Maintaining proper levels of calcium hardness in your swimming pool is essential for the structural health of the plaster and the clarity of the water. Adding calcium chloride to your pool will increase the calcium hardness, or the concentration of dissolved calcium, of your water. The North Carolina Department of Environment and Natural Resources states that the proper range of calcium hardness for most plaster pools is about 250 parts per million (ppm). Vinyl pools require less calcium chloride.
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Check the level of calcium hardness in your pool. Test kits are available in most pool supply stores, or you can have a professional come and test your water for you. You will need the test results before adding calcium chloride to your pool.
Use 2 oz. of calcium chloride for every 1,000 gallons of water to raise the ppm by 10. For example, if your pool holds 10,000 gallons of water, and you wish to raise the ppm by 20, you must add 40 oz., or 2.5 lbs, of calcium chloride to the water.
Dissolve the calcium chloride in a large plastic bucket of water. Do not add the calcium chloride directly to your pool water. Doing so can cause scale to form on the pool surface.
Pour the solution into your pool. Do not add more than 10 lbs of calcium chloride per 10,000 gallons of pool water at one time. Wait at least 12 hours before adding more.
Brush your pool to mix the water and stir up undissolved material that has collected on the bottom.
Retest the water 12 to 24 hours after adding calcium chloride to verify that you have obtained proper levels.