How to Size a Pool Pump Correctly
Sizing a pool pump is about finding the right balance. The goal is to select a pump that can filter the entire volume of your pool in a desired timeframe (the "turnover rate") while overcoming the friction in your plumbing system (the "Total Dynamic Head").
The required **Flow Rate** in Gallons Per Minute (GPM) is calculated first. Then, based on the system's resistance (head), we can find the smallest horsepower (HP) pump that can provide that GPM. Choosing an oversized pump is a common mistake that leads to high energy costs and potential damage to your filter.
Recommended Turnover Times
| Pool Type | Recommended Turnover |
|---|---|
| Residential Pool | Once every 8-10 hours. |
| Commercial / High-Use Pool | Once every 6 hours. |
| Spa / Hot Tub | Once every 30 minutes. |
How to Use the Calculator
- Enter the total volume of your pool in US Gallons.
- Select a desired turnover time. 8 hours is standard for residential pools.
- Choose a system resistance level. Most standard in-ground pools with equipment located nearby are "Medium". Choose "High" if you have a rooftop solar heater or complex plumbing with many features.
- Click "Calculate Pump Size" to see the required flow rate and a recommended pump horsepower.
Frequently Asked Questions
What is "Total Dynamic Head" (TDH)?
TDH is a measure of the total resistance in your pool's plumbing system. It includes friction from the length and size of the pipes, plus resistance from every fitting (elbows, tees), the filter, heater, and any water features. It's measured in feet of "head". A higher TDH requires a more powerful pump to achieve the same flow rate.
Should I get a single-speed or variable-speed pump?
Variable-speed pumps (VSPs) are now required by law in many regions for new installations and replacements. While more expensive upfront, they are far more energy-efficient. They can run at lower speeds for longer periods to achieve the same turnover, drastically reducing electricity costs. This calculator recommends a horsepower rating, which can be used for either type, but a VSP is highly recommended.