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Specialty Chemicals for Special Times

By Alicia Stephens & Brian Trenck


Proper pool care is based on three very important Ps: prevent disease, protect equipment, and provide the expected swimming experience. Maintaining adequate sanitation is a key element to proper pool and spa maintenance as it keeps bathers safe from disease and allows for clean, clear water. Using an oxidizer on a weekly basis, adding a preventative algaecide, good physical maintenance and select ancillary products round out the key components of a program that maximizes the impact of the sanitizer and helps provide the expected environment for swimmers.

There are many different sanitizer options for pools that include chlorine, bromine, salt chlorination and biguanide. While each of these sanitizers offers a different range of features and benefits, chlorine sanitization is the most common choice for pools and spas due to its ease of use and impact on water balance. Chlorine can be introduced to the water in many ways, including sticks, tablets, granules, liquid and chlorine generator systems. Regardless of which version is being used, each form leads to the formation of hypochlorous acid. Hypochlorous acid is the killing form of chlorine that does the work of preventing disease and maintaining the expected safe and clear environment in the pool or spa water.

Since all forms of chlorine lead to the same sanitizing compound, the features and benefits among different chlorine options are focused on the secondary impact of the chlorine type on overall water chemistry. Service professionals and homeowners make sanitizer choices based on many different factors. For example, trichlor comes in slow-dissolving sticks or tablets, making it the perfect choice for feeding through a chlorinator and allowing for fewer trips poolside for application. It's important to understand that trichlor also has a low pH and can affect total alkalinity as well as pH readings. Dichlor, on the other hand, is a quick-dissolving granule product that can be broadcast directly to the pool. Dichlor does not impact water balance, but it must be applied several times a week if it is being used as the primary sanitizer.

Trichlor and dichlor are both stabilized chlorine products. The primary difference between a stabilized and unstabilized chlorine product is the presence of cyanuric acid. Chlorine is not UV stable. This means that on its own, chlorine will degrade in the presence of sunlight rather quickly. Stabilizer protects chlorine from UV rays, and stabilized chlorine will last five to six times longer than unstabilized chlorine. Thus, bathers will be protected longer when stabilizer is present, or when stabilized chlorine products are used consistently to sanitize recreational water.

Sodium hypochlorite, or liquid chlorine, is inexpensive and easy to apply to the pool, but it has a very high pH that results in the need for routine application of a pH decreaser to maintain a balanced pH. Calcium hypochlorite comes in both tablet and granule form, giving a wide variety of application options. It's important to know that the pH of calcium hypochlorite is high, and the granules often require pre-dissolving before product addition. Hypochlorite products do not contain stabilizer, so stabilizer must be added directly to the pool in order to provide protection from UV degradation when using these products.

Due to current industry conditions, the use of liquid chlorine will become more prevalent for the upcoming pool season. This may be a new approach to sanitizing for many pool care professionals, so it's a good idea to review the features of liquid chlorine and how to maximize it as a sanitizer in a pool. Liquid chlorine, also known as sodium hypochlorite, is an unstabilized sanitizer with a pH of around 13. The benefits of liquid chlorine include its cost-effectiveness, as well as the ease of application. You can simply pour it in the pool without concern that it will bleach the surface. Remember that liquid chlorine is unstabilized, so when using it as the primary sanitizer, check and balance cyanuric acid independently of your sanitizer addition. A residual of 30-50 ppm of stabilizer is ideal to maximize the life of liquid chlorine and to protect it from UV degradation once it is added to the pool. Even with adequate stabilizer levels, liquid chlorine must be added frequently to maintain the EPA-required 1-4 ppm sanitizer residual needed to provide adequate sanitization for the pool.

In addition to stabilizer, there are other components and ancillary products to consider for maximizing the effectiveness of liquid chlorine. Water balance can play a big part. Remember, the pH of liquid chlorine is around 13. This will drive the pH of the pool water upward with each addition. At a high pH, chlorine is not as active as it should be, making it less effective at sanitizing the pool water. The industry recognized correction factor is 10-16 fluid ounces of muriatic acid for every gallon of liquid chlorine added to maintain a pH in the range of 7.2-7.6 are necessary to ensure chlorine is active and effective in the pool.

In addition to balancing the water, there are other products that can be added to a routine pool care program in order to maximize the impact of liquid chlorine. A preventive algaecide, which should be a part of any pool care maintenance program, is an important addition to the pool when trying to maintain an adequate chlorine residual with liquid chlorine. Adding an algaecide weekly allows chlorine to be used for killing bacteria, and not get used up killing algae. The less work chlorine needs to do in the pool, the longer it will last. For service professionals, choosing the right preventive algaecide is important. Certain algaecides could cause excessive foaming when water features or attached spas are present. Refer to label instructions for guidance.

The addition of an enzyme product on a weekly basis will also enhance the efficiency of any chlorine-based pool maintenance program. Enzymes break down non-living waste that is typically oxidized by higher levels of chlorine or a non-chlorine oxidizer. By using enzymes to break down the non-living waste (things like sunscreens, hair products, body oils, pollen and more) that are present in pool or spa water, the demand on chlorine is reduced. Less chlorine needed to maintain a residual is often evident in a maintenance program that uses enzymes consistently to break down non-living waste.

Another option for service professionals to improve water quality and ensure success with liquid chlorine is orthophosphate removal. When the phosphate level gets too high (roughly over 125ppb), it can create dull, cloudy or hazy water conditions and, in combination with high pH and calcium hardness, contribute to the formation of calcium phosphate scale on surfaces and equipment. This is especially problematic for saltwater pools. Since phosphate is the last step in the oxidation process of phosphorous, chlorine and shocks don't have an effect upon it, however, phosphate does contribute to the conditions that make it harder for chlorine and algaecide to do their jobs. Therefore, keeping a pool at a near-zero phosphate residual is the ideal goal. Testing for and removing phosphate proactively helps reduce reoccurring pool problems, simplifies pool maintenance needs, and improves both the look and feel of the water. Look for multifunctional weekly maintenance products that will add both enzymes and phosphate removers at the same time, maximizing the potential of liquid chlorine while minimizing the time poolside and the number of product additions needed.

Often the first tool a service professional reaches for poolside is a chemical. However, the value of improving or expanding routine physical maintenance is one of the most overlooked solutions by both service professionals and pool owners to maximize a pool care program. The benefits of properly circulating pool water, providing good filtration and even getting in a light personal workout by brushing and vacuuming is often understated.

If the sanitizer, or any other ancillary chemicals applied to the pool, can't reach problematic areas then the opportunity for problems to arise increases and the value of those additions is reduced. Specifically, for a sanitizer, if the sanitizer can't reach it, it can't kill it. Traditionally, pool water needed to be circulated 10 to 12 hours a day and turn over the volume of the water at least twice in a 24-hour period. However, with variable speed pumps allowing consumers to run their pumps for longer periods of time without breaking the bank, the standard 10 to 12 hours is more complex and flow patterns become more important.

Most consider the positioning of returns as an afterthought and think the more churn and surface disruption the better. In many cases this is not true. For instance, larger above-ground pools can struggle to maintain good circulation since the lack of a main drain and limited amount of surface skimmers makes it more difficult. Many also have returns improperly positioned to point up toward the surface of the pool to make water appear to be circulating vigorously. Despite looking great, the circulation is inadequate and leads to problems occurring faster at the bottom and center of the pool. These areas of reduced circulation become the landing spot for large amounts of debris, while the areas and seams where the pool floor meets the walls become a haven for the start of biofilm and algae growth. What collects in these dead spots consumes chlorine-based sanitizers that blindly attempt to react and breakdown nitrogen-rich pool contaminants.