Pool Pump Size Calculator
Calculate the required GPM flow rate, total dynamic head, and recommended pump horsepower for your pool.
Turnover Rate Comparison
| Turnover (hrs) | Required GPM | Head Loss (ft) | TDH (ft) | Recommended HP |
|---|---|---|---|---|
| 6 hours | 56 | 10.9 | 20.9 | 1 HP |
| 8 hours (selected) | 42 | 8.2 | 18.2 | 0.75 HP |
| 10 hours | 33 | 6.4 | 16.4 | 0.5 HP |
| 12 hours | 28 | 5.5 | 15.5 | 0.5 HP |
How It Works
This calculator determines the right pump size for your pool by analyzing your plumbing system. It calculates the required flow rate (GPM) based on your pool volume and desired turnover rate, then estimates friction losses through your pipes and fittings to determine total dynamic head.
Required GPM = Pool Volume / Turnover Hours / 60 minutes. For example, a 20,000-gallon pool with an 8-hour turnover needs about 42 GPM.
Head loss accounts for friction in the pipes, elbows, and fittings. Smaller pipes create more friction, requiring a more powerful pump. Total dynamic head (TDH) adds filter and equipment resistance (approximately 10 ft) to the friction loss.
The recommended HP is based on both the required GPM and TDH. Oversizing a pump wastes energy and can damage equipment, while undersizing leads to poor circulation and water quality issues.
Frequently Asked Questions
What size pool pump do I need?
Pool pump size depends on your pool volume, plumbing diameter, pipe run length, and desired turnover rate. Most residential pools need a 1 to 2 HP pump. Use this calculator to find the exact GPM and HP your pool requires based on your specific plumbing setup.
How many hours should a pool pump run per day?
Most pool pumps should run long enough to turn over the entire pool volume at least once per day. For residential pools, an 8-hour turnover is standard. In hot climates or pools with heavy use, a 6-hour turnover may be needed. Running the pump longer improves water clarity but increases energy costs.
What is total dynamic head (TDH)?
Total dynamic head (TDH) is the total resistance the pump must overcome to circulate water through the plumbing system. It includes friction loss from pipes and fittings, vertical lift, and resistance from the filter and other equipment. A higher TDH means the pump has to work harder, requiring more horsepower.
Is a variable speed pump worth the investment?
Yes, variable speed pumps are typically worth the investment. They can reduce energy costs by 60-80% compared to single-speed pumps by running at lower speeds for longer periods. Many states now require variable speed pumps for new installations. They also run quieter and extend the life of your filter.