poolchemistrycalc

Raise calcium hardness

Into 21,100 gal of water, add

29.99lb 13.60kg

HASA Calcium Chloride — calcium chloride, 78.0%. Calcium hardness from 180 ppm to 300 ppm.

Calcium hardness on one scale: the band 150–400, the ideal band 200–400, the reading now at 180 ppm, and an arrow to 300 ppm carrying 29.99 lb. reads now 180 ppm target 300 ppm ideal code 150 200 400 400 29.99 lb +120 ppm with HASA Calcium Chloride

Your pool

feet, the long side
feet
inches of water, not wall height
inches of water
what your kit reads
where you want it

The quantity, the drawing, every product row and every step on this page are worked again as you type.

At 21,100 gal

Every product that does this

This product makes the whole change of +120 ppm on its own.
Product Add Also moves
HASA Calcium Chloride
calcium chloride 78.0% 		29.99 lb
13.60 kg		 nothing else measured

The HASA Calcium Chloride label says: “1 lb in a 10,000 gal pool increases the calcium hardness by 20 ppm”.

In steps, if you would rather

Split into 5 equal steps of 6.00 lb each: add one, run the pump, and test again before the next.

To reach Total added
204 ppm 6.00 lb
228 ppm 12.00 lb
252 ppm 17.99 lb
276 ppm 23.99 lb
300 ppm 29.99 lb

Where the band comes from

Source Range
COMAR 10.17.01.45 A(3)
conventional pool 		150–400 ppm
COMAR 10.17.01.45 A(3)
spa or hot tub 		150–400 ppm

Pool and spa rules are adopted and amended state by state, and most of the ranges here are written for public pools. Confirm every figure against the code your jurisdiction has adopted and against your own product label.

Other adjustments

Updated October 2026

Sources and dates

Ranges are quoted from the code named beside them, product strengths from the manufacturer's own product page, each retrieved on the date shown.

This site publishes calculated water volumes and chemical quantities for home pool and spa owners. It is not a health, safety or professional service, and it does not replace the instructions printed on the product you are holding. Not affiliated with, endorsed by or sponsored by HASA, Pyrock Chemical, Pentair, Hayward, Sonoma Hot Tubs, the Centers for Disease Control and Prevention, or any state health department. Product names are the trademarks of their owners and appear here only to identify the strength of what is in the container.