Pool Shock vs. Chlorine – Is There a Difference?

During busy summer months, keeping the swimming pool clean can be a bit tough, especially if you host many poolside parties or have friends over. The more swimmers use a pool, the more bacteria, oils, hair, and other deposits are left behind in the water. Eventually, your chlorine will become saturated with the nitrogen and cease sanitizing the water efficiently. When this happens, your pool needs a good shock!

But what is pool shock, and how is that different from chlorine? If you’d like to learn how these two critical pieces of pool maintenance differ, read on!


Main Takeaways

  • Shock is a chemical used to rapidly raise the levels of free chlorine in your pool to oxidize sluggish chloramines effectively.
  • While shock and chlorine share certain active chemicals, their potencies and purposes differ.
  • The amount of chlorine needed to shock your pool depends on the gallons of water in it.
  • You should shock your pool only at night after heavy bather loads, parties, rough weather events, or to eradicate the early stages of algae.

What is Pool Shock?

Pool shock refers to a chemical used to treat the water in your pool by oxidizing the chloramines and killing contaminants, pathogens, and other unhygienic bacteria – a process known as “shocking” or “superchlorination.” Shock is sold as a powdered substance or, more accurately, a granular oxidizer. Pool shock typically comes in two types: cal-hypo and dichlor.

When chlorine molecules come into contact with the dirt and oil in your pool, it binds with the contaminant forming “combined chlorine.”

When you shock your pool, you essentially eradicate the elements of combined chlorine, which has become undesirable and ineffective as a sanitizer since the free chlorine has combined with the nitrogen and ammonia in oils, urine, or germs shed from swimmers. Combined chlorine isn’t necessarily a bad sign, however. It just means your chlorine has done what it is intended to. The powerful smell of combined chlorine is a telling sign that your pool needs a shock.

In short, pool shock is what you do to release the combined chlorine, increase the levels of free chlorine, and eradicate the bacteria in the pool in one go.

What is Pool Chlorine?

Pool chlorine is a pool sanitizer that oxidizes algae, oils, dirt, bacteria, and other unwanted elements. It is an economical and effective sanitizer and is usually sold as granules, tablets, or liquid. Generally, the recommended amount of chlorine in your water is around three ppm (parts per million). If it is too little, the water won’t be clean or safe to swim in. If it’s too much, the pH of the water gets damaged, and the water becomes more acidic, which can corrode your pool plaster or equipment. Acidic water can also be uncomfortable for swimmers.

Chlorine is one of the most important chemicals in your pool. As a pool owner, it should be a part of your regular maintenance routine to ensure you always have the proper levels of it in your pool water.

Chlorine comes in three different types: sodium hypochlorite (liquid), lithium hypochlorite (dry granular), and trichlor (tablet).

What’s The Difference Between Pool Shock and Chlorine?

Chlorine is a sanitizing agent vital for maintaining a healthy pool. On the other hand, pool shock is a very high dose of chlorine and is used to raise free chlorine levels quickly.

So, to put it shortly, the difference is that chlorine is necessary to maintain a consistent level of the chemical in water. In contrast, shock is needed to increase the levels of chlorine at a rapid pace.

Another difference is that some types of shock contain chlorine, but there are also non-chlorinated types available. But it’s worth mentioning that while non-chlorine shock is effective against gunk in the water, it will not work against bacteria or algae. So, it’s best to stick to a chlorine shock – particularly after heavy pool use.

How Are Pool Shock and Chlorine Similar?

Chlorine and shock rely on the same active chemicals that eradicate bacteria and sanitize your water. They share a similar chemical makeup and mainly vary in potency and additives. They both work to clean your pool water, sanitize it, and protect it from algae blooms.

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Frequently Asked Questions

How much chlorine do you need to shock a pool? 

The amount of chlorine needed to shock a pool depends on the gallons of water it has and the type of chlorine used. For example, if using calcium hypochlorite or trichlor, the amount of chlorine is usually one pound per every 10,000 gallons of water. However, it is important, especially if you are new to shocking a pool, to speak to a professional beforehand and get a more tailored recommendation on what amount to use for your pool. You should also check the manufacturer’s instructions for the pool shock you are using.

When should you shock a pool? 

You should shock a pool every week or so during the high-usage months. But you should also shock your pool in case of any of the following events:

  • When opening the pool after winter.
  • After a pool party or any event with high pool usage.
  • After a thunderstorm or other major weather event.
  • If there are traces of feces in your pool.
  • If you notice algae growth.
  • When your water has become cloudy or opaque.
  • After damaging weather conditions, such as high winds or heavy sunshine.
  • If your pool is not within the recommended free chlorine levels of 1-3 ppm.
  • If wild animals such as bears or raccoons have entered your pool.

Please remember: it is strongly recommended to shock your pool at nighttime when the sun has gone down. After all, you do not want the sun’s UV rays to eat away at your chlorine and reduce the efficacy of the shock treatment.

How much stronger is shock than chlorine?

Shock has an intense amount of chemical potency compared to regular liquid chlorine. The chemical concentration is much higher in shock, although it can vary depending on the manufacturer. For example, liquid chlorine has a potency of around 10% chlorine, while cal-hypo will have a potency of roughly 70%.

Can I use normal chlorine to shock a pool?

Yes, if it is urgent and you’re looking to shock your pool after a high pool use or severe weather event but do not have immediate access to pool shock, you can use normal chlorine to shock your pool. However, you will need to double-check with the manufacturer how much chlorine you’ll need to shock your pool effectively.

You can also reach out to me if you have questions. I’m here to help.

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