What is swimming pool shock?

SKIMMER NOTES: Pool shock is a more concentrated form of chlorine that helps make your pool water safe and healthy for swimming.

What is swimming pool shock?

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  • Category:
  • Pool
  • Pool Maintenance

Are you a new swimming pool owner wondering what this stuff is that everyone’s telling you to dump into your pool? Welcome to the pool owner club; you have so much fun ahead of you and we're here to help you dive in.

So what IS pool shock?

Swimming pool shock is a powdered form of chlorine that’s used to treat your pool water to help make it safe and healthy for swimming. Shock is an important part of pool care regardless of which type of chlorine you use for daily sanitation – including salt water systems.

Now if we want to dive a little deeper, there are three types of pool shock you can buy to treat your water. The first one is called calcium hypochlorite (also referred to as cal-hypo), the second is sodium di-chlor (usually referred to as di-chlor), and then there’s liquid chlorine. They each have their advantages but all are effective in treating your pool water.

What makes shock DIFFERENT from regular chlorine? Well, granular chlorine, liquid chlorine, chlorine tablets and granular shock all have similar active chemicals that sanitize your pool; what’s different about shock is the strength of the chemical and how you're supposed to use it.

Finally, why do you need to shock your pool – or what does shock actually do when you drop it in?

When you add shock to your pool water, it gets right to work, removing the combined chlorine molecules (also called chloramines) from your pool. Shock also helps destroy bacteria and what some refer to as “bather waste” after your pool gets a lot of activity; shock removes any contamination situation, and finally, shock helps eliminate mustard, green and black algae.

For more new-pool-owner knowledge, check out our article on “How much shock do I add to my pool?”

As always, we’re here to help. If you have questions, contact our help line at 1-866-HTH-POOL or talk to our experts with our live chat!


Please read the following important reminders before adding pool chemicals to water:

• NEVER mix products together or dissolve before use.

• ONLY enter pool when FAC levels are below 4 ppm to prevent risk of bodily harm.