How to Raise Calcium Hardness in Water

How to add Calcium Chloride to a swimming pool


  • Pre-dissolve all dry chemicals in water before adding them to the pool.
  • Calcium Chloride gets hot when dissolving. Use caution and safety gloves/glasses.
  • Always add chemicals to water; never water into chemicals.
  • Never throw dry chemicals directly into the pool.
  • Never allow undissolved chemicals or salt to sit directly on a pool surface.


Calcium hardness can increase in a few ways: 1) calcium chloride, 2) Cal Hypo chlorine, and 3) the water steals calcium for itself. If calcium increases but was not manually added by the pool owner or operator, you know it came from the surface or tile grout. In the case of vinyl liner or fiberglass pools, low-LSI water can cause deterioration of the surface. Calcium hardness is often under-appreciated and is essential, especially in cold water.

This procedure outlines how to add pre-dissolved calcium chloride to water.

Related Article: How to add Calcium Chloride to a swimming pool

You will need:

  • Test kit
  • Liquid and Dry measuring cups
  • Protective gear (glasses, rubber gloves)
  • The Orenda App
    At least one clean bucket (or the Orenda Startup Barrel™)
    • One clean garden hose to fill the barrel
    • Channel locks large enough to unscrew the 2" drain plug at the bottom of the barrel
  • Calcium Chloride (Flake or Prill/Granular)
  • Muriatic Acid
  • Orenda SC-1000
  • Stirring stick


  1. Bring your test kit, measuring cups, and chemicals to the pool, and collect a half-full bucket of water.
  2. Test the water for pH and calcium hardness (at a minimum). We recommend also testing for total alkalinity and water temperature.
    • If the pool water pH is 8.0 or above, you will need some acid for this procedure
  3. Once water chemistry is known, use the Orenda App to figure out the calcium chlorine dose needed.
    • If the dose is more than 15 pounds of calcium chloride, do not exceed 15 pounds in a single bucket. Instead, divide up the dose and repeat the process using multiple buckets of water until you distribute the entire dose. Alternatively, if you're using the Orenda Startup Barrel™, you can safely add up to 150 pounds of calcium chloride at a time.
  4. Add the calcium chloride to the bucket of water and stir.
  5. Add one ounce of SC-1000 to chelate the calcium and help it dissolve.
  6. Add one ounce of muriatic acid (if the water's pH is 8.0 or higher).
  7. Once the bucket completely dissolves and beginning to clear, pour it around the perimeter of the pool.
  8. Repeat the process as necessary for more significant amounts of calcium chloride.


Additional Information

If your pool requires an acid treatment to reduce pH or alkalinity, acid can be pre-diluted in the same bucket as calcium chloride. Never add acid to calcium directly, but it is okay to add acid to the bucket of water that is also dissolving calcium chloride. Always use safety gear, and remember that calcium chloride gets hot when dissolving. Use caution when handling.

Related Procedure: How to Implement the Orenda Program

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