As described in our recently published article titled “Do-it-yourself guide to winterizing your above ground pool”, lowering the water level is an important step in the pool winterization process. Your swimming pool water necessarily contains chemicals at all times, of course, but chemical levels should be especially high if you have just balanced and treated the water to prep it for winter. Either scenario results in draining water that contains some chemicals. What’s an eco-friendly pool owner to do?
Drain the water into a secondary receptacle such as a large kiddie pool. If you haven’t recently added a superchlorinator and chlorine levels are low enough, you can let the water de-chlorinate naturally by waiting a day before disposing of it. Do not wait longer than that, however, because bacteria, algae, and other organic matter will form, causing you to introduce potentially harmful bacteria and protozoa into the water supply or environment. If you’ve recently utilized a winterizing chemical package or chlorine levels are otherwise still high, add a de-chlorinator such as sodium thiosulfate to the secondary tub. This works quickly and can be purchased in solid or powered forms.
If no such secondary receptacle is available, we recommend deferring balancing and treating the water until chlorine levels fall to an acceptable point (e.g. < 0.1 mg/L) and you are able to safely drain off enough water. If this is the case for you, verify whether your local municipality has a water treatment plant. If so, you may be able to drain your water near the sewer drain knowing the plant will handle any issues. Note that in many municipalities discharging pool water into a sewer system without sanitization can lead to hefty fines, so check with the proper local authorities to determine applicable rules and regulations. After de-chlorination, test the phosphate levels. This is an important step because introducing high levels of phosphates into streams, lakes and groundwater stimulates excessive plant growth and depletes water of oxygen. This creates issues such as algae blooms or fish kills. If phosphate levels are 200 ppb or above use a phosphate remover before disposing of the water. Phosphate ions do not break down naturally so adding a remover is a must.