Ideal pool calcium hardness range
What is Calcium Hardness?
Calcium hardness measures the concentration of dissolved calcium in the water, which affects how the water interacts with plaster, grout, and metal surfaces.
Why it matters
Water that's too soft (low calcium) can pull calcium out of plaster and grout over time, etching surfaces; water that's too hard can deposit scale on surfaces, tile, and equipment.
How to raise CH
Add a calcium hardness increaser (calcium chloride) gradually — it releases heat as it dissolves and can cloud the water briefly.
How to lower CH
Partially drain and refill with fresh, lower-hardness water, or use a sequestering agent to keep existing calcium from depositing as scale; there's no chemical that directly removes dissolved calcium.
How often to test
Monthly is typically sufficient outside of plaster pools, which most pool professionals recommend checking more often since plaster is more sensitive to imbalance.
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Related parameters
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