Proper pool care is based on three 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 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 method 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.
The secondary impact based on chlorine type
Since all forms of chlorine lead to the same sanitizing compound, the features and benefits among the different 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, while also reducing the number of trips one must go poolside for application. It is important to understand trichlor also has a low pH and can impact total alkalinity and 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 ultraviolet (UV) stable. This means 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. As a result, 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 an extremely high pH that results in the need for routine application of a pH decreaser to maintain proper water balance. Calcium hypochlorite is available in tablet and granule form, giving a wide variety of application options. It is important to know the pH of calcium hypochlorite is high, and the granules often require pre-dissolving before adding the product to the water.
Hypochlorite products do not contain stabilizer, so stabilizer must be added directly to the pool to provide protection from UV degradation when using these products.
The use of liquid chlorine on the rise
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 is 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 as it can be simply poured into the pool without concern that it will bleach the surface.
As it is unstabilized, when using liquid chlorine as the primary sanitizer it is important for service technicians to check and balance the cyanuric acid independently of the sanitizer application. A residual of 30 to 50 parts per million (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 required 1 to 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. For instance, water balance can play a big part. As the pH of liquid chlorine is around 13, this will drive the water’s pH upward with each application. When the pH of the water is high, chlorine is not as active as it should be, which makes it less effective. The industry recognized correction factor is 295.7 to 473 mL (10 to 16 fl oz) of muriatic acid for every 3.78 L (1 gal) of liquid chlorine added to maintain the water’s pH in the range of 7.2 to 7.6, which is necessary to ensure chlorine is active and effective in the pool.
