Many homes' water tanks have the water temperature set higher than necessary. This Water Temperature Card will help you learn if your hot Water Temperature setting is appropriate. If it is higher than necessary then turning down the water tank temperature setting will reduce your energy costs. Run the hot water from a faucet for 3 to 5 minutes. Fill a cup with hot water and insert the card. If the number appearing along the black temperature strip is green then the number that appears is the temperature of your hot water. If the number is blue the temperature is higher than the number displayed. If it is tan then the temperature is less than the number displayed. When the number appearing is within the red square the water temperature is higher than 150 degrees Fahrenheit. The highest needed water tank temperature is usually 140 degrees Fahrenheit, and in some cases can be set at 120 degrees Fahrenheit.