The summer season is the time of year every pool owner and retailer most anticipate. After spending half of the year indoors working or with children in school, it is the perfect time to unwind. Families and friends gather for barbecues and parties to take advantage of a refreshing and relaxing dip in a sparkling blue pool. The past two years looked different from what many are used to, especially with lifestyle changes, hardships, and challenges caused by the pandemic. Most stayed at home for much of 2020 and 2021, but those with pools had unique backyard havens to escape some of the challenges.
Keeping the pool in near-perfect condition requires effort through the entire season, not just at openings and closings. Due to a variety of reasons, toward the latter half of the season, it is not uncommon to see water quality problems that have not presented themselves since the pool was opened. There are a few things retailers and service technicians should keep in mind to tailor recommendations to better prevent unsightly conditions before they become frustrating problems or hazardous to swimmer health. Helping clients remain on top of their pool maintenance routines can give owners a renewed sense of confidence their pool is as clean and safe as possible for everyone to enjoy.
Keeping the water clean and sanitized
Sanitizing the water of harmful organisms is one of the most important aspects of establishing an effective routine. Most pool owners choose chlorine because it is a powerful sanitizer that is compatible with most maintenance products available on the market. Chlorine will kill most biological organisms present in the water, but there are numerous contaminants that can be removed without relying solely on chlorine. With increased demand for pool chemicals, there are other ways to help maintain the water as desired.
Sanitizing
Since free chlorine has a short half-life under direct ultraviolet (UV) light and the chlorine residual depletes quickly, stabilizer in the form of cyanuric acid can be added for protection. Many trichlor-based tablets are formulated to further slow tablet dissolution. Some will have components with added benefits such as clarification or scale inhibition. A variable-speed pump (VSP) is worth considering, in which the pool owner can program a schedule of different speed settings and run times throughout the day. For tabs dissolving only when the pump is turned on, this not only can help slow dissolution, but can potentially reduce energy costs. Chlorinators can be fully loaded with tabs and adjusted to keep up with free chlorine residual changes due to weather changes or swimmer load. The best practice with pool owners with floating tablet dispensers is to begin the season with the floater fully open and reduce as necessary. Adjust until a significant free chlorine residual can be properly maintained for at least 24 hours. There are also supplemental chemicals to help remove unwanted contaminants while chlorine targets biological organisms.
Oxidation importance
Rain, source water, swimmers, thunderstorms, and nearby vegetation introduce waste products that need to be destroyed and removed. Some professionals and pool owners will only apply oxidizers to remediate major issues, such as an algae outbreak or enhance cloudy water. Shocking weekly to oxidize these contaminants introduced is typically a more economically sound way to help maintain a clean pool. During oxidation, electrons are transferred between hypochlorous acid and its target. Nitrogen and many nitrogenous compounds are a common target for chlorine because they react with chlorine readily. To prevent nitrogenous compounds from continuing to react with the free chlorine needed for proper sanitization, apply a maintenance shock weekly. It is also effective to shock after rainstorms or heavy pool use. Physically removing visible debris such as leaves, pine straw, or tree limbs as soon as they are apparent can help avoid major problems and chlorine depletion. Preventing contaminants from accumulating through use of a regular maintenance shock will help avoid fighting uphill and expensive battles with super-chlorination or water dilutions.
Water balance and impact on chlorine
Balanced water is not only important for protecting pool surfaces and equipment, but it also influences chlorine’s efficiency. When chlorine is administered to the water, it dissociates into hypochlorous acid (HOCl) and hypochlorite (OCl–). HOCl, the killing form needed to sanitize and oxidize, is most effective at sanitization when maintained in neutral environments with a pH in the range of 7.4 to 7.6.
HOCl ß à H+ + OCl–
Water with a lower pH shifts the equilibrium left to make more HOCl. If the pH exceeds 7.6, the equilibrium shifts to generate more OCl–, which is about 80 to 100 times less effective. Negatively charged micro-organisms are repelled by OCl-’s weaker negative charge and, therefore, are not as effectively killed. Keeping the pH in mind is needed when selecting a chlorine form, whether it be trichlor, calcium hypochlorite, liquid chlorine, or saline, as they all have differing impacts on the pH of the water.
Influence of total alkalinity and sanitizer type
Keeping total alkalinity in range is also critical for controlling pH balance. A total alkalinity below 40 parts per million (ppm) causes pH swings that are difficult to correct. Low total alkalinity can decrease the pH, which can impact swimmer comfort and be detrimental to pool surfaces and equipment. Effects to alkalinity are important when evaluating the options for a chlorine-based sanitization program. Sodium hydroxide, the byproduct introduced by both salt chlorinators and sodium and calcium hypochlorite, drives a more alkaline environment where cloudy water or detrimental scale-inducing conditions if not counterbalanced by the appropriate amount of acid. At the opposite end of the spectrum, trichlor’s acidity over time erodes total alkalinity depending on quantity applied, and pH balance of source and rainwater. Total alkalinity should be measured weekly and maintained at 80 to 150 ppm to best maintain pH between 7.2 and 7.6.
Using water temperature to sanitizer and balance
Water temperature is the single non-chemical balance factor to keep in mind, especially when extreme conditions occur. It is important in calculating the Langelier Saturation Index (LSI), and chlorine’s ability to control bacteria, algae, and other micro-organisms. Temperature, water hardness, total alkalinity, pH, and total dissolved solids (TDS) are all a part of the calculation required to evaluate the overall water balance. Higher temperatures tip the water toward more scaling conditions, whereas lower temperatures create corrosive conditions. The warmer temperature from the first half of the season combined with high total alkalinity and high calcium hardness, can force calcium out of solution and form scale deposits. Not only is scale unsightly and frustrating to remove, it can be problematic toward pool equipment. For a chlorine-generator, scale formation on the electrolytic cell can cause the generator to underperform and reduce its life expectancy. Cleaning the cell regularly with an acidic solution should be done to remove any hard deposits. A calcium sequestering agent should be added monthly to prevent this from happening, especially in pools with higher than average total alkalinities.
Warmer water has a great impact on chlorine as well. The demand on chlorine is greater in warmer conditions, especially if adequate stabilizer is not present to block out UV from sunlight. During June and July, the water temperature is at its warmest, often exceeding the normal 26 to 28 C (78 to 82 F) range in some places. The warmer water speeds up dissolution of slow-dissolving tablets, which may require more frequent replacements if the free chlorine residual is not being maintained. The warmer temperature and the wet environment make a comfortable place for organisms to thrive, which means free chlorine has more work to do. Testing measurable free chlorine regularly is imperative. Testing will reveal more chlorine is needed, especially as more swimmers take advantage of the warmer water. A booster shock may be needed to break up combined chlorine, or the output of a chlorinator may need an adjustment. Understanding the pool’s behaviour, events, and the surrounding environment as the summer moves along is important to making the appropriate changes to the routine.
The warm and wet environment is particularly appealing to algae. Being sure to brush areas of stagnant areas, at least weekly, will be necessary. Adding a maintenance algaecide weekly, as opposed to biweekly, should be explored. Quat-based algaecides will tackle most types, but if the pool is in an area where more resistant types are common, a polyquat or a chelated copper-based algaecide would be better choices. How much and how often free chlorine needs to be replenished varies depending on water circulation and filtration patterns, bather load, source water, and even the natural surrounding environment.
Colder water and LSI
Most residential pools operate between 26 to 28 C (78 and 82 F) during the pool season, but warmer water is not the only temperature extreme to keep in mind. Cooler temperatures make the water more corrosive to a pool’s equipment, especially the heater. Prolonged exposure to surfaces may cause etching. Metal staining may be more prominent as well. A metal chelating product or sequestrant should be included in the routine, especially when pool temperatures drop toward the end of the season or those with unheated pools. Filter aids, following the use of a chelating product, such as a charged cellulose can be used to help better guide problem-causing metals to the filter, where they can be eventually permanently removed. Temperature does vary, especially in more northern regions where water may not reach average temperatures without a heater. Remember, the water could be in range for pH and total alkalinity but still lean on the corrosive side with colder temperatures. This will also be important for best winterization practices at the end of the season.
Ancillary products—clarifiers and enzymes
Sanitization is highly important to keeping the pool clean, but it should not be the only component. Ancillary chemicals, such as clarifiers or enzymes, can help break down non-living contaminants so chlorine does not have to waste its energy in their removal. Clarifiers can help bind small particles together into bigger polymeric chains the filter will be able to hold onto. Chlorine and adequate filtration will remove visible contaminants from the water, but oils and dirt inevitably deposit along the waterline despite standard efforts. An enzyme is a naturally derived catalytic protein that can often be used to break down organic matter into more manageable forms. Specialized enzymes are often picked for removing nitrogenous amino acids, fats, or oils. Some products even pair different types of enzymes together to combat more than one type of contaminant. Many products will incorporate enzyme technology with a surfactant or phosphate remover. The synergistic relationship of enzyme and surfactants make dual-action ancillary maintenance product performance results more improved. With surfactants, a hydrophobic ‘tail’ attaches to oils at the surface, while a hydrophilic ‘head’ lifts oils from the surface where they enter the water to be broken down and removed by filtration. These also help prevent oily buildup in the filter. Phosphate removing products can help prevent calcium phosphate precipitation, and even have clarifying abilities of their own. The elimination of these oxidizable non-living wastes reduces the demand on chlorine and improves the overall water quality.
Conclusion
The last two years have been an uphill battle, but backyard investments do not have to be. Every pool has its own unique behaviours and nuances. Using a smart maintenance plan and being flexible to adjust as necessary will help overcome the late-season slumps pool owners often face. In addition to remaining on top of the free chlorine residual, using supplemental products will all work together to keep a pool a fun, clean, and relaxing place for the clients’ family members and guests. A clean pool can be a nice and rewarding escape from all the stresses of the last year and a half.
Emily Johnson, born and raised in South Carolina, graduated with a bachelor of science degree in biological sciences and chemistry minor from the University of South Carolina. She is a recreational water enthusiast living in Atlanta, Ga., with her two rescue dogs who love a good dip in a splasher pool. She has been working for research and development at BioLab Inc., a KIK Custom Products Company, since 2014. She can be reached via email at emily.johnson@biolabinc.com.
