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Introduction To Chlorine Sanitizing

Mastering the knack of pool science is not difficult with the right information and a little diligence. As for those readers who are experienced poolside chemists, put this article in the hands of anyone learning the ropes.

Think of the perfect swimming pool and visions of sparkling water and happy swimmers likely dance in your head. Keeping this scene intact involves taking the proper steps to sanitize the pool and prevent any health or aesthetic problems. The water will then remain clear of algae, free of disease causing pathogens and users won't complain about red eyes or chlorine smell.

Because you use chlorine, whether you're responsible for running a public facility or a water park, you have the necessary tools to make your job easier. For general pool treatment, chlorine has three essential characteristics: it acts as a rapid and persistent sanitizer, an effective algaecide and a strong oxidizer of undesired contaminants.

Understanding the role of chlorine in maintaining safe water is not difficult once you learn the basics of pool chemistry.


Chlorine is regularly fed into the pool water and should be tested daily -- at a minimum -- for proper disinfection. Routine chlorination kills harmful microorganisms that can cause health-related problems, such as gastroenteritis, Legionnaires disease, ear infections and athlete's foot. Learning how to properly test your water will allow you to identify the chlorine residual and demand in pool water. More frequent testing is needed if there is heavy bather use.

Listed below are some helpful definitions that will assist you in understanding the terms and tasks of applying chlorine-based sanitizers.

* Free available chlorine (FAC). The portion of the total chlorine remaining in chlorinated water that has not reacted with contaminants -- and is "free" to go to work to kill bacteria and other contaminants. Make sure your test kit can measure FAC; many only test for total chlorine.
* 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.
* Total chlorine. The sum of both the free available and combined chlorines.
* Forms of chlorine commonly used in commercial pools. Pools are treated with chlorine gas, sodium hypochlorite (liquid bleach), calcium hypochlorite (granular or tablet), lithium hypochlorite or chlorinated isocyanurates. When any of these compounds contact water, they release hypochlorous acid (HOCl), the active sanitizing agent. Chlorinated isocyanurates, a family of chemical compounds such as sodium dichloroisocyanurate and trichloroisocyanurate, also add cyanuric acid or stabilizer. A stabilizer, which can also be added separately, helps reduce excess loss of chlorine in water due to the ultraviolet rays of the sun.
* Parts per million (ppm). Measurement that indicates the parts of a substance, such as chlorine, by weight in relation to one million parts by volume of pool water. A rule of thumb to follow to maintain good water quality in pools is to keep FAC levels between 2.0 and 4.0 ppm. (see NSPI recommendation chart)
* Shock treatment. The practice of adding significant amounts of an oxidizing chemical to 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.


Carefully read and follow the manufacturer's instructions printed on the chlorine treatment package. Test the water regularly - it's a simple process to use a test kit. You want to maintain water balance by measuring:

* Free available chlorine (FAC), which should be in the range of 2 - 4 ppm, but never fall below 1.0 ppm
* Total chlorine, to assure that combined available chlorine (CAC) levels are less than 0.2 ppm
* The pH level to keep it between 7.2 and 7.8, indicating that the chlorine is working effectively
* Total alkalinity to make sure that pH levels stay steady
* Calcium hardness to protect pool surfaces from corrosion.


The guidelines set by The Association of Pool & Spa Professionals are widely used, but to be certain, you should also check the health codes of the jurisdiction where you live. The chemicals a pool needs to maintain the required standards differ from pool to pool - and day to day. Keeping records to "get to know" a pool can help you interpret its characteristics and perform the correct task.


Contrary to what most people think, a strong chlorine smell is not an indication of too much chlorine in the pool but actually a red flag that a "super dose" may be required to correct the problem.

Shock treatment adds a larger than normal amount of oxidizing chemicals to pool water. This additional dose destroys organic contaminants and oxidizes ammonia and nitrogen compounds to rid the area of irritating chloramine odor and, if chlorine is used for the purpose, to sanitize the water. Many chlorine shock products also provide usage instructions for destroying algae and bacteria, which can be an added benefit. Shocking should be done with the pump and filter operating, but after sundown to avoid the loss of chlorine to the sun's ultraviolet (UV) rays.

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. Superchlorination 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.

According to NSPI standards for public pools, the ideal frequency for a super dose is every week, depending on use and water temperature. For high use pools, superchlorination may be required three times a week or more as a preventive measure. NSPI also suggests that a good indicator of the need for a super dose is when combined chlorine climbs near or above 0.2 ppm.


As you learn your way around the pump room, you'll appreciate chlorine's importance in contributing to safe, clean water - making those visions of swimming in a sparkling, clear pool a reality.

Basic Rules of Thumb

* Always read and follow the manufacturer's instructions.
* Store chemicals in a cool, dry and shaded place.
* Never mix different types of chlorine - add each to the pool separately.
* Never mix chemicals together - add each to the pool separately.
* Avoid breathing fumes or vapors.
* Don't buy more pool chemicals than you'll use in a season - they lose effectiveness over time.
* Make sure pool chemicals are inaccessible to children.

Cost-Savers Tip

Save on chemical costs by adding chlorine for shock treatment after dark - during the day some will be lost to sunlight.

Late Summer Tips for the Backyard Gardener

For home gardeners, late summer brings a happy burst of activity around the fruits—and vegetables—of their summer labor. Many gardeners are canning and storing foods to prolong the enjoyment of their home-grown staples. Others are preparing the garden for a fall crop. The cooler temperatures of late summer and early fall can be reinvigorating to those inclined to the outdoors, and for the industrious gardener, there always seems to be one more chore to do.

While we go about these satisfying seasonal tasks, it’s good to be mindful of a handy tool that, used judiciously, can increase our success and enjoyment of the backyard, the garden and its bounty. It’s a tool that’s found in many home laundry rooms—an old standby—chlorine bleach*. Bleach is a great example of “chemistry in a bottle.” Bleach destroys disease-causing microorganisms, such as bacteria, on surfaces by collapsing essential proteins in their cells. For that reason, many people use diluted bleach solutions in the home to control germs in the kitchen and bathroom as well as high-touch areas, like railings and door knobs, during flu season. But while it’s still harvest season and we’re still enjoying the backyard and garden, here are a few lesser known but useful tips for using chlorine bleach:

* Disinfect garden tools and shears to help avoid spreading plant diseases: Soak tools in a solution of 9 parts warm water to 1 part chlorine bleach. Rinse, dry and oil to prevent corrosion.

* Disinfect terra cotta pots and saucers between plantings to help avoid spreading plant diseases: After removing all soil and plant debris and washing, soak pots and saucers in a solution of 9 parts warm water to 1 part chlorine bleach. Rinse and allow to dry.

* Before canning summer fruits and vegetables, clean then disinfect all kitchen work surfaces with a solution of ½ gallon of water + ½ tbsp. of chlorine bleach.

* Cut flowers last longer when ¼ tsp. of chlorine bleach is added to each quart of water in a vase.

* Disinfection is for the birds too: Clean and disinfect feeders once or twice per month. Immerse an empty, cleaned feeder for 2-3 minutes in a solution of 1 part chlorine bleach and 9 parts water. Allow the feeder to air dry.

* Our feathered friends need clean drinking water too: Once every two weeks, scrub bird baths with dish detergent, rinse, then fill with a solution of 1 part chlorine and 9 parts water. Let stand for 2-3 minutes. Pour it out and allow to air dry, then rinse it well and air dry again.

Here’s to a happy and productive fall!

*Always keep chlorine bleach out of the reach of children and pets.

Water Storage Tips To Assist In Emergency Preparedness

The Water Quality & Health Council offers important tips for storing water to help families and individuals prepare for emergency situations. In addition to ensuring safe water during periods of elevated terrorist alerts, home water storage is an important measure in preparing for natural disasters, such as floods, hurricanes and ice storms.

While many individuals rush to purchase bottled or distilled water during times of crises, another viable option for securing a supply of safe water is the storage of tap water for future use. Following are easy-to-implement guidelines to ensure that tap water remains potable while in storage:

Store at least one gallon of water per person, per day in a cool, dark place.

The average individual must drink at least two quarts of water every day. Children, nursing mothers, the elderly and people in warmer climates need more. Additional water should be reserved for personal hygiene and food preparation. The U.S. Department of Homeland Security encourages individuals to store enough water to last a minimum of three days - bearing in mind that water is needed for drinking as well as for personal hygiene. Water should be collected on days when it appears free of sediment or color. On certain days, particularly after a hard rain or heavy snowmelt, some tap water may have a brownish color and contain sediment.

Choose appropriate containers for water storage; disinfect before use.

Clear food-grade plastic containers, such as soft drink bottles, are ideal. Other options include fiberglass or enamel-lined metal containers. Never use a container that has previously held toxic substances. Containers for water should be rinsed with a diluted chlorine bleach solution (one part bleach to ten parts water) before use.

If necessary, treat water with a chlorine bleach solution prior to storage to prevent buildup of harmful bacteria or pathogens. Replace water every six months.

If your water is treated commercially by a water utility, it is not necessary to treat water before storing it. If you have a well or public water that has not been treated, disinfect the water prior to storage using liquid household bleach containing 5.25 percent sodium hypochlorite. Do not use scented or color-safe bleaches or bleaches containing soaps. The American Red Cross and the U.S. Federal Emergency Management Agency recommend the following procedure for treating water for storage:

* Add six drops (1/8 teaspoon) of unscented bleach per gallon of water.
* Stir and let stand for 30 minutes.
* If the water does not taste and smell of chlorine after 30 minutes, add another dose of 1/8 teaspoon and let stand another 15 minutes.
* Seal the containers and label with contents and date of preparation.

Identify additional sources of water.

In addition to stored water, other sources include melted ice cubes, water drained from the water heater faucet (if the water heater has not been damaged), water dipped from the flush tanks (not the bowls) of home toilets, and liquids from canned goods such as fruit and vegetable juices. Unsafe water sources include radiators, hot water boilers, waterbeds, and swimming pools and spas.

Emergency Disinfection of Drinking Water

When the home water supply is interrupted by natural or other forms of disaster, you can obtain limited amounts of water by draining your hot water tank or melting ice cubes. In most cases, well water is the preferred source of drinking water. If it is not available and river or lake water must be used, avoid sources containing floating material and water with a dark color or an odor.

When emergency disinfection is necessary, examine the physical condition of the water. Disinfectants are less effective in cloudy water. Filter murky or colored water through clean cloths or allow it to settle, and draw off the clean water for disinfection. Water prepared for disinfection should be stored only in clean, tightly covered, containers, not subject to corrosion.

There are two general methods by which small quantities of water can be effectively disinfected. One method is boiling. It is the most positive method by which water can be made bacterially safe to drink. Another method is chemical treatment. If applied with care, certain chemicals will make most water free from harmful or pathogenic organisms.


Boiling: Vigorous boiling for one minute will kill any disease-causing microorganisms present in water. The flat taste of boiled water can be improved by pouring it back and forth from one container to another (called aeration), by allowing it to stand for a few hours, or by adding a small pinch of salt for each quart of water boiled.

Chemical treatment: When boiling is not practical, chemical disinfection should be used. The two chemicals commonly used are chlorine and iodine.

Chlorine Methods:

Chlorine Bleach: Common household bleach contains a chlorine compound that will disinfect water. The procedure to be followed is usually written on the label. When the necessary procedure is not given, find the percentage of available chlorine on the label and use the information in the following tabulation as a guide.

Available Chlorine




Drops per quart of clear water




(If strength is unknown, add ten drops per quart of water. Double amount of chlorine for cloudy or colored water)

The treated water should be mixed thoroughly and allowed to stand for 30 minutes. The water should have a slight chlorine odor; if not, repeat the dosage and allow the water to stand for an additional 15 minutes. If the treated water has too strong a chlorine taste, it can be made more pleasing by allowing the water to stand exposed to the air for a few hours or by pouring it from one clean container to another several times.


Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately 1/4 ounce) for each two gallons of water. The mixture will produce a stock chlorine solution of approximately 500 mg/L, since the calcium hypochlorite has an available chlorine equal to 70 percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 oz.) of stock chlorine to each 12.5 gallons of water to be disinfected. To remove any objectionable chlorine odor, aerate the water as described above.


Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased in a commercially prepared form. These tablets are available from drug and sporting goods stores and should be used as stated in the instructions. When instructions are not available, use one tablet for each quart of water to be purified.

Iodine Methods -- The use of iodine as a means of disinfection may not be effective in guarding against exposure to Giardia or Cryptosporidium. Therefore, iodine use should be limited to the disinfection of well water (as opposed to surface water sources such as rivers, lakes, and springs), because well water is unlikely to contain these disease causing organisms.


Common household iodine from the medicine chest or first aid kit may be used to disinfect water. Add five drops of 2 percent United States Pharmacopeia (U.S.P.) Tincture of iodine to each quart of clear water. For cloudy water add ten drops and let the solution stand for at least 30 minutes.


Commercially prepared iodine tablets containing the necessary dosage for drinking water disinfection can be purchased at drug and sporting goods stores. They should be used as stated. When instructions are not available, use one tablet for each quart of water to be purified.