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For new pool owners as well as old hands with years of swimming pool experience, shock chlorination may seem intimidating.

That’s perfectly normal.

When dealing with larger amounts of chemicals, everyone is a little nervous. But don’t worry. With practical experience and our tips, you can.

Once you have the basic knowledge and have gone through the process a few times, a routine will quickly set in. Pool shock chlorination is also very important because it will help you fight algae, bacteria, and ensure an odorless pool.

What is pool shocker anyway?

Pool shockers and the benefits of them can be explained quite simply. For this, remember the last time you were near a hotel pool. The pool’s chemical smell wasn’t exactly inviting, right?

Many people mistake this smell for chlorine. In fact, the cause of the penetrating chemical smell is a substance called chloramine. The fact that it smells at all is a sign of improperly treated pool water.

The chloramine not only provides the chemical smell, but also irritation to the skin and eyes. Pool shock chlorination involves adding chlorine or other chemicals to the water to destroy the molecular structure of chloramine.

Basics: The pool and chlorine

Before we dive deeper into shock chlorination, you should be familiar with the basics. The terms free chlorine, combined chlorine, and total chlorine seem confusing at first, but they are important for proper dosing during shock chlorination.

  • Free Chlorine (FC): Free chlorine is the portion of the chemical that is truly active and acts as a disinfectant to keep your pool clean. The percentage of the chemical should be between 1 and 4 ppm.
  • Combined Chlorine (CC) / Chloramines: Combined chlorine is the chlorine that has been used up. It still has a small but greatly reduced disinfection effect. The percentage of combined chlorine should be less than 0.2 ppm. Combined chlorine is the cause of the typical “swimming pool smell”, eye redness and irritation of the skin and respiratory tract.
  • Total Chlorine (TC): Total chlorine is the sum of free and combined chlorine.
    Use a test kit to determine the concentration of free chlorine (FC) and total chlorine (TC). The combined chlorine (chloramines) is the difference between these two values.

To attack the molecular structure of chloramines, a tenfold amount of free chlorine is required. Therefore, you must add an appropriate amount of pool shocker to achieve this ratio.

If the amount of free chlorine in the pool is not sufficient, the chloramine will not dissolve and more of the combined chlorine will form over time. The problems such as chemical odor and irritation become even more severe. You may even need to replace some or all of the pool water.

Types of pool shockers

Shock chlorination cannot be done with your regular chlorine. You need special pool shockers and of these, there are four different types.

Calcium hypochlorite

Calcium hypochlorite, or Cal Hypo for short, is the cheapest and most common substance used for shock chlorination of pools.


  • Pool shockers with calcium hypochlorite contain about 65% free chlorine.
  • To avoid bleaching, the agent must be dissolved in a container beforehand.
  • Wait eight hours after treatment before swimming in the pool again.
  • For every ppm of free chlorine (FC), the calcium hypochlorite-based pool shocker adds 0.8 ppm of calcium to the pool. Therefore, you should be cautious if the calcium level is already high.
  • Calcium hypochlorite pool shocker must be used after dark.

Lithium Hypochlorite

Lithium hypochlorite is especially useful in waters with a high calcium content. The substance also dissolves faster, but is also slightly more expensive than calcium hypochlorite pool shocker.


  • Lithium hypochlorite pool shockers typically contain 35% free chlorine.
  • The agent does not need to be dissolved beforehand.
  • Eight hours will pass before you can safely swim again.
  • Lithium hypochlorite pool shocker is applied after dark.
  • Pool shockers on this basis are toxic to organic life in the water. So you may be limited in disposing of the pool water, but this pool shocker is a suitable tool for algae control.


Dichlor can be added directly to the pool water without the need to dissolve it first. Dichlor pool shocker cyanic acid base (dichlor isocyanuric acid), unlike the first two types of pool shockers, can also be added to the water during the day and costs a little more money for it.


  • Dichlor pool shocker usually contains 60% free chlorine.
  • After application, do not enter your pool for eight hours.
  • Dichlor can be used for both normal chlorine treatment and shock chlorination.
  • Products from most brands do not need to be dissolved in advance.
  • For every ppm of FC, add approximately 0.9 ppm of cyanic acid to your pool.

Chlorine-free pool shock chlorinator

Potassium peroxymonosulfate provides a chlorine-free pool shocker. This method is a quick and comparatively expensive solution.


  • Dissolving the pool shocker in advance is not necessary.
  • You can use your pool again just 15 minutes after application.
  • Since the agent is chlorine-free, it does not help in algae control either.
  • You can add the agent to the water at any time of the day.

How often should you shock chlorinate the pool?

Don’t wait until the pool stinks first and bathers report skin irritation and itchy eyes to do the next shock chlorination.

Shock chlorinate your pool at least every two weeks. During the summer months, the pool load is higher (in part because more people swim in the pool). Therefore, perform pool shocking at least weekly during the summer.

Shock chlorination of the pool should also be performed after some special circumstances to keep it healthy and to clean it from chloramines and other foreign substances:

  • a heavy rain (especially if there is visible sediment in the pool after the rainfall)
  • heavy use of the pool (e.g. after a pool party)
  • a major change in the water level
  • wild animals have bathed in the pool

Pool shock chlorination is your protection against algae growth and other types of contaminants. Keep bacteria from multiplying early on and avoid compromising water quality this way.

Step-by-step guide: how to properly perform a pool shock chlorination.

Equipped with the necessary knowledge about chemistry, it’s now time for hands-on experience. Shock chlorination is not a complicated thing.

In fact, with our tips and this step-by-step guide, it’s shockingly easy. Ba dum tss.

Remember that shock chlorination can only be done at night for chlorine-containing agents. This is because unstabilized chlorine is burned by the sun and the effect of shock chlorination decreases. By working at night, you make sure that everything works as it was planned.

The pool water should not be heated or cooled before shock chlorination. Water temperatures between 15 and 18°C are considered ideal. Before treatment, remove coarse impurities from the pool and clean the filter. The optimum pH value is 7.2.


For shock chlorination, you will need to test the water, so you will need a test kit or test strips that will allow you to detect the total chlorine (TC) and free chlorine (FC) in the pool water.

Taylor K2005 High Range Swimming
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Handling large amounts of chemicals brings dangers. Protect your health with the proper equipment and your clothing from the corrosive chlorine. When handling pool shockers (chlorine based), you will need the following protective equipment:

  • safety glasses
  • protective gloves
  • old pants and old shirt (long sleeved)
  • sturdy, closed shoes
3M Chemical Splash/Impact Goggle, 1
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In addition to the pool shocker itself, you will need a wooden stick and a 20 liter bucket for dissolving.

Perform a shock chlorination:

  1. Put on your protective clothing.
  2. Test the pool water for total chlorine (TC) and free chlorine (FC) to determine how much combined chlorine (CC) is in the pool and how much shock you need.
  3. Look at the back of the package of chlorine tablets or the appropriate preparation, or visit the manufacturer’s website and follow the instructions to calculate the amount needed.

If you need to calculate the amount yourself:

  1. Find the combined chlorine (CC) content by subtracting the free chlorine from the total chlorine.
  2. Multiply the CC value by ten.
  3. Subtract the free chlorine (FC) from this product.
  4. Find how many grams of pool shocker will cause a change of one ppm in 10,000 gallons of water.
  5. Divide the volume of your pool by 10,000.
  6. Multiply the divided pool volume (step 8) by the amount of pool shock for a change of one ppm (step 7) and the missing free chlorine (step 6).
  7. Divide the result by 1000 and now you have an indication in kilograms. You must now add this amount of pool shock to your pool.

If you need to dissolve the pool shocker first:

  1. Fill a 20 liter bucket about ¾ full with warm water.
  2. Add the pool shocker to the water in 500 gram increments and slowly stir the solution with a wooden stick until the chemical has dissolved as much as possible.

Add pool shocker to the water:

  1. Pour the dissolved shocker or add the tablets evenly into the water. For a liquid pool shocker, do this slowly around the pool.

If a heel of solid particles has formed in your bucket:

  1. Add some water to the bucket by submerging it in the pool water.
  2. Gently swirl the bucket back and forth until the solid layer has dissolved, then continue pouring.

Now it’s time to wait:

  1. Turn on the filtration system and let it run.
  2. Depending on the type and manufacturer of the pool shocker, you will now have to wait a certain amount of time. As a rule, this is eight hours. Follow this instruction to avoid provoking skin or eye irritation or ending up with bleached spots on your swimsuit.


Shock chlorination is a regular part of pool maintenance. However, you must never forget that you are handling dangerous chemicals. Don’t put yourself in danger by mishandling the chemicals or not wearing enough protective gear.

Wearing protective equipment

When chlorinating the pool, wearing protective equipment is mandatory. Safety glasses and gloves are most important. Otherwise, with chlorine in liquid form, drops can splash onto the skin – or worse, into the eyes. Splashes on clothing are not a health concern, but will cause faded spots.

Storage of pool shockers

Storing pool shockers incorrectly can even lead to explosions, so you better pay close attention with these tips.

Never mix different pool shockers. By doing so, you may save yourself storage space, but you’re also setting the stage for a science experiment that could very well end up explosive.

Store pool shockers in a cool, dry, dark place away from other chemicals. Shelf life is limited. Normal pool shockers lose effectiveness over time. Therefore, it is best to use pool shockers in the order in which you purchased them and within one year.

The correct handling of pool shockers

Do not breathe air from the containers under any circumstances. Chlorine gas causes throat and lung irritation.

A respirator may be appropriate. However, for the small amount of chlorine for a private pool, this is rather not essential.

Only add the pool shocker directly to the pool water if it explicitly says so on the package. Pool shocker that is difficult to dissolve must be distributed in a bucket of water beforehand. Added directly to the pool, it would simply sink to the bottom and make the pool floor bleach and brittle.

Pool shockers are not intended for long-term storage. Before opening a new container, check to make sure there is no other open.

You have done it!

Now you are almost a real expert when it comes to pool shock chlorination. Now you just need to get started and go through everything step by step in practice.

Larry has been a true water rat since childhood. Pure pleasure turned into a passion. That's why he is the first point of contact for friends and acquaintances when it comes to pool-related problems. He is an integral part of the PoolHandbook editorial team.