What this tool does
Translate an observed start count into starts per hour and compare it with a simplified pressure-tank fill-and-draw cycle.
When to use it
Use after safely observing pressure and start behavior. It helps organize measurements before inspecting the tank, switch, check valve, leaks or controls.
Inputs and supported units
Each labelled field explains the quantity it expects. Unit-system changes convert existing numeric entries once and keep calculations on a single SI internal basis. Supported shared units include L/min and GPM, metres and feet, kPa and psi, millimetres and inches, kW and hp, and °C and °F as relevant.
Calculation or decision method
The refill model is unavailable when demand equals or exceeds pump flow. At zero demand, repeated cycling points away from normal drawdown consumption.
How to interpret the result
Read the primary result with the supporting breakdown and warning. A plausible number is not evidence that every input, operating case or design constraint has been included.
Worked example
Six starts in 20 minutes is 18 starts/hour. With 30 L drawdown, 10 L/min demand and 40 L/min pump flow, modeled off/on times are 3 and 1 minutes, or 15 starts/hour.
Assumptions
Constant demand and pump flow during a cycle, usable drawdown is known, and observed starts are counted consistently.
Limitations
The model does not diagnose bladder failure, switch chatter, air charge, a leaking check valve, variable-speed controls or motor limits.
Sources
- Pentair — Steel Pressure Tanks Owner’s Manual
- U.S. Department of Energy — Pump Systems
- Hydraulic Institute — Pump FAQs