Pool TDH & Pump Comparison Calculator
Estimate pool total dynamic head and compare pump performance at the resulting system resistance. Use pressure and suction readings or a plumbing-based estimate, then view pump curves, estimated operating flow and turnover for the selected pump and speed assumptions.
How to use this calculator
The interactive charts help show why horsepower alone does not identify operating GPM. The useful comparison is where a pump curve meets the system curve. This tool includes selected Pentair, Jandy and Hayward curves so you can explore different pumps using the same system assumptions.
- Choose gauge-reading or plumbing-estimate mode and enter your flow reference.
- Enter appropriate pressure and suction measurements, or pipe lengths, diameters and equipment losses.
- Select pump curves and speed assumptions, then review the estimated operating points.
Worked example
Using a discharge reading of 15 psi and suction vacuum of 5 inches of mercury, with zero correction, gives approximately 40.30 feet of head: (15 × 2.31) + (5 × 1.13). Measurements need appropriate locations and the same operating condition. A filter gauge alone does not describe every part of the system.
Example inputs illustrate the calculation. Enter your own measurements, product directions and rates to plan your pool.
Turn your result into a plan
Use the chart as a comparison aid, then check motor voltage, controls, plumbing, filtration limits and required equipment flow. An operating-point estimate should be confirmed against the current manufacturer curve and, where available, actual flow measurements before selecting equipment.
Explore related equipment
Review these product pages as part of your equipment planning. Confirm model, installation and system compatibility before ordering.
Jandy VS FloPro Variable Speed Pump, 2.7 HP, 230/115 V, 2 AUX Relays, No Controller | VSFHP270DV2A
View product details →Frequently asked questions
What is total dynamic head?
TDH describes the head the pump must overcome at a particular flow. Resistance changes as flow, valve positions, pipe routing and equipment conditions change, so it is not one fixed property for every operating speed.
Can I calculate TDH from filter pressure alone?
Not reliably for the complete system. Suction conditions, gauge locations and any required correction matter. Use readings taken at appropriate locations and review the measurement method with your installer.
Are the pump curves exact manufacturer selection tools?
The chart uses approximate digitized curve points. Speed changes use affinity-based estimates. These help compare behavior, but final selection requires the manufacturer’s current data for the exact pump and configuration.
Will reducing speed preserve the same flow?
Generally the estimated operating point changes when the pump curve changes. Review the new flow against the heater, sanitizer, cleaner and filtration requirements rather than assuming the original flow remains available.
Continue your pool planning
Need help choosing pool equipment?
Send Pool Supply Depot your pool size, calculator results and existing equipment details. We can help review product options and the information to confirm with your installer. Based in Henderson, Nevada, we serve pool owners and pool professionals nationwide.
Pentair Pool and Spa Equipment
Pentair is renowned for its innovative and energy-efficient pool and spa equipment. From pumps to heaters, Pentair offers a range of products designed to enhance your pool experience.
Hayward Pool and Spa Equipment
Hayward is a trusted name in the pool industry, known for its durable and high-performance equipment. Whether you're looking for filtration systems or automation, Hayward has you covered.
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