As owner and operator of a retail site selling pools and everything to do with pools and spas I am constantly amazed by the need for information on many of the basic products used by pool owners. Since chemicals are a universal, this and subsequent articles will hopefully give pool owners a better idea of what they're putting in their pools and how it will perform.



Chlorine is still King of Sanitizers for swimming pools. Chlorine and its relative Bromine are members of the halogen family of chemical elements. Halogens share the characteristic of being powerful oxidizers, which makes them ideal for swimming pools and spas. The oxidizing property breaks apart chemical contaminants from swimmers and the environment making the pool unattractive for infestation by algae and bacteria. Having said this swimming pool chlorine is available in a number of different forms each possessing unique properties. This article will discuss each popular type.

Bleach (sodium hypochlorite) is a liquid form of chlorine identical to the bleach used for laundry but in a more concentrated form. Laundry bleach usually provides 4-5 percent available chlorine while pool bleach is 10 percent or a little more. Bleach isn't a very good pool product compared to other types of chlorine available today. It's expensive; chorine in other forms delivers 56 to 90 percent available chlorine compared to 10 percent for bleach. Bleach also has a pH of over 13. This will tend to raise the pool pH unless pH reducer is added regularly. Bleach is unstabilized and easily broken down by the UV rays in sunlight. Once added to the pool it will be gone in about 2 hours. Bleach may also add dissolved solids that can make pool water cloudy and unattractive. Given the drawbacks and availability of better sources of chlorine bleach shouldn't be an option for use in a swimming pool.

Calcium Hypochlorite (Cal Hypo) is usually sold in granular form although tablets are available, typically for use in septic systems. Cal Hypo is most commonly found in 1 lb. bags sold as pool shock. Cal Hypo provides a healthy 65 percent available chlorine but as it is unstabilized sunlight quickly burns it out. If used as a regular source of chlorine, stabilizer (cyanuric acid) is usually added to the pool to keep the Cal Hypo from disappearing so quickly. Cal Hypo makes an effective shocking agent because it does its job and quickly disappears. There are several drawbacks to Calcium Hypochlorite. It is the most powerful oxidizer (Class II) available for pool owners and the most dangerous to store and handle. It can react explosively when mistakenly mixed with other chlorine products. It must also be pre-dissolved before use to avoid bleaching out vinyl liners.

Sodium Dichlor (Dichlor) is always sold as a granular product and provides 56 percent available chlorine. Typically more expensive than other forms it doesn't lend itself well to automatic feeders and provides a little less bang for the buck in available chlorine. On the plus side it is a Class 1 oxidizer and somewhat less dangerous to handle than other forms of chlorine especially bleach and Cal Hypo. It also makes an excellent shocking agent as it dissolves in water quite well. Dichlor has cyanuric acid added during production to stabilize the material so it stays around up to 6 hours in direct sunlight.

Sodium Trichlor (Trichlor) is the most widely used form of chlorine for swimming pools. Almost always sold in the form of tablets or sticks Trichlor provides 90 percent available chlorine. This is the highest percentage available which makes this type of chlorine the most cost effective. One 3 inch Trichlor tablet provides nearly seven times as much chlorine as a 4 gallon case of bleach. The formed product is ideal for automatic feeders and because it is also stabilized Trichlor will stay around for a while. Like its cousin Dichlor, Trichlor will not affect pH nearly as much as other products. Trichlor is also ideal for feeders because it requires flowing water to dissolve.

Each of these types of chlorine, except bleach, has its place in keeping pools clean and sanitary. Knowing the characteristics of each will help save money, time and effort caring for a swimming pool.