Oklahoma City, Oklahoma
Your Pool and Spa Service Company
Just like the first time driving a car -
especially if it was a stick shift, swimming pool care and water chemistry can
seem a bit confusing, at first, but with a little practice, and a firm grip of
the concept, pretty soon, it just becomes second nature.
There are 4 major components to Swimming pool water care: Sanitation, Corrosiveness, Cleanliness, and Clarity. Only if the pool water is in proper chemical balance, can the the filtration system effectively take care of the other two. While there a lot of possible complications to swimming pool chemistry, the average homeowner just needs to know the basics - the rest can be learned on a "need to know" basis. We'll cover those basics of pool chemistry here, and A-Pro Services will be happy to help with all the rest.
Chlorine and other Halogens - Still the most widely used, and, when used properly, the most over all cost efficient, chlorine has been used as an effective swimming pool water sanitizer since the dawn of swimming pools. A properly chlorinated pool should not have a strong chlorine odor, nor should it burn the eyes. Having too much chlorine in the water is just as bad as not enough. What usually causes chlorinated pools to be harsh is that there is not enough of the right kind of chlorine. Free chlorine is chlorine in the water that available to kill contaminates. Combined chlorine is chlorine which has already been used, but remains in the water. It is usually the combined chlorine that causes the strong chlorine smell often found at public facilities in the middle of the afternoon. What is the solution? Believe it or not, more chlorine!
Total chlorine - the sum of all the chlorine in the water, is measured in ppm, or parts per million. From that, if you subtract the amount of free chlorine and this tells you the level of combined chlorine in the water. When the combined chlorine level gets too high, they must be oxidized, that is, burnt of by super chlorination. That's right, more chlorine, not less.
The type of chlorine used to super chlorinate the pool is called shock. The least expensive type of shock, and most commonly used, is calcium hypochlorite. This type of chlorine is less stable, so it boosts the chlorine level very high for a short time, then goes away rather quickly, taking with it the "dead" chlorine and it's odor. There are also non chlorine shocks, like monopersulfates, which serve the same purpose: oxidation. They are more expensive, but many people use them because there is no wait time for the chlorine in the pool to return to a safe level. It is a good practice to shock the pool weekly, as well as after a storm, after heavy usage, or at the very slightest hint of algae in the pool. Shock, alone, is not the right chemical to use to clear up a green pool, but that's some of that "need to know" stuff.
Corrosion or scaling conditions in the water are determined by considering several factors. Total Alkalinity is, to put it simply, a measure of the water's ability to neutralize acid. Potential Hydrogen, or pH, is a measurement of the relative acidity of the pool at a given time. If the total alkalinity is low, the water is less able to neutralize acid, and therefore, the pH tends to drop. Likewise, if the total alkalinity is high, the pH tends to rise. Total Alkalinity is also known as Base. The base demand is a calculation of the total alkalinity needed to keep the pH pf the water stable. The Langlier Index, or water gram, takes into account the total alkalinity, calcium hardness (or Total Hardness) level, and water temperature to determine the pH of saturation. This is compared to the observed pH, to determine whether the water is corrosive, or scaling. Water that is within three points on the Langlier Index is considered to be in balance - meaning neither corrosive nor scaling.
Normally, the Ideal ranges are: pH: 7.2 - 7.8, with 7.4 being ideal. Total Alkalinity: 80-120. Total Hardness: 150-250. The exact ideal levels vary, but should fall within these ranges. note that it is high calcium levels in the pool water which tend to cause scale buildup on surfaces, in equipment, and plumbing
When making adjustments, since the pH is stabilized by the Total Alkalinity, you should always adjust the total alkalinity before attempting to adjust the pH. Total Alkalinity and pH are lowered by using muratic acid, or a dry acid like sodium bisulfate, which is often sold as "pH lower" or a similar name. To raise the pH, sodium carbonate, or Soda Ash is used. To raise the Total Alkalinity, sodium bicarbonate, or sodium hydrogen carbonate is used. As you may have noticed, sodium bicarbonate, often sold as Alkalinity Increaser, is simply baking soda. Soda ash is less stable, and effects pH more quickly and dramatically than bicarbonates.
Salt systems have become popular, largely because the proponents have done a good job of marketing the technology, and many people believe the water feels better and is easier to maintain. Service companies like to sell salt systems because the sale and installation are profitable, and because there is little to do when performing weekly maintenance. Retail stores who sell chlorine or other alternatives, and who do not have service departments, are not so big on salt systems.
Salt, chemically, is sodium chloride. Salt is added directly to the pool, until the proper level is reached, around 3000 parts per million. Salt systems use an electronic device to separate the chlorine from from the sodium, and use that chlorine as a sanitizer. The sodium then becomes sodium hydroxide which later recombines with the chlorine to reform salt. This is a continuous process, and, as long as the filtration system is on and the unit is in working order, the pool remains treated. Salt systems do not work when there is no circulation, so adjustments must be made if the pool pump is on a timer. The better salt systems have either manual or automatic methods for super chlorination, or "shocking" the pool. Once adjustments are made, salt systems are usually trouble free for several years with only minor maintenance. as with other sanitation methods, the pH, Total Alkalinity, and other corrosion factors must still be maintained independently from the sanitizer.
Copper has been used for many years in swimming pools as an effective algaecide, and as of late, is sold as the primary chemical in such products as Pristine Blue and KleenPool. Because copper is such an effective algaecide, it prevents the growth of many organics. Periodically, a halogen, like chlorine, or, more specifically, Sodium Dichloro-s-triazinetrione Dihydrate (dichlor) is used to oxidize the free copper, and establish a low level of free chlorine.
Silver is used in such products as Once-a-Week and Sildate. Silver oxidation systems are similar to copper systems, and often use non chlorine shock, or monopersulfates to oxidize the silver. Overusage of both copper and silver can lead to staining, so you should never use more than the manufacturer recommended amounts of these chemicals.
Biguanide is used in products such as SoftSwim and Baquacil and is only an effective sanitizer against bacteria. You must also apply weekly algaecide and shock treatments. Recommended range of 30 to 50 ppm. Biguanide systems use hydrogen peroxide as a shock chemical; follow the directions of your dealer or manufacturer. Be sure to make the shock and algaecide treatments on a routine basis.
Ozone is an effective sanitizer for quick kills, but has no residual killing power. Ozone generators are very effective in closed systems and is almost a standard feature in modern spas, They are also used in many public water supplies. Because of the short lifespan of ozone before it reverts back to oxygen, it is recommended that other, more stable sanitizers must be used along with ozone.
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There are many other aspects to swimming pool water chemistry, like chlorine stabilizers, algaecides, etc., but let's put them under the "Need to Know" category.
Using the basic knowledge provided here, you have the tools to understand basics of swimming pool water chemistry. If you do need to learn more about a particular swimming pool water chemistry issue, A-Pro Services is happy to help!
For information about other topics related to swimming pool care, service, repairs, and maintenance, pool please visit our other pages, liked above, or the links to our other sites.
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