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How many gallons in a 20x40 pool?
About 26,900 gallons (101,900 liters), with 3 to 6 ft floor. A 20 × 40 is at the big end of residential pools, which means chemical and heating costs are higher too.
| Water depth | Gallons | Liters |
|---|---|---|
| 3 to 5 ft floor | 23,938 | 90,614 |
| 3 to 6 ft floor | 26,930 | 101,941 |
| 3 to 8 ft floor | 32,914 | 124,594 |
Surface area is 800 sq ft, and each extra inch of water adds about 499 gallons, so a level check is worth doing.
What this size needs
| Salt for a new salt system, to 3,200 ppm | 719 lb (18 × 40 lb bags) |
| 1 ppm of chlorine, 10% liquid | 1.1 qt (34 fl oz) |
| Shock to 10 ppm, 65% cal-hypo | 3.5 lb |
| Pump flow for an 8-hour turnover | 56 GPM |
| Fill time at 9 GPM | 49.9 hours |
Based on 26,900 gallons. For your exact volume, use the pool volume calculator.