A wading pool is a great place for kids to stay cool and enjoy a splashing good time when the weather is warm. The one problem with these small pools is that they don't usually have a circulation or filtering system. Without chemical treatment, the water can quickly become murky and turgid, creating a perfect environment for bacteria and other organic compounds to grow. The simple solution is to add a small amount of chlorine to the water periodically to sanitize it and increase its effective life by balancing the water and buffering the chlorine.
Sanitizing a Wading Pool with Chlorine
Try to maintain a free chlorine level of 4.0 parts per million (ppm) in a wading pool. This is a higher level than you would maintain in a larger private pool, but with no filter to help remove debris, you need a higher sanitizer level to handle the bather load and organic material.
In a clean, freshly filled 500 gallon wading pool, add a quarter cup of unscented household liquid chlorine bleach to the water. Then, at the end of each day, test the water and add an additional 1/8 to 1/4 cup, depending on the reading. As it sits overnight, the chlorine will sanitize the water and breakdown organic compounds. Test the water the next morning before letting the kids use the pool to make sure it is in the safe range--at least 1.0 ppm, but not above 6.0 ppm. You can always lower a high chlorine level by adding more water.
The easiest way to test the sanitizer level is with DPD test strips, available at any pool supply store and many hardware and building supply stores. Dip a strip into the pool and compare the color on the strip to the color chart provided with the strips.
Stabilizing and Buffering the Water
After filling the pool and adding the initial dose of bleach, add a cup of baking soda. Stir the pool to dissolve it. This raises the alkalinity of the water, helping hold or stabilize the chlorine so it lasts longer and sanitizes more effectively. Add a half cup of 20 Mule Team Borax, available at any grocery store in the laundry detergent aisle. Borax buffers the pH level of the water, helps keep it clear and sparkling, and also acts as an algaecide.
You only need to add more baking soda and borax when the kids' mini-cannon balls and water play splash out more than a third of the pool's volume. Unlike chlorine, these two chemicals don't break down in the water. Replenish the water and add a proportionate amount of them as necessary at the end of the day along with the bleach.
Removing Dirt and Debris to Help Chlorine Do Its Job
Keep a small skimmer net on hand to remove grass, leaves and debris tracked in as the kids use the pool. These nets are available almost anywhere pool chemicals are sold. The less additional debris the chlorine has to "attack and destroy" in the water, the more effective small amounts will be in keeping the pool sanitary.