and tank-to-tank transfers.
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Key takeaways
- Surface pumps can pull water up only about 15 to 20 ft in practice.
- Below that the pump must go in the water: a submersible pushes rather than pulls.
- Diaphragm and helical rotor pumps hold flow at high head; centrifugal pumps suit high flow at low head.
The suction limit
A surface pump lifts water by lowering the pressure in its inlet so the atmosphere pushes water up the suction pipe. At sea level the atmosphere can hold up a column of water about 33.9 ft tall at the very most, and less at altitude. Friction in the suction line, the water's vapour pressure and the pump's own losses eat most of that margin. In practice, keep a surface pump within about 15 to 20 ft of the water surface, and closer at altitude.
Below that, the pump has to be in the water. A submersible pump pushes rather than pulls, so the only limit on depth is the head it can generate.
Side by side
| Submersible | Surface | |
|---|---|---|
| Water source | Drilled well, deep cistern | Pond, creek, spring box, shallow cistern, tank to tank |
| Lift limit | Pump's maximum head (230 to 270 ft for the small DC pumps we list) | About 15 to 20 ft of suction, then its own discharge head |
| Typical solar flow | 1 to 10 gpm | 1 to 20+ gpm at low head |
| Priming | Never needs it | Needs a primed suction line and a foot valve; can lose prime |
| Freezing | Below the frost line in the well | Must be drained or housed |
| Service | Pull the pump and drop pipe | At ground level |
| Common types | Diaphragm, helical rotor, multistage centrifugal | Diaphragm, rotary vane, centrifugal |
Pump types inside the housing
- Diaphragm pumps are positive displacement: each stroke moves a fixed volume. They hold flow well as head rises, run on little power and are the usual choice for 12V and 24V systems. Diaphragms and valves wear and are a routine replacement.
- Helical rotor (progressive cavity) pumps turn a steel rotor in a rubber stator. They handle high head at low flow efficiently and are common on deeper solar wells. Sand wears the stator.
- Centrifugal pumps spin an impeller. Efficient at high flow and low head, which makes them the default for pond circulation, fountains and transfer pumping, but their flow collapses as head rises.
Rules of thumb
- Water more than about 20 ft down: submersible.
- Pond or creek, tank within 30 to 50 ft of rise: surface pump in a ventilated, drained housing, or a floating or bottom-set submersible.
- Silty source: screen the intake well above the bottom and prefer a pump type the merchant rates for some sediment.
VEVOR 12V DC 120W submersible deep well pump
Low-volume wells: a cabin, a garden or a few head of stock. The deepest submersion rating of the three.
- Voltage
- 12V DC (12 to 14.8V)
- Rated power
- 120 W
- Max flow (zero head)
- 3.2 gpm
- Max head (zero flow)
- 230 ft
- Max submersion
- 98.4 ft
- Outlet
- 1/2 in
- In the box
- Pump only: no panel, controller or pipe
VEVOR 24V DC 277W submersible deep well pump
Stock water and small irrigation where the water level is within about 100 ft.
- Voltage
- 24 to 42V DC (36V rated)
- Rated power
- 277 W
- Max flow (zero head)
- 9.25 gpm
- Rated point
- 5.28 gpm at 84 ft
- Max head (zero flow)
- 272 ft
- Max submersion
- 65.6 ft
- Outlet / cable
- 1 in / 33 ft
- In the box
- Pump only
VEVOR 48V DC 369W submersible deep well pump
Deeper lifts at modest flow. Wants two 36V-class panels in series to reach its voltage.
- Voltage
- 48 to 82V DC (72V rated)
- Rated power
- 369 W
- Max flow (zero head)
- 8.4 gpm
- Rated point
- 1.77 gpm at 167 ft
- Max head (zero flow)
- 273 ft
- Max submersion
- 65.6 ft
- Outlet / cable
- 1 in / 33 ft
- In the box
- Pump only
We have not tested these products; specifications are the merchant's own. Affiliate disclosure.
Questions
- Can a surface solar pump draw from a 30 ft well?
- Not reliably. 33.9 ft is the theoretical maximum at sea level with a perfect pump; real pumps manage 15 to 20 ft. Use a submersible.
Three DC well pumps side by side on the merchant's own figures, plus panels, controllers and batteries.