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Off-season water care: Managing pool water balance and controlling organics

By Kevin Vlietstra

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 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.

Whether one calls it winterizing, closing, off-season, or end-of-season pool care—how pool professionals handle water care 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 those that can be used to control organics during the winter months. When both are tended to, the likelihood of a successful start-up next season will improve greatly.

Water balance

Mould, algae, bacteria, viruses, and other micro-organisms all linger in the water regardless of the season; therefore, 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.
Mould, algae, bacteria, viruses, and other micro-organisms all linger in the water regardless of the season; therefore, 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.

Water balance factors include pH, total alkalinity (TA), calcium hardness (CH), water temperature, and total dissolved solids (TDS). During the season, the goal is to maintain these water balance parameters to ‘ideal’ levels suggested by organizations such as the National Swimming Pool Foundation (NSPF). In these ideal conditions, whether at the lower or upper end of the scale, the water is close to being ‘balanced’ according to an equation that helps determine the potential for scaling. This equation is known typically as the Langlier Index or Saturation Index (LSI).

For example, the average water temperature for most pools during the season is approximately 27 C (82 F). As the peak of the season winds down, so do water temperatures and, as temperatures decrease, so does the indicating number in the LSI. This value describes the water’s potential to be more corrosive or aggressive. The chart (on the right) shows how the LSI number decreases as the water temperature decreases, no matter if the minimum or maximum ideal water care parameters are maintained. Certainly, the majority of pools are not maintained on these minimum and maximum levels, but the purpose is to demonstrate how important it is to make adjustments as the pool season winds down. By not responding appropriately, the risks of having a problem the following season become higher.

Regardless of geography, one of the ways to move the needle on LSI is adding an all-purpose sequestering treatment product prior to closing (or continuously) during the off-season. Sequestering products bond with soluble metals (such as calcium) to prevent the formation of scale. Essentially, this water treatment regimen moves the total LSI level to a higher, positive number. When traceable heavier metals are present, such as iron and copper, the use of all-purpose treatments helps to prevent those metals from creating stains and discolouring the water while the pool is not in use.

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