In our last article we addressed the broad categories of choices available to the pool owner when it comes to shock, as well as discussing the uses and benefits of liquid chlorine shock. So let’s move on this week to another popular choice for shock – granular chlorine, in particular calcium hypochlorite. Called “cal hypo” for short, this form of chlorine has been on the market for a very long time. It was probably your grandfather’s chlorine of choice, and for good reason. This particular form of chlorine will not break down and lose potency easily or quickly on the shelf. Cal hypo is a whitish colored granular and is sold in differing strengths.

Always check labels for percentage to find out if it’s a good value – be careful of big box retailers. Like many things these days, a low price per pound is not always a bargain. Better product is often 68% or higher active ingredient, keeping fillers and buffers to a minimum. Remember that the higher the percentage of chlorine, the sooner it dissolves in water.

For safety, ALWAYS add granular chlorine to water, NEVER water to chlorine! And remember that although this is a great product for shocking the pool routinely (once per week on average is recommended), shocking later in the evening makes for great swimming the next morning. Also, be aware that since it is a calcium chlorine compound it may not be recommended for pool owners whose calcium harness level is off the charts, since excessive calcium may lead to scaling or incurable cloudy water. This is not a common occurrence, however, and usually not an issue for most pools.

Keep Swimming!