Types of Chlorine For Pools

Chlorine and the use of Shock are the basic ingredients for the Control of your pool Chemistry. By mastering your pool, you will save hours of your time and countless amounts of money from failures. What kind of Chlorine do you need to get Control of your Pool?

The right Chlorine for you to use daily in your pool and for Shocking once a week, is the Chlorine that has the highest percentage of (AC)  Available Chlorine, is the Fastest Dissolving & if affected by sunlight will be Stabilized with Cyanuric Acid. 

Knowledge is key the key is knowledge. Swimming Pools aren’t complicated and the key to keeping them hasn’t changed. The one thing that’s changed is the cost of keeping them.


What is the Best Pool Chlorine?

Buy the right Chlorine and Super-Chlorinate every week and you will control your swimming pool. You will Master the Art of Keeping a Perfect Pool all through the season and keeping your wallet in your back pocket too.

There are only 5 types of Chlorine:

  1. Sodium hypochlorite
  2. Lithium hypochlorite
  3. Calcium hypochlorite
  4. Trichlor
  5. Dichlor

Sodium Hypochlorite

is liquid Chlorine. It’s between 10-12% Available Chlorine or (AC) as you might read on the label. Available Chlorine is the amount of chlorine that is used to disinfect. The strength or muscle.

Household Bleach is Sodium Hypochlorite but is only around 5% AC Available Chlorine. not very good for disinfecting the pool. It’s normally used in Industrial treatment or large pools at Amusement Parks it’s distributed by Chemical Feeders from large storage containers.

 Calcium Hypochlorite

This is the type of Chlorine that you see in tablet and granular form. Calcium Hypochlorite is approximately 40-78% AC or Available Chlorine.

This type of Chlorine is used in daily maintenance as the main way to sanitize your pool and Shock your Swimming Pool.

When you go to the store this type is the likely type of Chlorine that you will see. The only difference in the types of Calcium Chlorite Chlorine that you see will be the AC or strength of it.

 Lithium Hypochlorite 

This type of granular Chlorine is approximately 35% AC but can dissolve super fast. That makes it great for shocking in Vinyl or Fiberglass Pools. It is also good to use if there are problems with the pool having hard water. It is expensive to use and might be better to use in smaller vinyl pools.

Trichlor and Dichlor are types of Chlorine that are approximately 80-90% AC. They are also Stabilized.  Stabilized chlorine has Cyanuric Acid which acts as a type of sunblock for Chlorine. Cyanuric Acid slows the process of the sun breaking down the disinfecting powers of Chlorine.

Therefore, Dichlor and Trichlor are used in outdoor pools as pucks/tablets, sticks, and through the skimmers or through a Chemical Feeder.

Because indoor pools do not need to worry about the sun, and do not need Cyanuric Acid, There is no need to worry about this.


How to Shock Your Pool

Chlorine chemistry plays a key role in protecting and helping to keep swimming pools healthy, clean, and safe.

It safely eliminates bacteria, viruses, and parasites from water and ensures lasting disinfection during its time in the pool. When Chlorine is added to the pool for a while at the same dose, bacteria and organic material start to get resistant to its disinfecting power.

So your kids have a pool party the next day you will need to Bump the dose. That just makes sense. Right?  Even if they didn’t you should super-chlorinate every week in the summer months.

Free Chlorine or FAC is the simplest test to monitor and should be monitored every day.  Free Available Chlorine is the Chlorine that is the portion of the Chlorine that is leftover in the pool to guard against any contaminants that come their way day.

Free Chlorine levels should always be somewhere between 2-4 ppm. Never below 1.0 ppm

Combined available chlorine (CAC) or chloramines. The portion of chlorine in the water that has reacted and combined with ammonia, nitrogen-containing contaminants, and other organics such as perspiration, urine, and other swimmer waste.

Some chloramines can cause eye irritation and chlorine odors. Sound Familiar!

When you smell chlorine coming out of your pool it’s not the right type of Chlorine so you need to Bump the dose.  

Total chlorine is the sum of both the free available and combined chlorine. Total Chorine should never go less than 0.2 ppm

Superchlorination is another term that is sometimes used for shock treatment with chlorine products when 5 or more ppm of FAC is added.

This mode of shock treatment in addition to oxidizing undesired wastes is used to rid the pool of algae and bacteria that might be hiding in filters and hard-to-sanitize areas like the nooks and crannies all around the inside of your pool.

This little space is where algae and bacteria hide and colonize to where it’s starting to destroy your pool. So how do you avoid this from happening Shock Your Pool?

Shock treatment. The practice of adding significant amounts of an oxidizing chemical to the water to destroy ammonia, nitrogen-containing, and organic contaminants.

Adding chlorine as a shock treatment can also control algae and bacteria, but read the label to make sure that your product can do this.

When the swimming pool’s usage is on a different day today, the temperatures can be extreme.

Which way is the best way to add Chlorine to your swimming pool chlorine tablets or granules? Read this article on MyWaterEarth&Sky called  Chlorine Tablets vs Granules  for answers to your chlorination needs.


Depending on how hot the week has been and how many people were in the pool will determine how much shock chlorine you’ll be using at the end of the weekend or even at mid-week when your residual testing comes up low.

How many times a week you add Shock Chlorine is important, but when you add Shock Chlorine is also just as important. Read the article on MyWaterEarth&Sky called  When Should You Shock Your Pool?


The best Shock Treatment is fast-dissolving granular Chlorine that is over 70% Available Chlorine. There is a certain percentage of inert material that will find its way to the bottom of your pool. So vacuum the next morning if you can. 

Superchlorination or Shock Treatment also gets rid of chloramine odor.

Adding 10 times the level of combined chlorine or chloramines in the water achieves so-called breakpoint chlorination when there is enough extra chlorine to consume the irritating chloramines.

Once Free Chlorine Levels Start to slip, you need to shock your pool. In Fact, Super-chlorinating every week or so during the summer months is highly recommended. In order to prevent a problem, you will be able to offset a bigger problem and this is the first place where you will save money. Lots of it.

How to Add Chlorine to a Pool

  • Alkalinity is always adjusted first Keep between  80-120 ppm
  • Adjust PH after Alkalinity Keep PH between 7.2–7.8
  • Brush the walls and bottom of the pool. Vacuum organic material off the pool bottom before and after your shock. That material will kill the efficiency of the chlorine and you will add twice the amount to get the same result.
  • Make sure the eyeballs are turned down on the discharge in the pool. Kids in the pool tend to turn them up while they are playing in the pool. It provides less air contact and a better mix when they are turned completely down.
  • Buy the right kind of Chlorine. Check the label on Chlorine packages to see what’s inside. Same with Tablets. You need to see how much AC is in the chemical. Use the Buyers Guide- What Kind of Chlorine Do I Need? my article above.
  • If you are using granular Chlorine you won’t have to buy shock just super chlorinate once a week to bump your residual.  That will cut the cost.
  • Add the right Chlorine & Shock at Night for a better kill rate. Walk around the edge and broadcast the Chlorine around the Parameter of the pool. Concentrate on the deeper parts of the pool.
  • Regular maintenance will keep problems from starting. This will save money. 
  • Balance Your Pool’s Chemistry like below  1. Alkalinity 2. PH  3. Chlorine Residual



With a little bit of knowledge, you’ll know at least the basics of pool care, which will enable you to Master the Art of Pool Operator.

Chlorine is at the tip of the very basic ingredient for that success. Know your chlorine. It all starts right there. It will drive the Chemistry under the right balance to minimize any problems for the season to make you the Master of Your Swimming Pool.

Adding Chemicals to your pool should be done on some type of schedule but then there are times because of usage or work that make it impossible. In the event, of a water problem or you are just in a hurry and need to add chemicals, read the article on MyWaterEarth&Sky called  How Long Does It Take For Pool Chemicals to Work?

Jim has over 30 years in the Water/Wastewater and Water Filtration Business as an Operating-Consultant. He has written over 300 articles on the World Wide Water Situation & Solutions. He is an Inground Pool Owner for 30 years.


Author/Editor, MyWaterEarth&Sky

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