You don’t have to leave pet water fountains running all of the time, but they are designed to do so. In some cases, you probably should, and there are a few reasons why you might want to. Electric and battery-powered pet water fountains use a pump to recycle water through a filter to keep it free of debris and bacteria. If you stop that pumping action, it takes extra effort on the pump's part to start that circulation process again. u003cbr/u003eu003cbr/u003eTurning the pump off also gives time for bacterial growth. The filter then has to play catch up. Second, an electric water fountain that’s constantly running often attracts pets. For animals that may not drink enough, the constant access to moving water can encourage them to drink more. However, if you let the water fountain run continuously, you must make sure it doesn’t run dry and burn out the pump.