How to Calculate Heat Loss in an Open Hot Water Tank With a Lid

The heat loss from an open hot water tank, such as a backyard swimming pool, can be substantial. It can also cost a considerable amount of money to continually replace the lost heat. Although less heat is lost when a cover is used, heat loss still occurs. For an uncovered tank, you must take into account the heat lost through water evaporation, heat radiation, and the heat lost through the walls of the tank. (Total heat lost = heat lost through evaporation + heat lost through radiation + heat lost through tank walls) For a covered tank, however, the lid acts as just another wall of the tank, so the measurements of evaporation and radiation are not necessary.

Things You'll Need

  • Measuring tape
  • Pencil
  • Paper
  • Calculator
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Instructions

  1. Calculate Surface Area of Tank

    • 1

      Measure the length and width of all tank surfaces (including bottom, walls, and lid or cover).

    • 2

      Multiply the length and width of each surface to find the surface area. (10 feet by 15 feet = 150 square feet).

    • 3

      Add the surface areas of the lid, bottom, and sides to get the total surface area of the tank.

    Calculate Heat Loss

    • 4

      Identify how thick the walls of your tank are, in inches.

    • 5

      Refer to this chart at the Engineeringtoolbox.com website, to determine you heat loss in BTUs per hour per square foot. A BTU, or British Thermal Unit, is the amount of heat energy needed to heat 1 pound of water 1 degree Fahrenheit.

    • 6

      Multiply the number of BTUs lost per hour per square foot by the total square footage of the surface area of your tank. This is the number of BTUs your tank loses per hour.