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Sanitizers
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Introduction to OxidizersAlmost all swimming pools and spas in Canada and the United States are disinfected by chlorine or bromine in one form or another. There are no fewer than six types of chlorine and two kinds of bromine compounds generally available. Each one has its own characteristics. Our purpose is to review each of the types of chlorine, bromine and permonosulfate compounds and to discuss the advantages and disadvantages; cost rating and hidden costs; safety; and tips for use as a pool or spa water disinfectant and or oxidizer. Before we can effectively discuss oxidizers, sanitizers and disinfectants we need to define what oxidation means and explain the difference between oxidization, disinfection, sanitization, superchlorination and shocking. Disinfection originally meant ridding a person or place of an infection or an infectious disease As a medical term, the destruction of disinfection means the germs of disease In swimming pool and spa water, disinfection means the killing of all the pathogenic (disease-causing) organisms in the water. The active forms of chlorine and bromine are two of the more common types of disinfectants. Sanitation means rendering sanitary or killing living things. Sanitation is like a step better than disinfection. You may want to think of it as you would the word sterilization. In swimming pool and spa water, sanitation means the killing of all bacteria and algae. plus any other life forms in the water -- disease-causing or not. Oxidization means the ridding from pool or spa water of ammonia and nitrogen compounds. Originally, oxidation referred to a chemical reaction in which oxygen combines with another substance. Its usage has long been broadened to include any reaction in which electrons are transferred. Oxidation and another chemical reaction called Reduction always occur at the same time. The substance that gains the electrons is called the oxidizing agent. An oxidizing material is any chemical or compound that spontaneously evolves oxygen. It may be helpful if you think of oxidization as a powerful chemical reaction that "bums up" organic matter ·(usually swimmer and bather waste) in the water. Four additional terms are used to describe some chemical oxidizing compounds in our industry. They are algaecide, bactericide, algistat and bacteriostat. Superchlorination is an easy one and the one you are most familiar with. It means the addition of enough chlorine to the water to kill all living things (sanitation) and to destroy any organic wastes -- ammonia and nitrogen compounds -- present in the water (oxidation). The terms "superchlorination" and "shock treating" or "shocking" used to mean the same thing. However, because of some new-to-our-industry chemical compounds, the two terms now have different meanings. "Shock treating or shocking" has come to mean adding anything to the water that will remove or destroy ammonia and nitrogen compounds. Chlorine is but one of the chemicals that can this be used for this purpose. Nonchlorine shock treatment, also known as permonosulfate compounds, also can be used to oxidize organic wastes. Some chemicals can perform all of the things we have described. For example, chlorine in the right concentration can disinfect, sanitize and oxidize. It also is an algaecide, an algistat and a bacteriostat, it is a superchlorinator and a shock treatment.
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Introduction to ChlorinesDue to numerous brand names available, we opted to use the chemical name of the six basic types of chlorine. Since all chlorine products are required by law to display on the label, their chemical name and concentration, it shouldn't be too difficult for you to identify the different chemicals by brand name. Our purpose is to review each of the types of chlorine and to discuss the advantages and disadvantages; cost rating and hidden costs; safety; and tips for use as a pool or spa water disinfectant and oxidizer. Some things you should note that are not listed in with the types of chlorine below are; When chlorine in its various forms is added to the water it produces hypochlorous acid. At a pH of 7.5 the amount of hypochlorous acid produced is about 50%. This is the chemical species that controls bacteria and algae and oxidizes organics. In fact, all pool chlorines once dissolved produce this common product. Therefore if one understands the chemistry of hypochlorous acid, then one will understand the chemistry of all six chlorine products once they are dissolved in the water. Lets take a closer look at the part of chlorine the does all the work, "hypochlorous acid" (HOCl). In chemistry there are strong acids and weak acids. While some strong acids can do meaningful damage to human tissue, weak acids are relatively harmless. Citric acid (found in lemons and oranges) and acetic acid in vinegar are examples of weak acids. Hypochlorous acid falls under the weak acid category as well. There are four main reactions of hypochlorous acid that affect pool and spa
sanitation; 1) the dissociation (break up) of HOCl . 2) reaction of bacteria and
organics. 3) reaction with ammonia (NH3). 4)reaction with sunlight.
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Gas ChlorineIf cost were the only consideration, gas chlorine (liquefied chlorine gas, chemical formula Cl2) would be the hands-down winner. However, most people or even service technicians would rather not be anywhere near gas chlorine, whether it is cheap or not. So there must be factors other than cost to consider in making your buying decision -- things like water quality; understanding the product; how the product fits with your water-treatment program; ease of use; safety; availability; storage, handling; previous experience, and so forth. Gas chlorine is the purest form of chlorine you can buy. There are no fillers or carriers, so all the chlorine you add to the pool water is used for disinfecting, sanitizing and oxidizing. Gas chlorine is the least expensive type of chlorine to buy. But it also is the most dangerous to use and store and is subject to the largest amount of government regulation. The operator/technician (applicator) must be registered by the Federal Environmental Protection Agency (EPA) as an applicator and repackager of chlorine. The Federal Department of Transportation (WT) has specific regulations for transporting gas chlorine. In addition, many state and local agencies -- the California Highway Patrol, for example -require permits for carrying gas chlorine on or in your vehicle. You also will need special racks and locking devices on your vehicle and special regulators and scales to weigh the amount used. chlorine causes a very acidic condition to occur in the pool -- that is, it drastically lowers the pH. It is therefore necessary to add about 1.5 pounds of soda ash or 2 pounds of sodium carbonate for each pound of gas used. Because gas chlorine does not have cyanuric acid (conditioner) in it, you must use cyanuric acid separately to keep the chlorine in the pool from being degraded by sunlight.
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Liquid ChlorineLiquid chlorine (sodium hypochlorite, chemical formula NaOCl) is manufactured by bubbling chlorine gas through a solution of caustic soda. The resulting liquid yields 15-percent available chlorine, but the concentration is very unstable, and within two weeks, the available-chlorine level will drop to approximately 12.5 percent. Within 30 days, during the summer, it will drop to 10 percent. Fortunately, the process slows down or stops at around 9 percent. At l0-percent concentration, one gallon of liquid chlorine contains about one pound of available chlorine. Because it does not have to dissolve, liquid chlorine makes hypochlorous acid (the killing form of chlorine) instantly when added to water. It can be used for regular or superchlorination. Liquid chlorine is non-flammable and is compatible with other water-treating chemicals commonly found in a pool or hot tub. Use and storage of liquid chlorine can have a great effect on its available chlorine level. Liquid chlorine should be stored in a cool place, shaded from sunlight. The available-chlorine level in a jug of liquid chlorine will go from more than 12 percent to 9 percent in one day if it is sunny and the temperature gets up to 105' F If it gets to 120' F (which it sometimes does in the back of a service truck), the available chlorine level can go from 12 percent to 9 percent in just 2 hours. Believe it or not, the way you pour liquid chlorine into the pool can affect its available-chlorine level. It should be poured into the pool with the jug as close to the water surface as possible. Aeration and sunlight can destroy part of the available chlorine on the short distance between the mouth of the bottle and the water surface. In fact, 1 to 2 percent of the available chlorine can be lost by pouring the liquid from only 4 feet above the water's surface on a sunny, hot day. The equipment should be turned on, and you should walk around the pool while adding the chlorine or add the chlorine at a return jet slowly to allow the chlorine to mix with the water coming out. If you stand in one spot while you pour the chlorine, the sunlight can begin to destroy the chlorine before it has had a chance to mix with the cyanuric acid (conditioner) and be protected by it. You can lose 1 to 2 percent of the available chlorine if you don't "walk it around or mix it at a return jet." Chlorine is more effective if added late in the day. We realize pool service technicians are up early in the day, trying to service as many pools as possible before it gets too hot the daylight runs out, but it is true -- the later, the better. The pH of liquid chlorine is 13, so it causes a very alkaline condition to occur in the pool -- that is, it drastically raises the pH. It is therefore necessary to add about one quart of muriatic acid per 2 gallons of liquid chlorine. Because liquid chlorine does not have any cyanuric acid in it, you must use cyanuric acid separately to keep the chlorine in the pool from being degraded by sunlight. This saves you money, because in the summer, in direct sunlight, 95 percent of the chlorine in their pool could be destroyed in just two hours without it. Liquid chlorine will increase the total dissolved solids (TDS) of an average pool by roughly10 ppm for each gallon of liquid added due to the salts. This means the TDS will increase about 650 ppm annually, based on 65 gallons used over the year. This increase will make it necessary to drain the pool more often than gas chlorine, which means additional costs for chemicals to rebalance the water and additional cyanuric acid. . Return to Main Chemical Menu.
Calcium HypochloriteCal-hypo (calcium hypochlorite, chemical formula Ca(OCI)2) was patented in 1799 and was called "bleaching powder." It is produced by passing chlorine gas over slaked lime. The resulting powder or granules provide 65 to 70 percent available chlorine. Cal-hypo is stable and can be stored for long periods of time without significant loss in available chlorine level. It is granular form or as 1-inch or 3-inch tablets. It can be used for regular chlorination as well as superchlorination. It can be pre-dissolved in water and then added as a liquid to the pool if needed. It quickly forms hypochlorous acid (the killing form of chlorine). One pound of calcium hypochlorite provides about 2/3 or .65 pounds of available chlorine. Cal-hypo is classified as an extreme oxidizer. Except for gas chlorine, all the other types of chlorine are classified as oxidizers. Cal-hypo will support combustion. Avoid mixing cal-hypo with acids, ammonia, soda pop, oil, trichlor or just about anything but water. Mixing with organics will cause a fire. Be careful when sweeping around chemical-storage areas. Mixing the dust and spillage of various products together and then putting them into a trash can or dumpster may cause a fire. Clean up product spills separately. When adding cal-hypo to a concrete pool it must be broadcast or pre-dissolved. Avoid concentrating the product in any one area. Cal-hypo will temporarily cloud the water, because the calcium takes a long time to dissolve completely. Do not broadcast cal-hypo into a vinyl-liner pool. It will not dissolve before it hits the bottom. Once on the bottom, it will bleach the color out of the vinyl and will weaken the vinyl. You must use a feeder or pre-dissolve it in water and then add it to a vinyl-liner pool. Depending on local water conditions, using cal-hypo will increase the hardness level by an average of 3 to 10 ppm per month or about .5 to 2.5 ppm for each pound you add to an average 15 x 30 pool. This may make it necessary to test the hardness level in the pool more often. Because one pound of cal-hypo provides .65 pounds of available chlorine, you will need 100 pounds of cal-hypo to get the same as 65 gallons of liquid chlorine or 65 pounds of gas chlorine. The pH of cal-hypo is 11.8, so it causes an alkaline condition to occur,-- that is, it raises the pH. It is therefore necessary to add about 4 ounces of muriatic acid per pound of cal-hypo or about 3 gallons of muriatic acid per 100 pounds of cal-hypo. Because cal-hypo does not have any cyanuric acid in it, you must use cyanuric acid separately to keep the chlorine in the pool from being degraded by sunlight. This saves you money, because in the summer, in direct sunlight, 95 percent of the chlorine in the pool could be destroyed in just two hours without it.
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Lithium HypochloriteLithium hypochlorite (chemical formula LiOCl) is one of the most recently developed forms of chlorine. It is produced by bubbling chlorine gas through a solution of lithium, sodium and potassium sulfates. When dried, the result is a free-flowing powder that provides 35 percent available chlorine. Lithium hypochlorite is calcium free, dust free and non-flammable. It has a long shelf life (it will lose only .l percent of its available chlorine level per month), and because it contains no calcium, it dissolves rapidly without clouding. Because it is highly soluble, lithium hypochlorite can be used in vinyl liner pools. When broadcast over the surface of the pool the it will dissolve before it reaches the bottom. It can be used for regular and superchlorination, but because it dissolves so rapidly, it cannot be used in a dry-chlorine feeder. (you could, however, pre-dissolve it and dispense it in a liquid feeder.) One pound of lithium hypochlorite provides about 1/3 or .35 Pounds of available chlorine. Of the six most popular types of chlorine lithium-hypo is the most expensive to use You will need to get 186 pounds of lithium-hypo to get 65 pounds of available chlorine. The pH of lithium hypochlorite is 10.7, so it causes an alkaline condition to occur in the pool--that is, it raises the pH. You will need to add about 4 ounces of muriatic acid per pound of lithium hypochlorite or about 6 gallons to neutralize the effect of 186 pounds of lithium-hypo. Because lithium hypochlorite does not have any cyanuric acid in it, you must use cyanuric acid separately to keep the chlorine in the pool from being degraded by sunlight. This saves you money, because in the summer, in direct sunlight, 95 percent of the chlorine in the pool could be destroyed in just two hours without it. The same as cal-hypo, liquid, and gas chlorine.
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Sodium DichlorSodium Dichlor (sodium dichloro-s-triazinetrione, chemical formula NaCl2C3N3O3) is the only popular type of chlorine that does not require the addition of either a neutralizing chemical or cyanuric acid. Sodium Dichlor is produced by adding soda ash and cyanuric acid to a solution of trichlor. When dried the result is a granule that may provide 56 percent or 62 percent available chlorine, depending on the method of manufacture. The 56-percent formulation is by far the most readily available of the two. Sodium Dichlor is fast dissolving, will not cloud the water and has a long shelf life. It can be used for regular and superchlorination. Because it is fast dissolving, it cannot be used in a dry chemical feeder. Nor can you pre-dissolve it and dispense it in a liquid chlorinator. Because use of sodium dichlor can cause a buildup of cyanuric acid in the pool water as it is 57% stabilizer (cyanuric acid) by weight. It is necessary to check the cyanuric acid level more frequently and to partially drain and refill the pool if the cyanuric acid level exceeds 100 ppm. One pound of sodium dichlor contains slightly more than 1/2 (.56) pound of available chlorine and .57 pounds stabilizer. Of the six most popular types of chlorine, sodium dichlor is the second most expensive per pound of available chlorine. It does not however have any "hidden cost" associated with it. Sodium Dichlor has near-neutral pH and does not require any neutralizing chemical to be added to the water. And because it already contains cyanuric acid, it does not require addition of that chemical, either. One pound of sodium dichlor provides .56 pounds of available chlorine. You need to get 116 pounds to get that same 65 pounds or gallons of available gas or liquid chlorine.
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Trichlor (Tabs)Trichlor (trichloro-s-triazinetrione, chemical formula Cl3C3N3O3) contains the highest percentage of available chlorine of all the types of chlorine compounds. Trichlor is produced by drying and cooling the sodium salt of cyanuric acid in the presence of chlorine gas. The resulting compound Provides 90-percent available chlorine. Trichlor is mostly available as a l-inch tablet, 3-inch tablet, a stick or a cartridge. It has a long shelf life, and it is very slow dissolving, so it works extremely well in floaters and erosion-type feeders. It can be used for regular chlorination but not for superchlorination, because it dissolves too slowly. The granular form can be used as a "spot algaecide." Trichlor does not require the addition of cyanuric acid to the pool water. Because trichlor is highly acidic, it can harm equipment or pool plaster if improperly used. Placing a trichlor tablets in a skimmer can corrode metal pipes and fittings, and the corroded metal, usually copper, will deposit on the pool walls as a turquoise discoloration. Severe cases will result in blue fingernails and green hair for swimmers. Because use of trichlor can cause a buildup of cyanuric acid in the pool water, it is necessary to check the cyanuric acid level more frequently and to partially drain and refill the pool if the level exceeds 100 ppm. One pound of trichlor provides 9/10 (.9) pounds of available chlorine. Because it provides 90-percent available chlorine, 72 pounds of trichlor will supply the 65 pounds of available chlorine necessary to sanitize a "typical" pool of 15 x 30 for 1 year. The pH of trichlor is 2.8-3.0, so it causes an acidic condition to occur in the pool -- that is, it lowers the pH. It is therefore necessary to add about 4 1/2 ounces of soda ash for each pound of trichlor used. Because trichlor already contains cyanuric acid, it does not require addition of that chemical.
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Introduction to BromineEven though the vast majority of pools in the United States and Canada are sanitized with chlorine, more pools each year are starting to use bromine. A very large number of spas are already using bromine. Liquid, elemental bromine when added to water readily forms hypobromous acid (chemical formula HOBr) and hypobromite ions (chemical formula OBr-). Hypobromous acid is the killing form of bromine. Liquid, elemental bromine was used briefly in the 1930s and early 1940s to disinfect pools, but toxicity, high cost and extraordinary problems in handling, transportation and storage caused its use to be discontinued. Today, only compounds of bromine are available for water disinfection. Bromine is 2.25 times heavier than chlorine, and at a pH of 7.5 the killing form of bromine (hypobromous acid) is at 94%. You will need twice the amount of bromine as you would pound for pound of available chlorine. Therefore if you need 1 ounce of available chlorine to sanitize your hot tub then you will need 2 ounces of available bromine to do the same job. Bromine cannot be protected from ultra violet light like chlorine can, so it is not practical to use in an outdoor pool. In just 2 short hours of bright sunlight you can loose as much as 65% of your bromine from your pool. It should be noted that unprotected chlorine loses under the same conditions can exceed 90% without the use of stabilizer. Hypobromous acid is converted into back into sodium bromide by sunlight which can be reactivated back into hypobromous acid with the addition of an oxidizer like potassium monopersulfate or chlorine to the water. Chlorine does not have this ability, once chlorine is spent it cannot be reactivated like bromine. There are two basic bromine systems available in our industry -- a l-part and a 2-part system -- and each has its own characteristics.
1 Part BromineOne-part bromine or bromine tablets are actually a compound of bromine and chlorine (1-bromo-3-chloro-5,5-dimethylhydantoin also called BCDMH), (chemical formula BrClC5H6O2N2,). The chlorine in the tabs is used to oxidize the bromine to produce hypobromous acid and hypobromite ions. Bromine tabs provide an available bromine level of about 2/3 or 61-65 % and an available chlorine level of about 1/3 or 27-31%. One-part bromine (BCDMH) is mostly available as a 1-inch tablets, cartridges or packets. It has a long shelf life, and it is very slow dissolving, so it works extremely well in floaters and erosion-type feeders. Because bromine tablets are acidic (the pH of a 1-percent solution in distilled water is 3.6, and the pH of a l-percent solution in de-ionized water is 4.6) they can harm equipment or pool plaster if improperly used. Placing bromine tablets directly in a skimmer rather than in a feeder can corrode metal pipes and fittings, and the corroded metal, usually copper, will deposit on the pool walls as a turquoise discoloration. Severe cases will result in blue fingernails and Green hair for swimmers. Bromine's biggest enemy is sunlight. Bromine can be destroyed by the UV rays of the sun. The destruction can be a rapid as 65-percent bromine loss in just 2 hours of summer-time direct sunlight. Unfortunately, there is not yet a chemical that you can add to the water to stabilize the bromine. Cyanuric acid -- used to protect chlorine from the damaging rays -- does not work for bromine. (Incidentally, the chlorine loss in 2 hours of direct sunlight without cyanuric acid in the water is more than 90 percent) However after the hypobromous acid destroys bacteria, algae or other organisms, or is destroyed itself by sunlight it returns to being bromide ions, which can be reactivated by adding an oxidizer. The hypobromous acid can also combine with ammonia and nitrogen compounds in the water from swimmers to form bromamines. However, these bromamines are active sanitizers, and they do not smell like their foul-smelling counterparts - chloramines. Although bromine itself is an oxidizer, it is not strong enough by itself to oxidize or destroy ammonia and nitrogen compounds in the water. It is therefore necessary to oxidize these swimmers wastes and reactivate the bromide ions by adding a stronger oxidizer -- usually any form of chlorine or a nonchlorine shock (potassium peroxymonosulfate). We already know that we are going to need 130 pounds of bromine tablets to sanitize our "typical" pool of 15 x 32. The pH of bromine tabs is 3.6, so it causes an acidic condition to occur in the pool -- that is, it lowers the pH. It is therefore necessary to add about 3 1/2 ounces of soda ash for each pound of bromine tabs used. The bromine manufacturers also said that to oxidize away the bromamines formed and the swimmer waste, it would require about 35 pounds of potassium peroxymonosulfate or 35 pounds of calcium hypochlorite a year in addition to the bromine tablets for a "typical" 15 x30 pool. Oxidizer is added to activate the bromide into hypobromous acid. After the hypobromous acid destroys bacteria, algae or other organisms, it returns to being bromide ions (or bromide salts), which can be reactivated by adding an oxidizer. The hypobromous acid can also combine with ammonia and nitrogen in the water from swimmers to form bromamines. However, these bromamines are active sanitizers, and they do not smell like their foul-smelling counterparts - chloramines. Although bromine itself is an oxidizer, it is not strong enough by itself to oxidize or destroy ammonia and nitrogen compounds in the water. It is therefore necessary to oxidize these swimmers wastes and reactivate the bromide ions by adding a stronger oxidizer -- usually any form of chlorine or a nonchlorine shock (potassium peroxymonosulfate). 2 part bromine has a relatively neutral pH, but varies with different manufacturers from 6.5 to 8 and usually averages around 7. Bromine cannot be stabilized from the sunlight with the addition of cyanuric acid, as a mater of fact there is nothing at this time that will protect bromine from Uv light as mentioned in the previous " bromine tablet or 1 part bromine article". Return to Main Chemical Menu.
Shock Treating/ Super ChlorinatingAs we stated earlier in this article, shock treating or shocking refers to the addition of anything to the water that will remove or destroy ammonia and nitrogen compounds -- the process that we know as oxidation. Until about 15 years ago, chlorine was the only practical chemical to use for oxidizing organic contaminants, the term superchlorination really meant the same thing as shock treatment. But the introduction of non-chlorine shock products has changed that, and today, when we shock treat pool water, we do not necessarily superchlorinate it. To understand how non-chlorine shocks work, we should first understand how organic contaminants are formed, how chlorine destroys them and why we want to get rid of them in the first place. Organic matter and ammonia compounds enter a swimming pool or spa from many sources. Swimmers and bathers are major contributors -- their bodies give off saliva, sweat, urine and fecal matter -- but windblown dust, fertilizers, algae, leaves, twigs, certain water-treatment chemicals and even rain also introduce contaminants into the water. When chlorine is added to the water, it combined with these ammonia and nitrogen compounds to form chloramines. These chloramines (also known as combined chlorine) smell bad, and they are eye and body irritants. Not only that, they also disable the free chlorine. Chloramines are still disinfectants, but they are 40 to 60 times less effective than free chlorine. And in a swimming pool or spa, we want a fast, effective kill. Therefore, we want the presence of a lot of free available chlorine. So we need to get rid of the combined chlorine. In pools that are sanitized with bromine, the odor problem does not exist, and combined bromine (bromamines) are as effective as free bromine for disinfection. Nevertheless, it is still necessary to periodically oxidize the organic wastes to prevent them from building up and becoming sources of irritation. The first step in dealing with the problem of combined chlorine is to test the water to see how much of the chlorine in the water is free and how much is combined. The commonly used OTO test will not perform this task -- it can only tell you the total chlorine level and can't differentiate between free and combined chlorine. However, a DPD test kit or a syringaldazine test strip will do the job. Historically, chlorine has been used to destroy the organic waste in swimming pool water. The process that we commonly refer to as superchlorination is also known as breakpoint chlorination. Here's how it works:
"How Chlorine Reacts with Ammonia."When chlorine is introduced into swimming pool or spa water containing ammonia, the hypochlorous acid (free chlorine) quickly begins to oxidize the ammonia to form a combined chlorine compound known as monochloramine (only one chlorine molecule is attached to the nitrogen or ammonia). The reaction process does not stop here. More chlorine is required to continue the oxidation of the nitrogen or ammonia. If no more chlorine was in the pool or added, the pool or spa water would have a large amount of combined chlorine as monochloramine rather than the desired free chlorine. As more chlorine is added, the monochloramine is now oxidized by the additional chlorine to form dichloramine (two chlorine molecules attached to the nitrogen -- Reaction #2). Again, the reaction is still not yet complete. More chlorine is still required. As more free chlorine is added, it attacks or oxidizes the dichloramine to form trichloramine (Reaction #3). Finally, as even more free chlorine is added, the trichloramine is broken down or oxidized to simple nitrogen and chloride salt (Reaction #4), thus completing breakpoint chlorination. Theoretically, any chlorine added after this point can only exist as free chlorine, as long as no new contamination of the pool or spa occurs, such as bather waste. Of course, this is all but impossible. The pool or spa is subject to so many sources of contamination -- such as water passing through a dirty filter -- that it simply will not stay free of contaminants for very long. Keep in mind that the moment organic contaminants such as ammonia begin to re-enter the pool or spa, chloramines will begin to reform. Superchlorination to truly achieve breakpoint -- the destruction of all organic waste -- can be a very tricky thing to accomplish. If not enough chlorine is added, the combined chlorine problem is only made worse. When this happens, eye burn and skin irritation are not reduced, but rather raised to, very high and very irritating levels. If too much chlorine is added, it may take days to drop to safe levels (less than 5 ppm) before bathing can be resumed. How do we know how much chlorine to add to assure that breakpoint is achieved but without overdosing with the chlorine? By chemical calculation, chemists know that it takes 7.6 parts of chlorine to oxidize 1 part of ammonia. But a number of other factors will affect that ratio: Other organics or products in the water will consume some of the added chlorine so that 7.6 parts are not enough. To be practical, it's best to add 10 parts of chlorine for each part of ammonia. Of course, if the pool or spa is extremely dirty and contaminated, it could take 25 parts or more of chlorine. As a general rule of thumb, the addition of 10 times the combined chlorine level will achieve breakpoint. In other words, if the water has 0.5 ppm of combined chlorine by test, you will need to add 5ppm or more of chlorine. The next obstacle is to calculate the amount of a particular chlorine product to add. As discussed earlier on this page, each of the popular types of chlorine products provides a different amount of available chlorine when added to water. In our "typical" (18,000-gallon) pool, it will take about 1 1/2 pounds of available chlorine to achieve 10 parts per million. Using the chlorine conversion chart, you can find just how much of each type of chlorine will be required to provide this amount. One problem that has always existed with superchlorination is that if you do not add enough chlorine to the water to achieve breakpoint, you actually make the problem worse, because all you have done is increase the level of combined chlorine. And if you add too much chlorine, you will not only reach breakpoint, but you will also make so much excess free chlorine that swimming will need to be discontinued until the free chlorine residual drops to a safe level for swimmers (less than 5 ppm). In an indoor pool, this could take several days and could have a major financial impact on a commercial pool, where lost swimming time means lost revenue. Several of the disadvantages of using chlorine as a shock treatment are overcome by the use of non-chlorine shocks. Non-Chlorine ShockThe active ingredient in these non-chlorine shock products is potassium peroxymonosulfate, also known as permonosulfate. Like chlorine, permonosulfate is an oxidizer that will destroy organic contaminants such as ammonia in swimming pools and spas. However, permonosulfate compounds do not kill or disinfect they simply control organics and combined chlorine, helping assure that the chlorine can do its job as a sanitizer. Permonosulfates oxidize by using the element after which oxidation got its name -- oxygen. Oxygen is a pure form of oxidizer. Unlike superchlorination which is used to destroy problems such as odors, eye and skin irritation after they occur -- Permonosulfates are effective in preventing these problems. Because permonosulfates do not contain chlorine, but rather oxidize waste through the use of oxygen, they do not go through the various stages of chloramine formation to achieve breakpoint. Instead, they react directly with the ammonia to produce chloride and nitrogen. So no matter how little of the non-chlorine shock you add, at least some of the organic contaminants will be destroyed, and no additional chloramines will be formed. This overcomes one major drawback of superchlorination. And if you overdose with a non-chlorine shock by adding more than is required, no extended waiting period is needed before swimming can be resumed. Although bathers should not be present when any chemical is added to the water, swimming can be resumed after the permonosulfate has had a chance to dissipate, usually in just a few minutes. In fact, the excess chemical will remain in the water, ready to destroy any contaminants that may enter the pool from bather waste and other sources. Permonosulfates are 100-percent soluble and will not leave a residue or bleach vinyl liners or swimming suits. Because they are chlorine-based, it is not necessary to calculate how much to add to beat a given chloramine problem. Permonosulfates help prevent chloramines from forming, so whatever quantity is applied will have some positive result. Unlike superchlorination, which requires you to figure out how much chlorine to add and how often to correct problems, permonosulfates, are generally added at the rate of 1 pound per 10,000 gallons on a regular, weekly basis. Permonosulfates effectively control the formation of
chloramines, which cause odors, reduce disinfection and cause eye and skin
irritation. Permonosulfates cause an acidic condition to occur, that is they
have a low pH of about 2.3 to 3, so steps will need to be taken to counter act
the acidic condition that may be caused by using them. However permonosulfates
do not add to the calcium or other undesirable solids or cyanuric acid in the
water. Also, no special handling is required, and there is no reason to close
the pool or spa or to restrict swimming due to excessive chlorine residuals.
Finally. there is no need to calculate how much to add in order to be effective.
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Oxidizer and Chlorine Summary.
To find out your cost of available chlorine per pound or kilogram, divide cost by the % of chlorine available in that product. for example if Cal Hypo cost you $17.50/Pound then 17.5 divided by .65 = $26.92 per pound of available chlorine. If you do this with all the sanitizers you compare, you will then find the cost of each and be able to decide better which is for you. Also keep in mind when comparing products the additional costs of neutralizing there effects on pH. Also factor in the cost of stabilizing them from Ultra Violet light if that is applicable to you. Bromine is extremely difficult to calculate do to many factors such as the oxidizers (chlorine or non-chlorine shock) that are required to activate Sodium Bromide, and that it can't be stabilized from UV light. It should also be noted that you don't always need to add Bromine to the water to disinfect and oxidize because Bromide Salts can be re-activated time after time by oxidizing them providing of course that the are not destroyed by UV.
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Ozone GasOzone is a gas, a modified highly reactive form of oxygen (chemical formula O3) that is one of the strongest oxidizers and disinfectant available. It is stronger than chlorine, bromine, hydrogen peroxide and hypochlorous acid. In fact, against a bacterium called E.Coli (commonly used to measure the effectiveness of sanitizers), ozone kills 25 times more powerful than hypochlorous acid (chlorine) and about 500 times faster. There are two main methods of producing ozone. In a corona discharge method, air is passed through an electrically charged chamber, where a miniature “lightning storm” produces ozone from oxygen. In the UV method, air is passed close to one or more Ultraviolet lamps, which bombard the oxygen molecules with UV rays to produce ozone. Ozone is measured in parts per billion (units that are 1000 times smaller than parts per million) up to about 1 ppm or measured in milli grams. If you use an ozone generator in combination with chlorine or bromine , you merely need less chlorine or bromine. Test for the chlorine or bromine residual as you normally would. You will find that it takes a lot less chlorine or bromine to maintain that residual as much as 95% less, because much of the sanitizing chore is being carried out by the ozone. Also a pool or spa requires a lower residual of chlorine or bromine to maintain adequate sterilization. For a pool about .5 ppm is sufficient and a spa only requires 1ppm. Stand alone, ozone cannot oxidize such compounds as ammonia, urea or amino acids (all common bather wastes). However it can oxidize these simple compounds once chlorine or bromine has combined with them. Also ozone only stays in pool or spa water for about 18 minutes under ideal conditions of pH, temperature, contaminates etc.... however, it usually only lasts about 20 second to 6 minutes in most spas and pools. When ozone is first introduced into the water and during the first 72 hours or so, your water may get cloudy. Ozone will begin to oxidize all of those particles and metals that your present sanitizer would otherwise leave in the water. When these particles are oxidized, they form visible particles that are heavier than water and precipitate out. Also some of the dirt and debris in the water is to small to be trapped by the filter. These small-sized particles have a weak electrical charge or pole. The charge is a negative charge and they repel each other like two magnets. They are so small they are not affected by gravity and won't settle out. Ozone neutralizes these charges allowing the particles to combine into large enough particles to be trapped by the filter. Once the oxygen has do its job it reverts back to oxygen which will make the water look, feel and even taste better. Read more about ozone at Alternative Sanitizers Return to Main Chemical Menu.
StabilizerIn 1958, cyanuric acid (a weak acid) also known as CYA , conditioner or stabilizer, was found to protect chlorine in pool water from ultra violet light. Losses of chlorine from pool water due to ultra violet light are extremely high. UV light degrades chlorine by a chemical reaction in which two chlorine molecules combine with two molecules of water to form four molecules of hydrochloric acid also known as muriatic acid plus oxygen. As mentioned before a chlorinated pool without CYA will lose 90% of its chlorine in just 2 hours in the sun, because of this reaction. The mechanism by which CYA stabilizes chlorine is not known. However, the excepted theory is that hypochlorous acid (HOCl- the killing for of chlorine in water) and hypochlorite ions (OCl- -a relatively inactive form of chlorine in water) closely attach to one of the 3 free bonding sides of the CYA molecule. As long as they remain attached, they will not be degraded by sunlight. The chlorine is still readily available to work on bacteria and algae. However if there is an excess of CYA in the water (over 100 ppm) and chlorine begins to loss its ability to sanitize as it is being tied up so to speak, by the CYA. Also more importantly the health department doesn't like to see CYA go above 100 ppm as there is concern about the toxicity of cyanuric acid. While there are no known cases of cyanuric acid poisoning, health officials limit the CYA level to an upper limit of 100 ppm. When dissolved in water at 25 ppm the free chlorine residuals would last 3-5 time longer than pool water not containing CYA. At above 50 ppm, no marginal stabilization benefit is observed. It is generally recommended that you maintain a residual of 30-50 ppm of conditioner. To obtain 50 ppm of CYA requires you to add 4 pounds of conditioner for each 10,000 gallons of water to be protected, or 1 lb./5000 gallons yields 25 ppm. Remember to avoid CYA level over 100 ppm. This commonly happens from regular addition of stabilized chlorine like Dichlor or Trichlor. Cyanuric acid is removed from the pool water only by draining/dilution, splash out and backwashing, so it does need to be checked periodically. Usually spring and fall will do unless you use stabilized chlorine frequently then you may want to check the CYA more frequently. |
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