TL;DR
Calcium hardness is the concentration of dissolved calcium in pool or spa water, measured in parts per million, with 200 to 400 ppm the accepted range for plaster pools and slightly lower targets for vinyl and fiberglass. Below range, hungry water dissolves calcium out of plaster, grout, and stone, etching surfaces; above it, the excess precipitates as scale on tile lines, filters, and heater exchangers and turns water cloudy.
What it means
Calcium hardness is the concentration of dissolved calcium in pool or spa water, measured in parts per million, with 200 to 400 ppm the accepted range for plaster pools and slightly lower targets for vinyl and fiberglass. Below range, hungry water dissolves calcium out of plaster, grout, and stone, etching surfaces; above it, the excess precipitates as scale on tile lines, filters, and heater exchangers and turns water cloudy. It rises through evaporation and calcium-based chlorine and is lowered only by draining and diluting, so arid-climate pools drift upward over time. Service techs test it monthly and factor it into the saturation index that governs overall water balance.
Where it sits in the glossary
Calcium hardness is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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