Whether one calls it winterizing, closing, off-season, or end-of-season pool care—how service professionals deal with pool water once there is not much pool activity all boils down to what part of the country the pool is located. In all cases, the two variables that need to be addressed are: a) managing water balance and, b) controlling organics.
This article will focus on the various products that can be used to balance pool water as well as the products that can be used to control organics during the winter months. The likelihood of a successful spring start-up will improve greatly when both are taken into consideration.
Water balance factors include pH, total alkalinity (TA), calcium hardness (CH), water temperature, and total dissolved solids (TDS). During the season service professionals look to maintain these water balance levels to ‘ideal’ levels. In these ideal conditions, whether they are at the lower or upper end of the scale, the water is close to ‘balanced’ according to an equation that helps determine the potential for scaling. This equation is known as the Langelier Saturation Index (LSI) or saturation index.
For example, in terms of in-season water temperature, most pools are kept around 27.7 C (82 F). As the peak pool season winds down, so do water temperatures. As the temperatures decrease so does the indicating number in the LSI. This value describes the water’s potential to be more corrosive or aggressive. The LSI chart on the opposite page (see Figure 1) shows how the number decreases as the water temperature declines whether the minimum or maximum ideal water care parameters are being used. Of course, many pools will not register right on the minimum and maximum of the index; the purpose is to demonstrate how important it is to adjust during the pool’s last days that it remains open. Inaction may cause one to have to react to a problem next season.
Regardless of geography, one of the ways service techs can move the needle on the LSI scale is by adding an all-purpose sequestering treatment product prior to closing the homeowner’s pool or by adding it continuously throughout the off-season. These treatments bond with soluble metals (such as calcium) to prevent the formation of scale.
Essentially, this maintenance routine moves the total LSI reading to a higher positive number. When traceable heavier metals are present, such as iron and copper, the use of all-purpose treatments will prevent these metals from creating stains and discolouring the water when the pool is not being used.