By Terry Arko
Before draining a pool for closing, cleaning, or renovation, consider the effect the water will have on the environment. Unfortunately, swimming pools can contribute to the pollution and degradation of our waterways and oceans. As responsible owners, it’s important to realize how pools affect the environment and make every effort possible to minimize their environmental impact. More than 1000 fish died last October when water from a heavily chlorinated swimming pool in Vancouver was drained directly into the Musqueam Creek.
Another contamination problem arising from pool water can be excessive levels of nutrients, such as phosphates and nitrates. When lakes, rivers, and streams become overwhelmed with the by-products of increased agriculture and industry, the result is an influx of algae-enriching nutrients that decrease dissolved oxygen levels and kill fish. Nutrient-rich water in streams and rivers that flow to oceans cause persistent red tides comprising toxic algae that kill marine mammals and fish. Additionally, people who come in contact with algae may also develop respiratory illnesses. Environmental experts agree the only way to solve increasing algae problems is to limit the amount of nutrient pollutants entering our lakes, rivers, and streams.
Eco-Friendly Recommendations for Draining a Pool
When preparing to drain a pool, the first step is to evaluate the water’s condition. Has the pool been properly sanitized throughout the season or is it a swamp? Is the chlorine level high? Does the water contain high levels of metals or salts? Is it properly balanced? Has it been tested and treated for phosphates?
If the water hasn’t been sanitized recently or is in a swamp condition, super chlorinate it to kill bacteria, algae, and organic matter. If draining to the sewer is permitted, you may not need to super chlorinate the water, as it will be treated at the municipal plant. If you do super chlorinate before draining, decrease the chlorine to 30 ppm and hold it for 12 hours. This will inactivate most bacteria and protozoa that can be present.
Before draining your pool, ensure the water is dechlorinated. The best way to achieve this is to stop chlorinating the water so levels decrease naturally. Be sure to allow several days before draining. If it is not possible to allow the chlorine level to come down naturally, the pool can be quickly dechlorinated using sodium thiosulfate. It takes about 25 g (0.9 oz.) of sodium thiosulfate to remove 1 ppm of chlorine in 10,000 l (2642 gal) of pool water.