Size spa jet flow for smooth hydrotherapy. Enter seats, flow targets, piping details. Get clear recommendations for comfort, efficiency, and balance today.
| Seats | Jets/Seat | GPM/Jet | Design Flow (gpm) | TDH (ft) | Motor Input (hp) |
|---|---|---|---|---|---|
| 4 | 4 | 12 | ~179 | ~32 | ~10.6 |
| 6 | 5 | 10 | ~281 | ~41 | ~21.3 |
| 3 | 6 | 14 | ~251 | ~36 | ~16.6 |
Hydrotherapy quality depends on wet flow delivered at each jet, not just motor size. Start with the jet manufacturer’s recommended GPM per jet, then adjust using the air mix factor to reflect reduced water flow when air is entrained. If design flow is low, jets feel uneven across seats; if too high, noise, turbulence, and control valve sensitivity increase. For multi-seat spas, aim for similar pressure at every seat.
Correct total flow can still feel wrong if distribution is poor. Splitting into multiple branches reduces velocity, stabilizes pressure, and makes balancing easier. The branch suggestion divides design flow into practical segments so each run feeds a similar jet count. Keep branch lengths similar and use gentle sweeps to minimize local losses and minimizes unwanted vibration.
Friction rises sharply with flow, so pipe diameter is a major control knob. The calculator uses Hazen–Williams with an equivalent length that should include straight pipe plus fittings, tees, check valves, and manifolds converted into “feet of pipe.” If fitting counts are unknown, begin with a conservative equivalent length, then refine after the layout is drafted.
Filters, heaters, and restrictive valves add pressure loss at high flow. Enter a realistic equipment loss and the tool converts psi to feet of head and adds static lift and friction to estimate TDH. Reducing restrictions can lower TDH, improve comfort, and reduce electrical demand at the same jet feel.
Use design flow and TDH as a point on the pump curve, then choose a pump that meets that point near its efficient operating region. Confirm suction velocity targets, verify that jet bodies and air lines match the plan, and expect final tuning with diverters and balancing valves after startup testing. Document settings so seasonal maintenance restores the same performance baseline.
Use the jet manufacturer’s wet flow rating at the intended nozzle and valve setting. If unknown, start within 8–16 gpm for many therapy jets and refine after selecting a specific jet model.
Air induction changes the mixture density and can reduce the actual water moved through the jet body. The air mix factor lets you model that reduction while still reflecting the stronger “feel” created by aeration.
Add straight pipe length and convert fittings to equivalent feet of pipe using typical tables. If you are early in design, use a conservative allowance and tighten it once the plumbing layout is finalized.
Increase pipe diameter, shorten runs, reduce restrictions, or split flow across more branches. Lower velocity typically reduces noise, improves balance, and cuts friction head, which can reduce required pump power.
No. It is a planning estimate based on flow, head, and assumed efficiencies. Final selection should be based on the pump curve at the operating point and verified against real equipment losses and plumbing details.
Plot the design flow and TDH on candidate pump curves and choose a model that meets the point near its efficient region. Then confirm suction conditions, jet specifications, and perform startup balancing with valves.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.