Chlorine Tablets vs Granules

When the swimming pool’s usage is on a different day today, the temperatures can be extreme stressing disinfection through the summer season. What is the best way to add Chlorine to your swimming pool chlorine tablets or granules?

Granular Chlorine

Granular contains more inert Ingredients
You can adjust the amount according to Chl residual
Bump the Chl residual to create a shock effect
Save the cost of Shock Chlorine


Easy use
Won’t interfere with swimmers
Will last longer
Won’t damage the liner or pool paint
Need to Shock more


For convenience, Chlorine Tablets are easy to use and work efficiently, but can’t give you the kind of controls that Granular Chlorine can give over the maintenance of you’re swimming pool. Here are some methods using Granular Chlorine that can keep your pool smooth sailing during the dog days of summer.


What is Granular Chlorine


Granular Chlorine is made up of Calcium hypochlorite, a dry crystallized compound of chlorine, that is commercially available in dry mixtures containing up to 80% calcium hypochlorite, though 65–75% is more common and lower concentration formulations are also available.

High strength Calcium Hypochlorite has been widely used as a disinfecting agent in swimming pools and municipal water treatment since 1928.

It is a convenient source of available chlorine, one of the most widely used chemicals for disinfecting swimming pool water. A concentrated source of chlorine in solid form Provides a residual level of free available chlorine (FAC) in the pool and spa water to kill disease-causing organisms.

It acts as a sanitizer, algaecide, and/or shock product depending on the application method. It destroys contaminants in pool and spa water such as those found in sweat, urine, and windblown debris.

It does not contain a stabilizer (cyanuric acid), though it can be stabilized toward the sunlight in recreational water through the use of a chlorine stabilizer (cyanuric acid) Proper application gives excellent water clarity.

Available in slow-dissolving tablet forms or more rapidly dissolving granular forms and requires the use of some specialized storing and handling. Calcium Hypochlorite can be used as a sanitizer every day. As long as the PH is between the range of 7.2 and 7.8. When used properly, hypochlorous acid will be the direct result which will kill algae, bacteria, and other microorganisms and control the pool.

Besides being used as a sanitizer it can use as an algicide and will oxidize contaminants and chloramines. If the free chlorine levels are where they should be, the water test will be at 1.0-4.0 ppm then Hypochlorite will properly sanitize you’re pool and will kill off any populations of microorganisms that try to grow.

With Calcium, too little is not good but too much can cause some problems like cloudy water or scale formations in the water.  When using  Sodium Hypochlorite,  there may be a rise in hardness and alkalinity that causes Calcium Carbonate. You will then need the water to be balanced. The easiest way to deal with this is to empty some of the pool water. That’s it!


How To Add Chlorine Tablets To Pool


In swimming pools, chlorine tablets are used not only to kill bacteria in the water but also to prevent the growth of algae and to maintain the proper pH level. The pH level is a rating on a scale that indicates how acidic or caustic a substance is. A safe pH level for a swimming pool is between 7.2 and 7.6. The same as Granular Chlorine

Calcium Hypochlorite can also work well in spas and will sanitize at levels of 2.0-5.0 ppm. When Calcium Hypochlorite is used to disinfect pool water then .08 ppm of calcium is added every time 1.0 ppm of Free Chorine is added.

Swimming pools usually need a measurement of 150 ppm-1000 ppm of calcium Hardness in the chemistry of the water. So testing needs to be done now and again to make sure levels aren’t climbing. 

Chlorine tablets are solid pellets of a chemical compound containing chlorine that is used to disinfect and purify drinking water and water used in swimming pools. Chlorine has long been used to kill bacteria and microbes in water to make it safe. In its gaseous form, however, it is poisonous. Chlorine tablets became one of the most common methods to deliver the desired results safely.

Tablets are easy to apply to your swimming pool by just adding tablets to floaters to the water. But your pool will need to be shocked most likely weekly or even more. You have no control over the residual or when or how the sanitizer is added. Less control means more money. 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.

How to Add Granular Chlorine to Pool


Whenever you shock your pool or add chemicals empty the pool of rafts, tubes, and floats and any organic material like leaves that are on the bottom of the pool or floating on top of the water.

You don’t want to waste any of it.

  • Always add chlorine at night for the best disinfection rate and the absence of sunlight that burns Chlorine off.
  • Adjust the PH level of the pool if you need to.
  •  If you need to adjust the Ph You may also need to wait because PH will take a while for the water’s chemistry to change. It’s a slow process. You don’t want to do it too fast or you’ll be ping-ponging from PH Low to PH High and back. In order for the complete kill with any kind of chlorine you’re PH has to be right!
  • Also, keep the filter running.
  •  Use a 5-gallon bucket you can buy at Home Depot and mix a couple of scoops of approximately 2 libs of Calcium Hypochlorite with a 2/3 bucket of pool water.

It’s not an exact science. Don’t kill it, just dilute the Granular Chlorine you need according to the Chart and walk the perimeter of the pool slowly pouring the contents of the bucket a foot or so off the wall so it will have some contact.

This is a good way to deliver chlorine fast and lethal. If you have a vinyl bottom on the pool, it will keep the Granulars from laying on the bottom and damaging it.

The new Granular Calcium Hypochlorite is stronger than it used to be with up to 70% Available Chlorine and 73% Active Ingredient which is close to what a good quality Pool Shock is. It has fast-acting dissolving crystals so you won’t have to mix and dissolve it, especially in a concrete or cement pool.

You can play with numbers and use the chart as a ballpark reference guide. Apply it all at one time by broadcasting the Granular around the parameter walls of the pool. If you dilute it then cover as much of the surface as possible. But try and add it fast and all together in one shot.

If your pool was 30,000 gallons and you were using Calcium Hypochlorite with 67% Active Ingredient to “Bump” the pool to 5ppm you would have to add approximately 2 lbs of Granular Chlorine to Super chlorinate the pool water. Add it Fast. So the Pool water gets the Chlorine all together in one shot. It really is effective that way.

In a concrete or cement pool, you wouldn’t have to dilute and mix the Granular Chlorine. You can walk around the pool and broadcast the granules as you move around the perimeter walls. There is stronger “Hypo” granular chlorine available that is up to 70% available chlorine. If you experiment you can add or reduce the amount you need to “Bump” to double the Residual.

Use a reliable kit along with fresh reagents (check for expiration dates on the bottles) before Testing Pool Water.

“Bumping” You’re Pool Or Super-Chlorinating

A bump to your chlorine level is just to boost its strength and get a handle on any growing algae or if you are expecting a large crowd to use the pool.  You can use less granular chlorine during a super-chlorination or a “Bump” than if you were to Shock the pool.

The goal is double the normal residual that you normally have in your pool. Bacteria and Algae have a tendency to adjust to some chlorine residual by hiding out in cracks and crevices or underneath dead bacteria growth.  With some Brushing a few times a week along with “Bumping”  your residual will be enough to get a good kill and crystal-clean water.

You can save a lot of money by not shocking the pool every week like the Pool Store want you to do.  It’s a waste of money. It will pay off this summer. Be the Master of your Swimming Pool by controlling it with good testing and procedures. 

Total vs Free Chlorine


Free Chlorine

This is the chlorine that you test for in your swimming pool water. This type of chlorine is available to sanitize your pool.

Your pool should have between 1 and 3 parts per million (ppm) in the water.

Combined Chlorine

This is chlorine that has been used up by the disinfection process of the water. While it’s still in the water, its ability to sanitize is reduced and not as desirable to free chlorine.

Total Chlorine

This type of chlorine is the sum of both free chlorine and combined chlorine.

When you add chlorine to your pool, it reacts with the water to form hypochlorous acid and hypochlorite ions. This is desirable. These compounds together form what we call free chlorine. Once this chlorine begins to react with the contaminants in the water, such as nitrogen and ammonia, it is called combined chlorine.

In this state, chlorine isn’t as strong at cleaning compared to free chlorine as it begins to be used up. You want to make sure your free chlorine levels stay in check. This ensures the job has been done. For example, if your free chlorine levels and total chlorine levels are the same, then there’s no combined chlorine in your water.

If your total chlorine level is higher than the free chlorine level, the difference between the two is the combined chlorine level. To make sure your pool is sanitized, your free chlorine should remain higher than your combined chlorine.

Subtracting Free chlorine from Total chlorine will give the level of Combined chlorine in the pool water. When combined chlorine (chloramines) are 0.3 ppm or greater, Then that is when you consider Shocking the pool.

Knowing the difference between the Chlorine residuals and how one affects the other, can result in you gaining more information and keeping your pool under your thumb for constant control.

Using Granular Chlorine instead of Chlorine Tablets with the “Bumping” technique is a little more hands-on and just a little more work, but in the end, it will save you money and give you another formula for being the Master of your Pool.


For more great information on fine-tuning your pool this coming season like this one just stay right here at MyWaterEarth&Sky-normally pools see a ¼ – ½ inch loss of water per day due to evaporation. This is roughly 2 – 4 inches per week. For a normal-sized Inground Pool, …………………………… Continue reading



JimGalloway Author/Editor



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