Calcium Hardness Calculator
Calculate how much calcium chloride to add to raise your pool calcium hardness (CH).
For educational purposes only. Always test your water and consult product labels before adding chemicals. See our Terms of Service.
My Pool Settings
Climate & Cover
Typical Chemistry
Pre-fill calculators with your usual levels (optional)
30-50 chlorine, 70-80 SWG
60-80 recommended
250-350 recommended
Equipment
Select your equipment to personalize checklists
CALCIUM CALC
Calcium Hardness Adjustment
Recommended: 250-400 ppm for plaster pools
Calcium Chloride Dosage
Amount to Add
-- lbs
Also equals
-- oz
Will raise CH to
-- ppm
Buy Calcium Chloride on Amazon
How to Add Calcium Chloride:
- Pre-dissolve in a bucket of pool water (never add dry)
- Add slowly in front of a return jet
- Wait 24 hours before retesting
- 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 / Gunite | 300-400 ppm | 250 ppm |
| Pebble / Aggregate | 300-400 ppm | 250 ppm |
| Vinyl Liner | 150-250 ppm | 100 ppm |
| Fiberglass | 200-300 ppm | 150 ppm |
CH Too Low?
- Water etches/dissolves plaster (looks rough, pitted)
- Grout and tile deterioration
- Metal corrosion (heater, ladder, pump)
- Liner can become brittle over time
CH Too High?
- Scale buildup on tile line
- Cloudy water
- Scale in heater (reduces efficiency)
- Salt cell scaling (SWG pools)
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.
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 -0.3 | Corrosive / Aggressive (attacks plaster) |
| -0.3 to +0.3 | Balanced (ideal) |
| Above +0.3 | Scale forming |