How can you cool down swimming pool water during the dog days of summer?  Water Features. The easiest and cheapest way to cool your pool is to add a swimming pool water feature. There are many types available which can connect to your pool’s return line.  By spraying the water into the air some of it will evaporate, drawing heat out of the rest of the water and thereby cooling it down.You will get the best effect if you run the fountain at night, taking advantage of the cooler temperatures. Keep in mind, by running the fountains you will lose more water to evaporation than normal. This might not be the best option to consider if you are like many of us in Central Indiana on water restrictions due to drought conditions.