Hot Tub Things® Calcium Increaser – Spa Hardness Booster
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Precision liquid formula raises spa water calcium hardness efficiently, helping prevent corrosive “hungry” water that can damage heaters, plumbing, and metallic parts.
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Ideal for weekly use or fresh fills in spas with low or softened water, restoring balance without overshooting to scale-forming levels.
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Helps minimize foam, cloudiness, and sanitizer demand by maintaining stable hardness—essential for optimal sanitizer effectiveness.
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Compatible with all hot tub sanitizer types—including chlorine, bromine, saltwater, and mineral systems—simplifying your chemical routine.
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Convenient 32 oz bottle with marked dosing lines makes it easy to add precise amounts based on spa volume.
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Backed by Hot Tub Things’ quality assurance, safety-tested for spa use and formulated without harsh fillers—trusted by professionals and DIYers.
Frequently Asked Questions
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Test your calcium hardness monthly. Most hot tubs need calcium increaser added every 2-4 months, depending on water source, evaporation, and refill frequency. If you use soft water or frequently drain and refill your spa, you may need to add it more often.
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Low calcium hardness (below 150 ppm) creates corrosive water that can etch plaster, damage acrylic surfaces, corrode heaters and pumps, and cause foaming. It can also make water feel "soft" or slippery and reduce the effectiveness of sanitizers.
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As a general rule, add 1 ounce of calcium increaser per 100 gallons of water to raise calcium hardness by approximately 7 ppm. Always test first, calculate your needs, and add gradually while circulating water.
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Yes! Hot Tub Things® Calcium Increaser works perfectly with saltwater systems, chlorine, bromine, and all other sanitizer types. It won't interfere with your salt cell or water chemistry.
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Absolutely. While formulated for hot tubs and spas, this calcium increaser is also suitable for swim spas, plunge pools, and small above-ground pools.
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They're the same product. "Calcium increaser," "calcium hardness increaser," and "spa hardness booster" all refer to calcium chloride products designed to raise calcium levels in spa water.
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