I started worrying if we had a leak too because it seemed like the level is down every few days by about an inch. My wife assures me it's simply evaporating because it's been 100 degrees almost every day, it's only rained-rained once (and for only 10 minutes) in about 3 months and our backyard is always windy. As hot and dry as it's been I guess it is just normal evaporation.