Editor’s note: Due to the seasonality of the pool and spa industry and the transient nature of the business, the water treatment information provided in this article can be shared with service technicians who are new to the job.

Spring can be an exciting time for pool owners. Everyone looks forward to opening the pool and another season of making many family memories. However, pool opening is often quite stressful—especially for maintenance technicians new to the job—as problems may arise that were not anticipated and, in some cases, can be difficult and frustrating to handle. Many times, these issues can be avoided if dealt with appropriately during the off-season, and more so if the pool is closed properly. In the event there are water quality problems, they can be handled with the proper steps and a little patience.

When opening a pool, there are a few universal steps that should always be taken; however, before worrying about the water, it is important to handle all of the physical maintenance aspects first. This means making sure all of the equipment is working properly. If the pool was covered, every attempt should be made to remove it without allowing debris (on top of the cover) to enter the pool. Once the cover is removed, it should be cleaned and stored properly. If the pool was partially drained, it needs to be filled to the appropriate level before the equipment is started. All of the equipment should be inspected for leaks or damage and the manufacturer’s instructions for start-up procedures should be followed.

Once the equipment is operating properly, it is then time to deal with the water. However, before taking a water sample, the pool should be allowed to circulate for 24 hours as there are certain components of the water that will stratify or end up in layers.

For example, heavier components will end up at the bottom; therefore, taking a water sample prior to circulating the water will skew any test results and cause improper recommendations. Once the water has circulated and is tested properly, it can be balanced and then any problems can be handled appropriately.

It is recommended the total alkalinity is balanced first, and then the pH, followed by the calcium hardness. The stabilizer should also be tested and adjusted if needed; however, many pools are in a chlorine-demand state upon opening. Pools in this condition will often produce false-negative test results.

In other words, the stabilizer is present, but in some instances, it will not show up on tests when the pool is in a chlorine-demand state. This phenomenon is not completely understood; however, it does happen frequently. Once the chlorine demand has been treated, the stabilizer will show up on the test. For this reason, chlorine demand issues should be treated first, then the water should be re-tested so the stabilizer can be adjusted (if necessary).

The remainder of this article will focus on specific problems, solutions, and preventative measures for some of the more common issues often faced during pool openings.

Problem: Algae growth

Cause: Algae can begin to proliferate over the course of winter, especially in warmer climates or those regions with mild winters. Green algae are the most common type found in pools upon opening. In fact, more than 7000 different species exist. Approximately 10 percent of these are marine species (found in the ocean) with the remainder being found in lakes, rivers, ponds, and pools.

Green algae are named for the chlorophyll (the molecule that captures light energy to carry-out photosynthesis) in the cell which gives them their green color. Green algae can be free-floating or surface clinging and can be found in all pool types. They are typically the easiest to treat; however, some species may be more difficult to manage than others. Interestingly, although plants generally need light to proliferate, there are many species that will grow with little to no light available. They can proliferate in covered pools and on filter beds.

Treatment: If the pool is swampy, a floc should be added first as it will drop material to the bottom of the pool so it can be removed by vacuum. Once this has been completed, the water balance should be checked and adjusted (if needed). A chlorinating product should also be added to raise the chlorine levels above one part per million (ppm), then an algaecide should be applied. It is best to run the pump 24 hours per day while treating the pool for algae to help clear the water faster. Using a clarifier will also help to polish the water as the treatment
is being completed.

Prevention: The pool should be closed properly to ensure the water is balanced and has a chlorine residual—preferably on the high end (approximately 4 ppm). A winter algaecide should also be added. In milder climates, or those with warmer winters, a mid-season treatment will be necessary. In the spring, starting the pool on a program that includes the use of a maintenance algaecide will help to prevent algae throughout the season.

Problem: Chlorine demand

Cause: Chlorine demand is defined as the inability for pool water to maintain a chlorine residual—even after repeated application of a chlorinating product. There are an infinite number of substances that can contribute to chlorine demand. These include (but are not limited to) bacteria, algae, ammonia, urine, sweat, health and beauty products, and bather and animal waste.

These contaminants can enter the water in a number of different ways, including source water, rainwater, animals, fertilizers, plants/leaves, industrial pollution, and bathers (during the season). Any contaminant that can be oxidized will react with chlorine and deplete the level. During the off-season, run-off or rainwater can be a concern if it contaminated with materials such as ammonia, fertilizer, or industrial pollution.

Mesh covers, in particular, allow these contaminants to enter the pool water. In addition, source water is likely to contain ammonia, and this will be an issue when topping off the pool upon opening.

Chlorine demand is most likely caused by a combination of different types of contaminants, so the treatment time and difficulty could vary.

Treatment: As mentioned previously, if the water is swampy, a floc can be used to help drop material to the bottom of the pool, allowing some of the contaminants to be physically removed.

When starting treatment, the water should be balanced and the filtration system should be working properly. Chlorine should then be applied until a residual can be maintained. It is important to keep timing in mind when treating a chlorine demand issue. For instance, checking the chlorine residual a few hours after treatment may show the presence of free chlorine, and one might assume the demand is broken and no further product application is needed.

However, if slow-reacting contaminants are present in the water, the chlorine can be used up as they continue to react. As a result, the chlorine residual will end up at zero as more time passes, which means the demand is not truly broken.

This is why it is very important to add—as per the instructions—the entire amount of recommended product and continuing to test frequently to ensure the free chlorine residual holds between 1 and 4 ppm for 24 to 36 hours. If the chlorine demand includes algae growth, an algaecide should be applied.

Prevention: To prevent problems with chlorine demand it is important the pool is closed properly. The water must be balanced and have a chlorine residual, preferably on the high end (approximately 4 ppm). A winter algaecide should also be added. In milder climates or those with warmer winters, a mid-season treatment will also be necessary.

When the pool is opened, a treatment program that includes routine shocking/oxidation should be used to eliminate contaminants and keep the water clear. Typically, the shock/oxidizer products should be applied weekly. However, once the season is in full swing, more frequent application may be necessary based on weather or bather load.

Problem: Cloudy water

Cause: Cloudy water is one of the most predominant water quality issues in the pool industry. Pool owners respond more intently to cloudy water than any other water issue because of its effect on the pool’s esthetic appearance.

As it is identified through mere visual observation, any pool owner can recognize cloudy water and know it is an indication that something in the water requires attention. The difficulty, however, is diagnosing the specific problem and devising a solution that adequately clears the water.

The cloudiness or haziness of water is caused by the introduction of suspended particles that are invisible to the naked eye. A similar analogy would be the particles in air that cause smoke. These impurities are introduced to the water from a myriad of sources—essentially any particulate debris that comes from the surrounding environment, including air, dirt, clay, silt, pollen, inorganic/organic matter, and algae. Microbial organisms can contribute to water cloudiness, too.

Even bathers and source water contribute to the impurities that cause cloudy water. Consequently, pools are constantly exposed to such contaminants and require proper maintenance to ensure a clean and aesthetically pleasing swimming environment.

Treatment: To treat this problem, it generally involves narrowing down the cause of the cloudy water to either a chemical or physical property. High pH and calcium, chlorine demand, and algae growth are causes of cloudy water that need to be treated by adjusting the water balance. It can be frustrating, however, for the water to be in perfect balance, but still not look right.

Circulation and proper filtration are important to maintain clear water. The opening process offers a great opportunity to inspect the filtration system and evaluate the media. If the filter media was not cleaned upon closing, then it should be chemically cleaned during the pool opening. If the media is old and has not been replaced for several years, this is also a good time to install new filter media. Operating the pump 24 hours per day during treatment is a good practice.

Using a clarifier will also help to clear the water faster. Clarifiers generally consist of positively charged particles; contaminants in pool water carry a negative charge. These negatively charged contaminants are attracted to the positively charged clarifier and, as a result, this makes the particles bigger and easier to remove via filtration.

Prevention: To avoid cloudy water issues come spring, the pool should be closed properly by ensuring the water is balanced and has a chlorine residual preferably on the high end (approximately 4 ppm). A winter algaecide should also be added.

In milder climates or those with warmer winters, a mid-season treatment will be necessary. Once the pool is open and clear, always ensure the filtration system is working properly and run the pump at least 12 consecutive hours per day. It should not be broken into two or four-hour increments.

This best practice is explained by the Gage-Bidwell law of purification by consecutive dilution, which states the complete removal of dirt from a pool cannot be achieved over the course of one turnover. It requires a series of consecutive turnovers. The reason for this is pool systems operate by principles of continuous dilution. Purified water that enters the pool constantly mixes with the bulk reservoir, continually diluting the suspended particulates in the water. Therefore, a portion of the water at the circulation system intake (i.e. skimmers and drain) has already flowed through and been purified by the filtration system.

What Gage and Bidwell showed in their study was the amount of dirt removed from the system will only be approximately 63 percent at the end of the first turnover. As the average pool turnover rate is roughly six hours, running the pump for a lesser period will result in an even lower percentage of water that is cleaned by the filter.

As mentioned previously, a pool system that includes routine oxidation and a maintenance algaecide is best practice during the season. A maintenance clarifier can also be added to the system which will help the filtration system work more efficiently and help keep the water clear.

Problem: Scale

Cause: Calcium carbonate (scale) is not very soluble in water. As the calcium, pH, or carbonate level rises in the water, calcium carbonate will form and can precipitate. As this happens, it adheres to surfaces and equipment. Temperature also plays a role in this process, as calcium is more soluble in cold water, which also tends to be more corrosive.

For this reason, a little more calcium should be added to the water when closing the pool. This will adjust the saturation index slightly higher so, as the temperature drops, the water does not fall too far into the corrosive range. However, it is a delicate balancing act, as too much can cause scale to form as the water becomes warmer.

In areas where the source water already contains a high calcium level, this needs to be factored in each year during the pool opening process.

Treatment: If the pool was partially drained and the fill water is not high in calcium, the level will naturally dilute as the water is topped up before opening the pool. If the fill water is high in calcium, a scale inhibitor product should be added when the pool is being opened. It is important to ensure the product that is used is not only suitable for treating or inhibiting scale, but also is compatible with the sanitizer system being employed. For example, citric acid is not a scale inhibitor or preventer and is not compatible with a salt chlorinating sanitation system. The active ingredient can usually be found by looking at the safety data sheet (SDS).

Prevention: First and foremost, the pool water should be properly balanced upon closing the pool. A scale and corrosion preventer can also be added as part of the closing routine. In high calcium areas, a scale inhibitor product should be added on a monthly basis, again, ensuring the product is appropriate for the sanitizing system being used.

Special considerations for saltwater Swimming pools

Always follow the manufacturers’ instructions for the salt chlorine generator’s cell start-up process. If the cell was not cleaned when the pool was closed, then the opening process offers a great opportunity to clean it. The cell is prone to scale due to the high pH inside the unit. High pH is normal for this process and is a byproduct of chlorine generation. However, pool owners should be advised to do what they can to mitigate scale formation on the cell plates.

As scale builds on the cell plates, it reduces their ability to make adequate contact with the water, which impedes the production of chlorine. Cells must be cleaned periodically (on an annual basis) to ensure any scale is removed. When doing this, it is important that a scale inhibitor product appropriate for saltwater pools is used, even if the calcium in the water is not too high.

As saltwater pools are essentially chlorine-based sanitizers, all of the water quality problems discussed in this article could potentially be encountered. That said, the treatment process is the same—algaecide, shocking/oxidation, clarifiers, and pump run time. Saltwater pools may require some supplemental chlorine product upon opening until the generator is producing chlorine at the desired level. It is advisable to continue using an appropriate scale inhibitor product throughout the season regardless of the calcium level.

What is the takeaway? It is important to close the pool properly in the fall. Any problems that exist during this time will not go away over the course of the off-season. However, if these problems are encountered come spring, there are remedies to prevent them from happening again. With the proper treatment procedures and a little patience, pool downtime can be kept to a minimum.

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This article was written by Karen Rigsby and originally appeared on Pool & Spa Marketing [link].