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 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 to 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 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.

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.

There are great Chlorine products right here on MyWaterEarth&Sky along with Testing and Pool & Spa Equipment

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 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

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Did you ever have a friend that before you went fishing would stop at a Bait shop and buy it out, listening to the salesman’s pitch about how he might need this or he might need that? You can’t blame the salesman that’s his job. Most people walk into a Pool Supply store are the same way. There are literally hundreds of chemicals that all do the same thing.

With a little bit of knowledge, you’ll know at least the basics of pool care, that 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.

Related Questions:

What is the safe chlorine level for swimming? Chlorine is measured by ppm, which stands for parts per million. The lowest mandatory level is 1 ppm and the maximum is 3 ppm. There a number of factor, which affect the chlorine levels of swimming pool

 What are physical hazards of chlorine? Inhalation of chlorine gas can cause difficulty breathing, chest pains, cough, eye irritation, increased heartbeat, rapid breathing, and death.

 How does calcium hardness affect pool water? The reason you balance alkalinity, pH, then calcium hardness is that adjusting alkalinity  affects pH. Adjusting  alkalinity and pH often affects your calcium hardness,


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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