Swimming Pool Chlorine Buyer’s Guide

chlorine-tablets-sinkingChlorine is one of the most widely used chemicals in the world. In addition to playing a critical role in production of plastics and polymers, chlorine is used for bleaching, disinfection of drinking water and in swimming pools to help keep the water clean and safe by killing bacteria, germs, and algae.

Today’s topic is to explain two different types of chlorine for pools and when to use each chlorine type.

TABLET CHLORINE: For daily chlorination, a slow dissolving tablet is best to prevent peaks and valleys in your chlorine levels. Chlorine tablets are also stabilized – which means they are protected from the UV rays of the sun. Tablets or sticks gradually release chlorine, without dust or binders, and it helps balance your pH levels due to it’s nearly neutral pH.

In The Swim Chlorine Tablets

3-inch-tabletsThe most popular type of chlorine for everyday pool use is Trichlor-S-Triazinetrione, otherwise known as trichlor chlorine tablets or sticks.

And the most popular brand for pool chlorine tablets in America is In The Swim. Our chlorine tablets are made with nearly pure, 99% Trichlor, with 90% active available chlorine. They are slow dissolving, with no oily binders or residue.

Triple Action Tabs

triple action tabsTriple Action Tabs are made of Trichlor, but in a 72% available formula, due to the additional two ingredients added by Dr. Pool. He mixed clarifiers and algaecides in his trichlor formula, for a triple-action chlorine tablet!

In addition to sanitizing the water, these chlorine tablets will prevent algae growth and clarify the water. They make pool maintenance faster, more convenient, and even add sparkle to the pool!

Chlorine Tablets or Sticks?

3 inch jumbo chlorine-tabletsOther than the size and shape, there is no difference between trichlor tablets and sticks. The chunky sticks are about an ounce heavier than the 7 oz chlorine tablets and are 4 inches long. chlorine-sticks

We also sell one inch tablets, which dissolve more rapidly for high use pools. All three sizes of trichlor contain 90% available chlorine. The three inch tablets are our most popular and economical chlorine option.

We also sell 1″ & 2-5/8″ Cal Hypo tablets. These are used by commercial pools or indoor pools, or anyone who wants to use an unstabilized tablet. A Cal Hypo feeder is required, Cal Hypo tabs cannot be used in a Trichlor feeder.

How to Dispense Chlorine?

Trichlor sticks or tablets can be placed in a chemical floater which simply floats around the pool. The better option would be a Tri-chlor chemical feeder, installed on the return line pipe. The rate of distribution can be adjusted based on the needs of your pool.

hayward automatic chlorinatorpool-floaterChemical feeders can hold over twenty 3 inch tablets, whereas chlorine floaters can only hold about 5 or 6 tablets. If you are like me and forget to check the floater every few days, look at installing a new Hayward automatic feeder. Then just fill it every 2-4 weeks, to maintain a steady flow of chlorine to your pool.

POOL SHOCK: The second type of chlorine to discuss is for shock treatment and/or algae removal. These types of chlorine will sanitize the water and destroy bacteria, break down contaminants and help prevent algae growth. They also break apart chloramine bonds, which give the water a strong chlorine odor.

Granular Pool Shock

  • chlorinating-granulesThe granular form of chlorine is known as Sodium Dichloro-S-Triazinetrione, in simpler terms, Di-Chlor.
  • The benefit of using granular chlorine is it is fast to dissolve and there is no pH change. It’s also the only stabilized form of pool shock, protected from UV rays.
  • The downfall to this product is it can burn a hole in your pocket very quickly if used as daily chlorination. Di-Chlor is better as a shock.

Instant Liquid Chlorine

  • instant-liquid-chlorine-With 73% available chlorine, this product comes in a granular form that quickly dissolves when added to your pool. Simply pour this in front of your return line.
  • Be aware that Liquid Chlorine has a high pH and rapidly dissipates in an unstabilized pool.
  • The benefit of using this form of chlorine is it is safer and easier to use. Secondly, you do not need to utilize a floating chlorinator or an automatic feeder to dispense the product.

Calcium Hypochlorite

  • swimming pool shock, in a powdered form, 1lb bagCalcium Hypochlorite, otherwise known to us as Cal Hypo, has 68% available chlorine and has a slightly higher pH level.
  • The benefit to using this product is this can be used for daily chlorination and shocking the pool as well.
  • The downfall to cal hypo is it rapidly dissipates in the sun, adds calcium to the pool, and must be pre-dissolved for vinyl pools.

Chlorine Free Pool Shock

  • chlorine-free-shock--Can this be used in a chlorine or bromine pool? Yes, it will sanitize and purify just like a chlorine oxidizer.
  • Chlorine Free Shock kills with the power of oxygen and leaves no dust or residue after shocking.
  • No chlorine smell and no pre-dissolve needed. By using chlorine free shock, no risk of damaging your liner, and you can swim immediately, no waiting for chlorine to dissipate.

Assure Multi Shock

  • assure-multi-shockThis is made up of 58% sodium dicholoro-s-triazinetrione, aka Dichlor.
  • Why use it? This product does not affect pH levels or cause cloudiness.
    Assure dissolves almost instantly and you can swim as soon as 15 minutes after use.
  • Assure Multi Shock works as a disinfectant, controls algae growth, contains a clarifier, and enhances water quality.


  • cal-chlorCal-Chlor is 68% available chlorine and 35% calcium. This product is the same as our In the Swim pool shock, but in a bucket.
  • Pre-dissolve to prevent bleaching of a liner.
  • This is a non-stabilized product, so best to be added at night when possible, or in a stabilized pool.

The bottom line…

When choosing a chlorine product to use, determine what is best for you.  Keep in mind where the pool is located as well as the need to keep your chlorine levels between 1-3 ppm. Maintaining this proper level will ensure that you have a clean and safe pool to swim in.

If you have questions about what product is best for you, feel free to give us a call at 800-288-7946 or email drpool@intheswim.com – he loves chlorine questions!




Kristine Malak
InTheSwim Staff Blogger


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