How much salt for a 20,000 gallon pool

Starting with plain water, you'll pour roughly 534 lb of salt into a 20,000 gallon pool to hit 3,200 ppm (parts per million, the number a salt test shows). That works out to 14 bags at 40 lb each. Got some salt in the water already? Enter your reading and watch the bag count shrink.

Units Gallons, pounds Liters, kilograms

Pool volume in gallonsgal

Don't know the gallons? Measure the pool

Pool shapeRectangleOvalRoundKidney

A: lengthftB: widthftShallow end depthftDeep end depthft

The gallons above fill in as you measure.

Salt reading now ppmYour chlorinatorTarget to dose to ppm

Example For 20,000 gallons, from 0 to 3,200 ppm. Type yours to see your bags.

Buy 14 bags of

Add 534 lb in all: pour 13 bags now, then 14 lb from bag 14 after you retest.

Pump on. Pour it around the deep end, not into the skimmer.
Brush any salt off the floor until it's gone.
Run the pump 24 hours and test. Add the rest only if the reading is still short.

How this is worked out

Gallons = A × B × average depth × 7.5 for a rectangle, 6.7 for an oval and 5.9 for a round pool (diameter × diameter), the factors in Hayward's manual; 7.0 for a kidney (length × average width), from Inyo's sizing guide. Pounds of salt = (target ppm − your ppm) × gallons × 8.34 ÷ 1,000,000. A gallon of water weighs 8.34 pounds. Bags round up. In liters: kilograms = ppm difference × liters ÷ 1,000,000.

Salt for 20,000 gallons by current reading

Reading now	to 3,000 ppm	to 3,200 ppm	to 3,600 ppm
0 ppm	Buy 13 bagsadd 500 lb	Buy 14 bagsadd 534 lb	Buy 15 bagsadd 600 lb
1,000 ppm	Buy 9 bagsadd 334 lb	Buy 10 bagsadd 367 lb	Buy 11 bagsadd 434 lb
1,500 ppm	Buy 7 bagsadd 250 lb	Buy 8 bagsadd 284 lb	Buy 9 bagsadd 350 lb
2,000 ppm	Buy 5 bagsadd 167 lb	Buy 5 bagsadd 200 lb	Buy 7 bagsadd 267 lb
2,500 ppm	Buy 3 bagsadd 83 lb	Buy 3 bagsadd 117 lb	Buy 5 bagsadd 183 lb
2,800 ppm	Buy 1 bagadd 33 lb	Buy 2 bagsadd 67 lb	Buy 4 bagsadd 133 lb
3,000 ppm	Already there	Buy 1 bagadd 33 lb	Buy 3 bagsadd 100 lb

Every bag is 40 lb and the count rounds up. Pour all but the final bag, let the pump run a day, then test before you open it.

Intex and TruClear aim for 3,000 ppm, Hayward for 3,200 ppm and Pentair for 3,600 ppm. The chart by chlorinator lists every manufacturer's number.

Good to know at 20,000 gallons

In a pool this size, every 100 ppm gap takes 16.7 lb to close. So when your test reads 400 ppm under target, that's 67 lb: buy 2 bags of 40 lb.

CircuPool's advice is to buy a cell sized for 1.5 to 2 times the water you hold. For this pool that is 30,000 to 40,000 gallons, which fits the Pentair IntelliChlor LT25 or the Pentair IntelliChlor Plus30 or the Jandy TruClear or the Hayward T-CELL-15 (W3T-CELL-15) or the Pentair IntelliChlor IC40 or the Pentair IntelliChlor Plus40 (IC40 Plus) or the Jandy AquaPure 1400.

Questions people bring to the counter

How much does a backwash or a rainy week cost me in salt?

Only the water you lose takes salt with it. If a top-up brings this pool from 2,800 back to 3,200 ppm, that's 67 lb: buy 2 bags of 40 lb.

How can I tell if my pool has enough salt?

Test the water. Most chlorinators light a low-salt warning below their range. A strip or drop kit reads in ppm, and that number goes in the salt reading box.

Next size down or up: 18,000 gal or 25,000 gal. Every size is on the per 1,000 gallons chart.