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 answer, the drawings, every reading and every table on this page are worked for the values in these fields, and worked again as you type. The questions further down are answered for the example this page was published with.

At 21,100 gal

Every product that does this

Every product with a fetched strength that moves this reading by 120 ppm. A row we can compute a quantity for comes first.
Product Add Also moves
HASA Calcium Chloride
calcium chloride 78.0% 		29.99 lb
13.60 kg		 nothing else measured

The manufacturer's own dose sentence reads: 1 lb in a 10,000 gal pool increases the calcium hardness by 20 ppm. The figures above are computed from the product's strength.

In steps, if you would rather

One dose split five ways. Add a step, run the pump, and test again before the next.
To reach Add Total added
204 ppm 6.00 lb 6.00 lb
228 ppm 6.00 lb 12.00 lb
252 ppm 6.00 lb 17.99 lb
276 ppm 6.00 lb 23.99 lb
300 ppm 6.00 lb 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 September 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.