Chlorine is an effective and reliable sanitizer, disinfectant and oxidizer for swimming pools and spas. Its advantages include availability, affordability and proven effectiveness. The majority of complaints lodged against chlorine by residential pool and spa owners can be traced back to an unintentional overuse of the chemical.
The advent and spreading popularity of mineral sanitizers provides a fantastic alternative to traditional chemicals, but mineral sanitizers do not completely eliminate the need for chlorine or bromine; instead, levels are reduced 40% to 60%. While such a reduction may be great - depending on your views of chlorine, of course - pool and spa owners still need to understand the types of chlorine available to them, as well as the advantages and any special considerations associated with each type. Chlorine can be purchased in four different forms: granular, liquid, tablets, and sticks. Each delivers effective sanitization through different applications and varying levels of Available Chlorine. The deciding factor in your decision to use one type of chlorine over another should be your preference in pool maintenance habits.
No matter which method you use, add chlorine when a test reading shows Free Chlorine levels to be lower than 2.0 ppm. The ideal range for Free Chlorine is 2.0-3.0 ppm.
Granular
Advantages: Granular chlorine dissolves quickly and provides the most precise control over chlorine levels
Application: Dissolved in a bucket of water prior to being added to the pool or spa
Frequency of Application: Weekly, though possibly daily depending on bather load
Helpful Hints:
Daily chemical testing is suggested
Granular chlorine is ideal for all types of pools, though it is probably most cost-effective when used in above ground swimming pools
Never use granular chlorine in an automatic chemical feeder.
Look for a concentration of 99.5% Sodium Dichloro-S-Triazinetrione
Commonly called Dichlor
Other Notes: There are three types of granular chlorine: Calcium Hypochlorite (Cal-Hypo), Di-chlor, and Lithium Hypochlorite, with differences in pH and stability.
Calcium Hypochlorite
Cal-Hypo has larger granules and is the most affordable of the three types of granular chlorine. Because it does not contain a stabilizer to protect against chlorine loss due to UV exposure, it is ideal for use with indoor pools and spas. With 65% available chlorine, Cal-Hypo is commonly used as a shock. Its popularity is due to its widespread availability and affordable price.
Di-Chlor
Another form of granular chlorine, Di-Chlor is less harsh and has a 7 pH level. It's more stable than Cal-Hypo so it lasts longer in the water with 62% available chlorine. Although Di-Chlor is more expensive than Caly-Hypo, it leaves no dust and dissolves rapidly for safe handling and application.
Lithium Hypochlorite
Lithium Hypochlorite is the most expensive out of the three types of granular chlorine. Lithium Hypchlorite has an 11 pH level, making it necessary to add acid to your water to achieve balanced chemistry. Its super fast-absorbing property makes it safe for all types of pool liners, including vinyl. Lithium Hypochlorite is versatile enough to be used as a shock or daily sanitization. It is calcium free and doesn't affect the hardness level of your water. Lithium Hypochlorite is the safest to store because it's dust free and non-flammable.
Liquid
About: Liquid chlorine is called sodium hypochlorite, or sodium-hypo, and has a similar composition to bleach. With an available chlorine level of 10-15%, liquid chlorine is most frequently used in commercial pools.
Application: Can be added directly to swimming pool water, but it is recommended that liquid chlorine be dispersed by way of a diaphragm pump or a peristaltic pump.
Helpful Hints: Liquid chlorine is highly corrosive. Take caution when handling.
Tablets
Advantages: Tablets have the highest available chlorine at 90%. Priced similar to granular chlorine, they are ideal because they reduce maintenance for the pool owner. Available in one inch and three inch sizes.
Application: Floating dispensers and automatic chemical feeders
Frequency of application: Depends on the demand and the size of the chemical feeder. Expect tablets to last at least one week.
Helpful Hints:
Three inch tablets require less maintenance and are the most common size available.
One inch tablets dissolve more quickly than the 3" tablets and their smaller size makes them ideal for smaller swimming pools and spas.
Commonly called Trichlor
Chlorine sticks share many of the same characteristics, advantages and applications as chlorine tablets. Sticks are larger and dissolve more slowly than tablets.
