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Calcium Hardness Calculator

Calculate how much calcium chloride to add to raise your pool calcium hardness (CH).

Calcium Hardness Adjustment

Don't know? Calculate it here
Recommended: 250-400 ppm for plaster pools

Calcium Chloride Dosage

Amount to Add -- lbs
Also equals -- oz
Will raise CH to -- ppm
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How to Add Calcium Chloride:
  1. Pre-dissolve in a bucket of pool water (never add dry)
  2. Add slowly in front of a return jet
  3. Wait 24 hours before retesting
  4. Don't add more than 10 lbs per 10,000 gallons at once

What is Calcium Hardness?

Calcium Hardness (CH) measures the dissolved calcium in your pool water. Too low = water becomes aggressive and attacks plaster, grout, and equipment. Too high = scale buildup and cloudy water.

Target CH by Pool Type

Pool Surface Target CH Minimum
Plaster / Gunite300-400 ppm250 ppm
Pebble / Aggregate300-400 ppm250 ppm
Vinyl Liner150-250 ppm100 ppm
Fiberglass200-300 ppm150 ppm

CH Too Low?

CH Too High?

Lowering Calcium Hardness:
You can't chemically remove calcium. The only solution is to drain and refill with softer water, or use a reverse osmosis water treatment service.

Calcium Hardness & LSI

Calcium Hardness is a key component of the Langelier Saturation Index (LSI), which measures water balance. For plaster pools, maintaining proper CH is critical to prevent etching.

LSI Value Water Condition
Below -0.3Corrosive / Aggressive (attacks plaster)
-0.3 to +0.3Balanced (ideal)
Above +0.3Scale forming