How To Shock A Swimming Pool


In this article you’ll learn how to shock a pool, we’ll also talk about some of the most important things related to shocking a pool, and you’ll find out what pool chemicals are the best options for shocking a pool.

It may sound complicated and complex, especially if you are just the beginner looking for advice on pool maintenance, but by following this step by step article the question of how to shock a pool won’t be such an enigma and problem, and when you start using this knowledge in practice you’ll see it is not that complicated and scary. It will eventually become a routine and something you’ll be doing without much effort.

Why You Should Shock Your Pool?

Regular pool maintenance is the essential part of keeping your swimming pool clean and healthy, so you could use it without having to worry about any possible negative outcome like skin rash or some other sign of an unhealthy environment.

When you master the knowledge of how to shock a pool, doing it regularly will prevent algae from forming and bacteria from spreading around your water, but that’s not all. Have you ever felt that horrible smell you’ve mistaken for chlorine? The one who brought tears to your eyes? Well, that smell doesn’t come from chlorine but chloramine, the chlorine, and hydrogen derivate, and it is the sign that something is wrong with the water. They form when they mix with sweat, oils, even possible urine. Chloramines could irritate your skin, eyes, lungs… So, shocking your pool is, in simple words, fighting the chloramines by adding enough chlorine to remove them and destroy their build-up.

The Difference Between Free And Total Chlorine

OK, let’s say you’ve been to a swimming pool shop and that you’ve bought the chlorine, but now you see terms like free chlorine, combined chlorine, total chlorine, and breakpoint chlorination. This may sound confusing at first, but the next few lines will clear things up and show you how simple it really is.

  • Free chlorine (FC) represents the chlorine still active in disinfecting your water. The needed level for your chlorine to do its work is between 1 and four parts per million (ppm).
  • Combined chlorine (CC) is the number of used chlorine that is still in the water. It means that the chlorine is still present, but it has been used. The wanted level of CC in your swimming pool is less than 0.2 ppm.
  • Total chlorine (TC) is those two values combined. You’ll find the FC and TC using your pool water testing kits. The CC level is the difference between these two.
  • Breakpoint chlorination is the goal. It means enough FC is roaming around your pool and fighting the chloramine. For your personal orientation and to know how much FC you’ll need, measure the amount of CC in your pool and multiply it by 10.

What happens if you fail to reach the breakpoint when you shock your pool? The probable outcome most likely will be the rise of chloramines. If that happens, what should you do? Well, it depends. The best-case scenario will end up with you adding some more chlorine to raise the FC amount and fight the chloramines. The worst-case scenario – you’ll have to empty your pool, give it a thorough cleaning to remove any possible algae or old water remains, and then replace the water with the fresh one.

Pool Shock Types

Besides the chlorine tablets, you’ll have to add some other products to kick the chlorine levels up.

Calcium Hypochlorite

One of the most used and popular products, it has been around for almost a century, it is not expensive and quite easy to use. Its chlorine value is between 65 and 75%.

How to use it:

  • Before you add it to the swimming pool, you’ll have to dissolve it.
  • You’ll have to use it after the sunset.
  • With every ppm of FC added to your water comes around 0.8 ppm of calcium, so be careful if the calcium level is high already.
  • You’ll have to wait at least 8 hours before you can use your pool again.

Lithium Hypochlorite

If the calcium level is already high, lithium hypochlorite is a better choice. It does cost a bit more, but it also has its own advantages that could fit you good.

  • It dissolves quicker than calcium hypochlorite, so you won’t have to dissolve it first, you could add it directly to your swimming pool.
  • Most versions contain about 35% chlorine.
  • You’ll have to use it after the sunset.
  • You’ll have to wait around 8 hours before you enter your swimming pool again.
  • It could potentially be toxic to water life, so you should be careful when getting rid of the recently treated water.
  • It is a good algaecide.


If you really want to know its full name, it is chloro-s-triazinetrione or dichloroisocyanuric acid, so we’ll stick with dichlor shock. It can be quite easy to use, but you’ll have to check with the specific brand. Some allow being added directly to the water.

  • Most of them contain somewhere between 50 and 60% chlorine.
  • It can be used for regular chlorine doses and shock treatments
  • You most likely won’t have to dissolve it before adding it to the water.
  • It adds about 0.9 ppm of cyanuric acid for every ppm of FC.
  • You’ll have to use it after the sunset.
  • Before you use your pool again, wait at least 8 hours.

Non-Chlorine Shock

In case you’ll have to shock the pool but would love to be able to use it as soon as possible, ask for potassium peroxymonosulfate. It is fast, it is not expensive, and it serves as a great pool shocking alternative.

  • You could add it directly into your swimming pool, day or night.
  • You’ll have to wait between 15 minutes and half an hour before you use your pool again.
  • It won’t remove algae because it doesn’t include chlorine and it is not an algaecide.

Why You Have To Shock Your Pool During The Night


Now you’ve learned that swimming pool shock products based on chlorine have to be used during the night time, you probably wonder why. The reason is the fact that the sun burns off the unstable chlorine rather quickly. By doing it during the night time, you’ll allow them to do their job without having to worry about the sun affecting the process.

How Often And When You Should Shock Your Pool

The bad smell of the water or the itchy eyes is a certain clue the time has come to shock your pool, but you won’t have to wait for it to happen. The recommended period between two shocks is one week, and doing this will keep your water chemistry well balanced, but it may also depend on the pool usage. Simply – the more it’s being used, the more often you’ll have to shock it. Sometimes even twice a week:

  • Having a pool party will require shocking the pool afterward
  • Heavy rainstorm with strong winds, especially if your pool ends up with lots of debris or bugs
  • If the water level changes rapidly.
  • In case a urine-related or other toilet-related accident happens

With the help of extra shock, you’ll get rid of algae that could form, while also removing other contaminants and unwanted materials, like body oils, sweat, etc. It is better to act before than to let them spread and damage the water quality.

Step By Step Guide On How To Shock A Pool

You’ve learned what products you’ll need, how those chemicals work, why you have to shock your pool, and how often you should do it. Now, the only thing left is to learn how to do it properly.

  1. Always shock your pool during the dark! It doesn’t matter if it is 7 pm or 3 pm, as long as you do it while the sun is down. The optimal time for the pool chemicals is from around 9 pm to 5 am. This is also good because you’ll be able to use it right in the morning if your pool test strip shows good results.
  2. Buy all the supplies you need. Create a checklist and scratch the one you’ve got, so you start your activity fully prepared. Here’s what you’ll need:
  • Protective glasses, to prevent the chemicals from reaching your eyes.
  • Protective gloves, to keep the chemicals from reaching your hands
  • Closed-toe shoes, to protect your feet
  • Pants and shirt with long sleeves you’re willing to ruin
  • Swimming pool test kit
  • Pool shock products you’ve chosen
  • Wooden stick or a spoon to stir the chemicals if you have to dissolve them before you add them to the water
  • Empty 5-gallon bucket
  1. It is time to calculate! You’ll have to find out how much water your pool has. That information may be available in your pool info book or at the manufacturer’s website, but if you don’t know how to find it, you could simply find a pool volume calculator online and try it out.
  2. Put on your protective outfit.
  3. Test the pool water for FC and TC. When you’re done, subtract those two and you’ll have the amount of CC in your pool. It’ll directly determine how much shock you’ll need.
  4. Read the manual you’ve got with the shock package. Most of the time there will be a chart with all the information, but sometimes you’ll have to do it by yourself, and this is how to do it:
  • Subtract the FC number from the TC and you’ll get CC
  • Multiply the CC number with 10
  • Subtract the FC from that number
  • Check the package and find how many ounces of shock should produce a one ppm change on 10.000 gallons of water.
  • Divide the volume of your pool by 10.000 gallons.
  • Multiply chemical change with divided pool number and the difference you’ve got from CC/FC.
  • Divide that number by 16 so you get the final results in pounds. This is the answer to how much pool shock you’ll need.
  1. Dissolving the shock should start with a ¾ bucket filled with warm water. Add the shock to that water and stir it until you see it has dissolved. It is recommended to add the shock gradually, not all at the same time, so it dissolves easier and more thoroughly.
  2. If you don’t have to dissolve your shock, count the containers you’ll need, and start by adding one bag at a time until you’ve reached the desired amount.
  3. To achieve better pool coverage and shock distribution, walk around the pool while adding the shock chemicals.
  4. Don’t use the pool before the suggested time has passed. If it says about eight hours, wait for the full eight hours. This way you’ll avoid the risk of getting your skin or your eyes irritated, or even getting your swimsuit bleached.

How To Stay Safe During The Pool Shocking

You are well aware now that swimming and all the other water-related activities are fun as long as you do your best to stay safe. This also includes any activity related to the pool chemicals. If used wrong, they could become extremely dangerous and harmful, and if you don’t store the chlorine right it could even blow up.

That is why it is almost essential to always, no matter what, have your protective glasses, gloves, shirt, and shoes on. Another reason is the ability of some of those chemicals to produce small amounts of unpleasant gas you won’t love to have near your body.

Try not to breathe from the containers or you may damage your lungs and your throat. If you want, you could use a dust mask, but keeping your nose and mouth away from the container will do.

Never mix the pool shocks or you may cause something to go south and always follow the instructions on how to add the chemicals.

Globo Surf Overview

Shocking the pool is not that hard, but yes, you’ll have to remind yourself how to do the math. Besides that, if you follow all the safety instructions and the procedure we’ve mentioned above, you’ll be having lots and lots of a great time in your pool without having to worry about the water quality and overall health. What more could you ask for?

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Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!