HomeWorks: Using Pool Chlorine

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Chlorine is a popular chemical used as both an oxidizer and a sanitizer. All forms—tablet, liquid, and powder—are usually inexpensive and last a month per average package. Unlike many pool chemicals, chlorine immediately goes to work, ridding pool water of cloudiness and bacteria. Such a fast reaction means pool water can look clean in hours and stay that way for a long time.

What is Chlorine and Why it's Important

A certain amount of chlorine solution should remain in pool water in order to destroy any harmful material that develops. There are two types of chlorine present in the water at any given time. The first type, free available chlorine (FAC), acts as a standby to clean up the water when needed. Combined available chlorine (CAC), the second type, is made up of nitrogen compounds and has combined with organic material and serves no positive purpose.

CAC has a noticeable odor, which alerts the user there is not enough FAC in the pool. When you smell the odor, you smell actual chlorine. Therefore, FAC is considered the good type since it actively cleans the water. Both the FAC and CAC make up what is commonly refereed to as total available chlorine.

Different Forms of Chlorine

Chlorine is available in three main forms—liquid, table, and granular powder. Some of the selections contain more chlorine than others. Some may also come with stabilizing formulas that help the chlorine keep its strength in heat and ultraviolet exposure. Products containing the highest amount of free chlorine usually cost the most, but are more stable.

Sodium hypochlorite, the liquid form, contains about 15 percent of free chlorine. Still, it is very unstable. Calcium hypochlorite is the granular form of chlorine. It contains roughly 65 percent free chlorine and dissolves very quickly. It is more stable, but is best used with a sanitizer solution. Dichlor is the tabular type that dissolves quickly in water while trichlor dissolves slowly. The latter contains 90 percent free chlorine and is the most stable. Dichlor only contains about 60 percent free chlorine.

Adding Chlorine to Pool Water

Administering chlorine is not as simple as just dumping a cup full of product in the pool. For instance, granular and liquid chlorine should be mixed with water prior to placement in the pool. The two can easily stain vinyl pool liners and cause irreversible damage. Always use a clean container when adding chlorine solution to a pool. Tablet forms on the other hand are easier to administer because they can be placed in an erosion feeder or the pool skimmer to dissolve.

A more expensive yet less maintenance-inducing option is to install a chlorine generator. The generator passes a current through water that turns salt to chlorine. Remember salt is composed of sodium (Na) and chlorine (Cl). All the owner has to do is replenish the salt level a few times during the season (as recommended by the manufacturer).

Maintaining the Efficiency of Chlorine Use

Chlorine levels in most pools need to be between 1 and 3 parts per million (ppm). Heat and the sun’s ultraviolet rays can make chlorine unstable and reacting improperly. Stabilized chlorine tablets are the best product to use if located in warmer climates. This will help improve the life of the chlorine and save you money.

Never mix pool chemicals together as this may cause a bad reaction or damage the pool liner. Always keep chlorine and similar pool treatment chemicals away from children and in a cool, dry location. Most importantly, follow label directions on the side of each chlorine container. Following directions in administering chlorine can help make your pool a safe and healthy place to relax.