Algae
The other element of seasonal pool water care has to do with what grows in the water. Mould, algae, bacteria, viruses, and other micro-organisms all linger in the water regardless of the season. However, as the water temperature gets lower the activity of these micro-organisms also decrease, sometimes exponentially. So, similar to when the pool is open, there is as equal importance in eliminating them or at least keeping them under control, when it is closed for the season.
Universal in the approach to off-season water care is the use of a product that keeps algae growth under control—regardless if the pool is covered or left exposed to the elements. That said, there are essentially three types of algaecides to consider.
Algaecide can use quaternary ammonium compounds, or often referred to as a quat algaecides. These are inexpensive and have the potential of ridding the water of any existing algae. It is important to note, however, these algaecides—especially at higher concentrations—may cause foaming. Additionally, when administering high levels of chlorine to the water, the effectiveness of the quat-based algaecide is diminished.
Other algaecides commonly used contain poly dimethyliminio ethanediyl dichloride. These algaecides are usually referred to as poly algaecides. They are non-foaming and keep a greater residual in the water in the presence of chlorine.
Lastly, algaecides with the presence of copper are effective chemistries to combat algae in the long-term. These algae inhibitors are similar to poly algaecides as they are typically non-foaming and hold well in the water, even in the presence of chlorine.
Although these are the three basic types of algaecides used in pool winterization, there are other hybrid options available. Poly and copper hybrid algaecides is a growing market segment because they provide all the advantages of two separate algaecides in a single container.
The shocking truth
When closing the pool, shocking the water is a must to reduce the amount of contaminants. After the water is shocked, contaminant loads are reduced, which allows the disinfectant (sanitizer) to help control the other materials lingering in the water, either currently or later during the off-season. There are two different camps with respect to what works best. Some like to use chlorinated products, while others prefer to use non-chlorine oxidizing shocks.
Using chlorinating products to close a pool has its advantages. For instance, if chlorine levels are non-existent in the water then applying a chlorinating shock will simultaneously scourer the pool of algae, bacteria, and other contaminants, while leaving a residual in the water during the off-season. When unstabilized chlorines are used, the impact on the water’s pH is minimized.
Non-chlorine oxidizing shocks, relative to chlorine, are still new in the recreational water maintenance industry. Since most are comfortable with the ability of chlorine, most do not look at non-chlorine as an effective tool—especially when it comes to closing a pool. However, just because the product does not have chlorine present, it does not make it any less of an oxidizer. Non-chlorine oxidizers have the ability to scour more contaminants in the water than its chlorine counterpart. Further, these products will not combine with chlorine and possibly form any disinfection byproducts. Most importantly, its lack of chlorine is better for the long-term appearance of the pool’s surface. Regardless of its effectiveness as an oxidizer, a chlorine presence during the off-season is still a must.
Additional treatments
Depending where the pool is located (climate region), the amount of products used to close and/or maintain a pool over the winter, as well as the frequency of application, may vary. In Canada and the northern U.S., pools are typically treated only once as the cover prevents outside debris and waste materials from entering the water. In areas where pools are covered (or use mesh covers) that experience mid-winter thaws, additional algaecide treatments are important to keep the growth of micro-organisms under control.
In southern and southern-coastal communities, a pool cover is not generally used. The lack of a cover means the pool water can be exposed to outside debris and, of course, the sun, even though the temperature is cold. Due to the pool’s exposure, the water will need to be treated more often than a pool located in the north, but certainly less than when the pool is open for the season.
