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Calcium hardness calculator

1.2 lb (545 g) of 77% calcium chloride raises calcium hardness 10 ppm in 10,000 gallons. Plaster pools want 250 to 450 ppm; vinyl and fiberglass need much less.

Calcium hardness calculator

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36lb

of Calcium chloride flake 77%

577 oz16 kg

Raises calcium hardness from 150 ppm to 350 ppm in 15,000 gal. Recommended for this surface: 250 to 450 ppm.

Add it in 2 parts

  1. Add 18 lb.
  2. Wait 60 minutes with the pump running, retest, then add 18 lb if you still need it.
  • This is a large change. Add it in stages and retest between them.
  • Dissolve it in a bucket of pool water first, then pour it in front of a return jet.
  • Calcium chloride gets hot when it dissolves. Add it to a bucket of water, never water onto the flakes.

Check the product label. Strengths vary by brand, so enter the % printed on yours. Add one chemical at a time, into the water, and never mix chemicals.

Save this test and get reminded when it is time to retest.

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Adding calcium chloride

  1. Fill a bucket with pool water first.
  2. Add the flakes to the water, never the water to the flakes. It gets hot as it dissolves.
  3. Pour it around the deep end with the pump running.
  4. Add no more than about 100 ppm at a time, then retest after a few hours.

Targets by surface

SurfaceRange
Plaster, pebble, tile250 to 450 ppm
Fiberglass150 to 350 ppm
Vinyl50 to 350 ppm
Acrylic hot tub100 to 250 ppm

Questions

How do I lower calcium hardness?

Only by replacing water with softer water. The drain and refill calculator shows how much.

Does cal-hypo shock raise calcium?

Yes, about 0.7 ppm of calcium per ppm of chlorine.

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