In short: a shallow well with 20 ft of lift, 10 ft of additional elevation, 5 ft of friction loss and a 40 psi tank target needs about 127.4 ft of total dynamic head — most of it (92.4 ft) just from the desired tank pressure. At 10 GPM and 40% efficiency, that's roughly 0.80 brake horsepower. Use the calculator above for your own well and system.
These figures are planning aids based on standard pump-sizing formulas. Confirm the result against a specific pump's performance curve, and check local well and plumbing codes, before final selection.
How to size a jet pump
A jet pump has to overcome four things at once: the vertical lift from the water source, any further elevation to where the water is used, friction loss in the pipe along the way, and the pressure you want the system to hold — which itself is really just more head in disguise. Add them together and you get the total dynamic head (TDH) the pump has to produce.
This calculator converts every input into a common head, sums them, and converts the total into flow-and-head units, hydraulic power and brake horsepower — the numbers you compare against a manufacturer's jet pump performance curve. For a general TDH calculation not scoped to a jet pump — a submersible well pump or a booster application — see the total dynamic head calculator or the submersible pump size calculator.
Worked example. A shallow well with 20 ft of suction lift, 10 ft of additional elevation to the pressure tank, 5 ft of friction loss, and a 40 psi target: 40 psi converts to about 92.43 ft of head. Add the three head terms: 20 + 10 + 5 + 92.43 ≈ 127.43 ft — exactly what the calculator shows with its default values. At a 10 GPM design flow and 40% efficiency, that works out to about 0.80 brake horsepower.
Shallow-well suction lift is the one hard limit. A single-pipe, above-ground jet pump pulls water up by suction, and suction is fundamentally limited by atmospheric pressure — about 33.9 ft in theory at sea level, and about 25 ft in practice once friction, minor losses and cavitation margin are accounted for. Enter more than that as a shallow well and the calculator flags it: switch to a deep-well (two-pipe) jet pump or a submersible pump instead.
TDH by vertical lift (10 ft elevation, 5 ft friction, 40 psi)
How total dynamic head grows with lift alone, holding elevation, friction and tank pressure at the calculator's defaults. 25 ft is the practical shallow-well suction-lift limit.
| Vertical lift | TDH | BHP |
|---|---|---|
| 0 ft | 107.43 ft | 0.678 |
| 5 ft | 112.43 ft | 0.710 |
| 10 ft | 117.43 ft | 0.741 |
| 15 ft | 122.43 ft | 0.773 |
| 20 ft (default) | 127.43 ft | 0.804 |
| 25 ft (shallow-well limit) | 132.43 ft | 0.836 |
TDH by tank pressure (20 ft lift, 10 ft elevation, 5 ft friction)
Tank pressure alone often accounts for more of the total head than the well lift does — this table isolates its effect.
| Tank pressure | TDH | BHP |
|---|---|---|
| 20 psi | 81.22 ft | 0.513 |
| 30 psi | 104.32 ft | 0.659 |
| 40 psi (default) | 127.43 ft | 0.804 |
| 50 psi | 150.54 ft | 0.950 |
| 60 psi | 173.65 ft | 1.096 |
Worked examples
Typical shallow well
127.4 ft TDH
20 ft lift, 10 ft elevation, 5 ft friction, 40 psi tank target, 10 GPM — the calculator's defaults. About 0.80 brake horsepower at 40% efficiency, well within the 25 ft suction-lift limit.
Shallow well at the suction-lift limit
25 ft lift
Push the same system to 25 ft of lift and TDH rises to about 132.4 ft — still workable, but right at the practical ceiling for a single-pipe shallow-well jet pump.
Deep well, two-pipe jet
202.0 ft TDH
An 80 ft deep well with 10 ft elevation, 8 ft friction, a 45 psi target and 12 GPM needs about 202 ft of TDH and roughly 1.75 brake horsepower at 35% efficiency — well beyond shallow-well suction range, which is exactly what a deep-well jet assembly is built for.
What else affects the result
Altitude. The atmospheric-pressure limit behind shallow-well suction lift drops with elevation — roughly 1 ft less practical lift for every 1,000 ft above sea level. A shallow well that works fine near sea level may need a deep-well pump instead at higher elevation.
Pipe size and length. Undersized or long suction and discharge piping adds friction loss and can starve the jet of the flow it needs to maintain suction — check the friction head loss calculator for your actual pipe run rather than assuming a flat estimate.
Jet and nozzle sizing. A jet pump's ejector assembly — the nozzle and venturi — is matched to a specific flow and lift range by the manufacturer. Two pumps with the same motor horsepower can perform very differently at the same TDH if their jet assemblies are sized for different depths.
Priming. Shallow- and deep-well jet pumps both need to be primed (filled with water) before they can develop suction or ejector flow — losing prime is a common cause of a jet pump that runs but doesn't deliver water.
Frequently asked questions
What's the difference between a shallow well and deep well jet pump?
A shallow-well jet pump uses a single pipe and pulls water up by suction, with the jet (venturi) assembly built into the pump itself above ground — limited to a practical lift of about 25 ft. A deep-well jet pump uses two pipes, with the jet assembly submerged down in the well; pressurized water is pushed down one pipe to the jet, which pushes water up the second pipe, avoiding the suction-lift limit and reaching much greater depths.
How deep can a shallow well jet pump lift water?
About 25 ft in practice, well short of the roughly 33.9 ft theoretical limit set by atmospheric pressure at sea level. The gap exists because friction, minor losses and the need to avoid cavitation near the pump's suction all eat into the theoretical maximum, and that maximum itself drops with altitude — roughly 1 ft less for every 1,000 ft of elevation.
What TDH should I use to size a jet pump?
Add up the vertical lift from the pump (or the submerged jet, for a deep well) to the pumping water level, any additional elevation to the point of use, friction loss in the piping, and the head equivalent of your desired tank or delivery pressure. That total — the total dynamic head — is what the pump has to produce at your design flow rate.
Why is jet pump efficiency lower than other pump types?
The venturi ejector that gives a jet pump its lift works by mixing a high-velocity jet with the incoming water, which is inherently lossy compared to a centrifugal impeller moving water directly. Typical overall jet pump efficiency runs around 30–45%, noticeably lower than a comparable submersible or centrifugal pump.
What if my well is deeper than a jet pump can handle?
Most deep-well jet pumps top out in the range of 90–150 ft depending on the specific jet assembly and pipe sizing. Beyond that, a submersible pump — installed down in the well itself, pushing water up rather than pulling or ejecting it — is the standard choice. See the submersible pump size calculator for that case.
How much does tank pressure add to the required head?
More than most people expect. A common 30/50 psi pressure switch setting averages to about 40 psi, which alone is equivalent to roughly 92 ft of head — often more than the well lift itself. That's why residential jet pump total dynamic head figures commonly run well over 100 ft even for a modest, shallow well.
Sources & references
- Hydraulic Institute. ANSI/HI Pump Standards — total dynamic head and brake power formulas.
- Water Systems Council. Jet Pump Application Guidelines — shallow-well suction-lift limits.
John Mac, PE
Water Systems Specialist · Austin, Texas
Texas-licensed Professional Engineer with 13+ years in residential water systems and 180+ completed projects. Writes and reviews the calculators on watercalculator.us. Read full bio
Texas PE (2016) · BS Civil Engineering, Hydraulics (2013)