1 ppm = 1 part per million by weight Water density = 8.34 lbs per gallon
The bag counts round up to the nearest whole bag since partial bags are easy to store for future top-offs. Buy exactly the number of bags shown to reach your target without going over.
Example Calculation
Tom opened his 18×36 rectangular pool after winter. His test kit reads 900 ppm and his Hayward SWCG recommends 3,200 ppm. His pool holds approximately 18,000 gallons.
Pool volume18,000 gallons
ppm needed3,200 − 900 = 2,300 ppm
Salt = 18,000 × 2,300 ÷ 1,000,000 × 8.34345.2 lbs
Buy 9 × 40 lb bags (360 lbs)
Tom will have a small amount of salt left over after the 9th bag. He can store the remainder for top-offs later in the season as water splashes out or is lost through backwashing.
Common Mistakes to Avoid
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Testing right after adding salt
Salt needs time to fully dissolve and circulate. Always wait at least 24 hours with the pump running before retesting. Testing too soon gives a falsely low reading.
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Using impure salt grades
Rock salt contains minerals and impurities that can cloud pool water and damage the chlorine generator's cell over time. Always use pool-grade or food-grade 99.8% pure sodium chloride.
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Adding all salt in one spot
Dumping all bags into one location creates a concentrated zone that can bleach your liner or finish. Broadcast salt evenly around the perimeter while walking.
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Running the SWCG at low salt levels
Most chlorine generators shut off below 2,500 ppm as a protection measure. Running the generator at low levels can damage the electrolytic cell. Wait until salt is in range before switching it on.
Pool & Hot Tub Alliance: Saltwater Pool Maintenance Guidelines
Industry guidelines for salt concentration ranges, SWCG operational parameters, and salt type specifications for residential pools.
2
US Geological Survey: Water Density and Weight Reference
Source for the 8.34 lbs/gallon water weight constant used in the ppm-to-pounds conversion formula.
HR
Hassaan Rasheed
Developer and Researcher, CalculatorFlux
Researches and verifies the formulas, methodology, and source data behind each calculator on CalculatorFlux. All tools are built and checked against the cited references before publication.
Last updated: May 2026
Salt Level Guide (ppm)
0 – 500None / Fresh water
500 – 2,700Below SWCG range
2,700 – 3,400Ideal (most SWCGs)
3,400 – 4,500Running high
4,500+Too high, dilute
SWCG Target Ranges
Hayward AquaRite2,700–3,400 ppm
Pentair IntelliChlor3,000–3,500 ppm
Jandy TruClear3,000–3,500 ppm
CircuPool RJ3,000–4,000 ppm
Generic / unknown3,000–3,200 ppm
Pro Tip
Buy one extra bag beyond your calculated amount. Salt added gradually absorbs test error. A 15,000-gallon pool at 3,200 ppm holds about 375 lbs of salt, and adding 40 lbs extra only raises the level by about 85 ppm.