--- title: "What Is Hard water? Pool Glossary | Marina Pool Services" description: "Hard water is water with high calcium and minerals that can leave scale. Plain-English pool glossary from Marina Pool Services in Grapevine, TX." url: https://marinapool.multisites.ai/glossary/hard-water publisher: Marina Pool Services phone: +1-817-896-1120 quote: https://marinapool.multisites.ai/contact --- Water chemistry # Hard water Hard water is water with high calcium and minerals that can leave scale. Hard water carries a lot of dissolved calcium and magnesium. In a pool, that means faster [scale](https://marinapool.multisites.ai/glossary/scale) on tile, heaters, and salt cells, mostly in warm weather. You can test your tap water for hardness before you fill the pool. If it is high, plan to dilute with a [partial drain and refill](https://marinapool.multisites.ai/glossary/partial-drain-and-refill) when [calcium](https://marinapool.multisites.ai/glossary/calcium-hardness) climbs. Keep [pH](https://marinapool.multisites.ai/glossary/ph) and alkalinity in range so scale does not form. Test your fill water each time you top off the pool, since the minerals add up over a season. [Marina can helpPool Maintenance Services](https://marinapool.multisites.ai/our-services/pool-maintenance-services) ## Related terms - [Calcium hardness](https://marinapool.multisites.ai/glossary/calcium-hardness) - [Scale](https://marinapool.multisites.ai/glossary/scale) - [Fill water](https://marinapool.multisites.ai/glossary/fill-water) - [Partial drain and refill](https://marinapool.multisites.ai/glossary/partial-drain-and-refill) ## Need a hand with your pool? Call or text and tell us what your pool needs. Estimates are free for qualifying services, and same-day estimates are possible when the schedule allows. [Call (817) 896-1120](tel:+1-817-896-1120)[Get a quote](https://marinapool.multisites.ai/contact) ![A pool technician working on an equipment pad](https://marinapool.multisites.ai/_astro/technician-equipment-pad.BW5xZMNY_Zum1K5.webp)