Adjusting hardness

It is recommended that dry chemicals first be mixed into a generous amount of pool water in increments of about two pounds (1 kg), and the predissolved mixture be distributed evenly around the pool unless directed otherwise.

Precautions

  • Never add water to chemicals; always add chemicals to water.
  • Never add calcium chloride to skimmer since it produces heat upon mixing with water.
  • Always follow manufacturer’s recommendations and warnings on product labeling.
  • Never mix two chemicals together since their pH might vary and could cause an explosion or fire.

In most areas of the country a minimum of 150 ppm and an ideal range of 200-400 ppm of hardness is recommended. The only practical way to lower hardness is to drain some water from the pool or spa and refill with water that is lower in hardness.

Once you determine the hardness concentration, calculate how much you wish to add and find this number in the left-hand column. Match this with the volume of water in the pool or spa, listed at the top of the table. Be careful when mixing calcium chloride with water since this can generate a significant amount of heat. Allow the water to circulate 4-8 hours after the chemical is added and then check the hardness.

 

Raising Hardness with Calcium Chloride

U.S. Customary Units:

  100 Gallons 1,000 Gallons 5,000 Gallons 10,000 Gallons 20,000 Gallons 50,000 Gallons
To Raise ppm Tsp Oz Lb Oz Lb Oz Lb Oz Lb Oz Lb Oz
10 1 — 0 2 0 10 1 4 2 7 6 2
20 2.5 — 0 4 1 4 2 7 4 15 12 4
30 3.5 — 0 6 1 13 3 11 7 6 18 7
40 5 — 0 8 2 7 4 15 9 13 24 9
50 6 — 0 10 3 1 6 2 12 4 30 11
60 — 1.2 0 12 3 11 7 6 14 12 36 13
70 — 1.4 0 14 4 5 8 10 17 3 42 16
80 — 1.6 1 0 4 15 9 13 19 10 49 2
90 — 1.8 1 2 5 8 11 1 22 2 55 4
100 — 2 1 4 6 2 12 4 24 9 61 6

Metric Units:

  400 Liters 4000 Liters 20000 Liters 40000 Liters 80000 Liters 200000 Liters
ppm Kg g Kg g Kg g Kg g Kg g Kg g
10 0 10 0 60 0 290 0 590 1 180 2 940
20 0 10 0 120 0 590 1 180 2 350 5 880
30 0 20 0 180 0 880 1 760 3 530 8 820
40 0 20 0 240 1 180 2 350 4 700 11 600
50 0 30 0 290 1 470 2 940 5 880 14 700
60 0 40 0 350 1 760 3 530 7 60 17 640
70 0 40 0 410 2 60 4 120 8 230 20 580
80 0 50 0 470 2 350 4 700 9 410 23 520
90 0 50 0 530 2 650 5 290 10 590 26 460
100 0 60 0 590 2 940 5 880 11 760 29 400

 

Notes:Be sure to note chemical precautions. Always follow manufacturer’s recommendations.