What is calcium chloride?

Calcium chloride (CaCl2) is the chemical used to increase calcium hardness in water.

Calcium chloride (CaCl2) increases calcium hardness in water. It has many other uses in other industries too, such as ice melting and ballast weight for tractor tires. You can learn more here.


how to add calcium

Calcium chloride product types

There are three types of calcium chloride available in the swimming pool market:

  • Calcium flake (77-80%)
  • Calcium prills/granular (94%)
  • Calcium powder (94%+)

The Orenda Calculator™ offers dosing results for both flakes and prills/granular. And since the purity of powder is usually identical (or very close) to prills, that dose applies to powder too.  That said, calcium chloride powder is more rare than the other two products.

Exothermic reaction: dissolving calcium gets HOT

Be careful when pre-dissolving calcium chloride. It gets hot! We have heard from customers who added too much to a bucket at a time and the plastic began to warp. One customer put 50 pounds in a large trash can, and it melted through and ruptured...spilling everywhere. Quite the mess.

Our Startup barrel is LDPE plastic that is rated for 250ºF (water boils at 212º). If you want the exact scientific answer, the hottest calcium chloride dissolving can get is -81.3 kJ/mol. That same source says calcium chloride can get up to 51ºC/123.8ºF.

And that lines up really well with our experience. We once used an infrared/laser thermometer and aimed it into our startup barrel after adding two bags of calcium chloride (100 pounds total). It measured between 112º and 120ºF, and never saw it get over 120ºF.

How to use calcium chloride

We recommend pre-dissolving and pre-chelating calcium chloride using SC-1000. The approximate dose rate is 1 fl.oz. of SC-1000 per 10 pounds of calcium chloride dissolved. This is not exact science, but it has shown to get the job done. If you are doing the Orenda Startup™ procedure or the post-fill Startup, take a portion of the SC-1000 purge dose for this.

Here are the relevant instructional procedures for calcium chloride:

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