How to Raise Pool Calcium Hardness to Prevent Damage

Low Pool Calcium Hardness and Surface Damage

Objective

This guide helps you identify dangerously low Calcium Hardness levels and provides the exact steps to safely raise them, protecting your pool plaster and equipment from aggressive, corrosive water.

Satisfying the "Universal Solvent"

Water is often referred to by scientists as the "universal solvent." This means that water is always hungry and constantly seeking a perfect state of mineral equilibrium.

If your pool water has insufficient dissolved calcium (meaning it is too "soft"), it becomes highly aggressive. To satisfy its natural appetite, this hungry water will literally dissolve and suck the calcium carbonate right out of your expensive pool plaster, tile grout, and concrete. This process, called "etching," leaves your surfaces feeling like rough sandpaper. By proactively raising your Calcium Hardness, you "feed" the water the minerals it needs so it stops eating your pool.

Prerequisites

  • A liquid chemical drop-test kit capable of testing Calcium Hardness.

  • A bucket and a pool brush.

  • A supply of Calcium Hardness Increaser (Calcium Chloride).

Step-by-Step Instructions: Raising Your Calcium

  1. Test Your Current Levels: Use your drop-test kit to determine your current Calcium Hardness. For most plaster and pebble pools, the ideal safe range is 200-400 ppm. If you are below 200 ppm, you must act.

  2. Calculate the Dosage: Navigate to our Shop Products page to review the dosage guidelines on your Calcium Hardness Increaser. Generally, it takes about 1.2 lbs of calcium chloride to raise the hardness of 10,000 gallons of water by 10 ppm.

  3. Pre-Dissolve with Caution: Calcium Chloride reacts with water, generating heat. Fill a bucket with pool water first, then slowly add the calcium flakes. Never add water to the chemical. Stir carefully with a wooden stick.

  4. Broadcast the Mixture: Set your System Power to ON. Slowly pour the dissolved mixture into the deep end of the pool.

  5. Brush the Pool: Immediately use your pool brush to sweep the bottom of the pool where you poured the chemical. If any undissolved flakes settle on the plaster, they can create heat spots and cause localized damage.

  6. Circulate and Retest: Run the pump continuously for 12 hours. Retest to confirm your levels are resting safely above 200 ppm.

Troubleshooting Note: Don't Go Too High

While low calcium destroys plaster, extremely high calcium (over 600 ppm) can lead to cloudy water and scale formation. Always balance your pool using the Hamilton Index™ (keeping Alkalinity between 60-90 ppm) to ensure your water can properly hold the calcium in solution without scaling.

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