Having a private swimming pool is a luxury that makes spending time in the summer sun as well as entertaining guests outdoors a lot more enjoyable. However, with great luxury comes great responsibility as well (yes, we borrowed that from Spiderman).

Swimming pool maintenance involves a fair amount of effort from the pool owner, and an important part of that pool care is shocking your pool every now and then. We’re going to give you the lowdown on what pool shock treatment is, the different types of pool shock treatments, and more.

What is pool shock treatment?

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We all know that a lot of swimming pools use chlorine. Now, when we use these pools, the chlorine mixes with nitrogen from our sweat, urine, and body oils, resulting in the formation of chloramines.

Pool shock treatment, or super shocking a pool, involves adding a powdered form of chlorine, called a granular oxidizer, to the pool water periodically to get rid of the chloramines. Chloramines are what give you the “red-eye” after you swim, and are responsible for the strong smell of chlorine you get from some swimming pools.

There are other benefits of shocking a pool as well. Here are some of them.

Removal of algae and bacteria

The growth of algae in pool water can be controlled by using an algaecide, but if you want to actually kill and permanently remove algae, nothing works as well as a chlorine shock does.

Keep in mind that the pH level of the water has to be in the 7.1 to 7.3 range for the chlorine shock to be effective. You can also add other chlorine accelerators such as Yellow Out to help the chlorine fight algae blooms more efficiently.

Similarly, swimming pool water is also full of different types of bacteria, some of which are pathogenic while others are harmless. Shocking the pool can kill bacteria as well as bather waste such as skin, hair, lotions, soaps, urine, sweat, and more.

Before and after the swimming season

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Winterized pools are shocked before being used for the first time after the winter. This is done to clear out the contaminants from the water, make sure it is not ready, and balance it before it is used.

Bromide spas

Bromide-treated spas and pools use chlorine shocks to activate bromide ions in the water. 

After heavy rains

Heavy rains and storms wash a lot of debris including pollutants, mud, pollen, dust, and algae spores. All of this also discolors the water. To safely swim in your pool after a storm, it is recommended that you shock it before use. 

Read more: Turn off pool pump when raining

Different types of chlorine

Understanding the four types of chlorine that affect your pool water is important before you shock your pool. 

  • Free chlorine (FC) refers to the amount of chlorine actively cleaning your pool water. Your pool water FC level ought to be between 1 and 3 ppm (parts per million) for the chemical to be effective.
  • Combined chlorine (CC) refers to the amount of chlorine that is still in the water but does not have the power to clean it anymore. Ideally, this should not be more than 0.2 ppm.
  • Water testing kits are used to find out the total chlorine (TC) in your pool water, which is the sum of FC and CC.
  • Breakpoint chlorination is when you have enough FC, or ten times the amount of CC, to shatter the chemical bonds of chloramine. 

Ideally, a breakpoint ought to be reached every time your pool is shocked. If this does not happen, the chloramine count will keep increasing, forcing you to change the water in the pool after a period of time.

How often should a pool be shocked?

There is no hard and fast rule as to how often a pool ought to be shocked. You could shock your pool whenever you feel algae has been blooming too much, or use a test kit and find out the level of chloramines in the water to help you decide. 

However, since bodily contaminants and bacteria cannot be seen, a lot of pool owners shock their pools every three or four weeks just to keep them safe and sanitary.

It is also advisable to shock your pool if you’ve had more than 10-12 people have used it in a day.

What is used to shock swimming pools?

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Let’s look at what pool chemicals are used to shock pools.

Calcium hypochlorite

Calcium hypochlorite, or cal hypo as it’s popularly known, has been around since 1928. It is the most widely used pool shocker and is also used to disinfect municipal water sources.

Most commercially available versions of cal hypo contain between 65% and 75% of chlorine. This chemical must be dissolved before being used, and should not be used in direct sunlight, which is why experts advise that you use this to shock your pool only after dusk.

Once your pool has been shocked using cal hypo, you need to wait at least eight hours before you can safely swim in it. A popular brand of this chemical is Shock Xtrablue.

A word of caution though. This chemical adds around 0.8 ppm of calcium to your pool water, so please check the calcium level in your pool water before using this.

Read more: Clean calcium buildup in showers

Lithium hypochlorite

Lithium hypochlorite is a pool shocker that is best suited if the calcium content in your pool water is high. Commercial versions of this contain 35% sodium, and the material can be added directly into your swimming pool without being dissolved beforehand.

As with calcium hypochlorite, dusk is the best time to introduce this material to the pool water, and you will need to wait at least 8 hours before you can safely use the pool.

However, lithium hypochlorite is harder to find and more expensive, largely because of the demand for lithium in the battery industry. It is also worth noting that the chemical is dangerous to aquatic life, and is an algaecide. Special care must be taken while disposing of recently treated water.

Read more: Why is my pool cloudy

Sodium dichlor

Sodium dichlor is also known as dichlor or dichloroisocyanuric acid. Dichlor is really easy to use and can even be used to shock saltwater pools. In fact, it can be used for regular chlorine treatment instead of chlorine tablets and to shock the pool.

The chlorine content in this chemical is between 50% to 60%, and can, in most cases, be added directly to the pool.

Once again, dusk is when you shock the pool and you must wait at least 8 hours before it is safe for you to swim. Every single ppm of FC added using this also adds 0.9 ppm of cyanuric acid to the water.

Read more: How to acid wash a pool

Potassium peroxymonosulfate

Potassium peroxymonosulfate is commonly known as non-chlorine shock, and as the name suggests, is a chemical that can shock your pool without any chlorine.

Non-chlorine shock can be used at any time of the day, and you can swim in your pool 15 minutes after using it. However, because it is chlorine-free, it won’t prevent algae growth. 

The correct way to shock a pool

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Once you learn the correct way to go about shocking a pool, you’ll realize it’s not so difficult after all. And remember, the process remains the same whether your pool is an indoor pool, an above-ground pool, an in-ground pool, or even an inflatable one.

  • Always wait till the sun goes down to use chlorinated pool shockers. This is because the sun’s UV rays burn unstabilized chlorine.
  • Use chemical protective gloves, full-length pants, covered shoes, and eye protection.
  • Use a pool calculator to figure out the pool’s volume.
  • Run tests to find out the pH level of the water, the calcium content, 
  • Use the instructions provided by the manufacturer on the box to find out the quantity of shock needed for a pool the size of yours. Once you know, follow the instructions and dissolve the chemical in water. The usual process followed is to mix the shocker in ¾ a bucket of water and keep stirring it until you manage to dissolve most of it.
  • Add it to the water until you reach the calculated breakpoint. This will be more effective if the pool filter and pool pump are running. Then, wait for the stipulated amount of time before using your pool.

Read more: How to reduce water level in pools


We’re going to leave you with some safety tips that you need to follow while shocking your pool.

  • Never introduce the shock to the pool via the pool chlorinator. A dangerous gas will form that could make the chlorinator explode.
  • Always wear protective eyewear and chemical protective gloves while handling chlorine. You do not want to risk your eyes or skin being irritated by the fumes.
  • Similarly, never inhale the fumes from the shock containers. You could cause inflammation in your lungs.
  • Mixing different pool shocks can lead to violent reactions, and should be avoided.
What is pool shock treatment and why is it important? was last modified: November 11th, 2022 by Narayan Shrouthy
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Are you telling me that the irritant in the water is not the chlorine? Is it the pee?