Pool User Load - CPO® Math Tutorial

A Tropical Aquatics Educational Program

Things to know about User Load

LEARN HOW TO OPERATE YOUR PUBLIC POOL SPA FACILITY
Not all states or municipalities use the same method in determining maximum bather load (BL).

Some illustrations are:
  • Square foot of water surface area.
  • Flow Rate (usually Flow Rate divided by 5)
  • Gallons of water in the pool
  • Different factors for areas of shallow, deep and
    diving portions of the pool as well as the deck

    Always operate in compliance with your
    local or state code requirements.
The commonly accepted bather load calculation for spas is:
  • 10 sq.ft. for every user or BL = A divided by 10
Example:
  • You have a spa with a diameter of 11 feet.
    What is the bather load?

    The formula is BL = A divided by 10
    But what is A?
    Diameter = 11 feet
    Therefore r = ½ of 11, or 5.5 feet
    A = 3.14 x r x r
    A = 3.14 x 5.5 ft x 5.5 ft
    A = 3.14 x 30.25 ft2
    A = 95 sq.ft.
    BL = A divided by 10
    BL = 95 sq.ft. divided by 10 = 9 bathers
    (always round in the direction of safety, in this case, down)

Filter Area is very much related to the manufacturer's specification for the amount of water flow through the filter in question. These specifications are governed by standards as established by the National Sanitation Foundation International (NSFI). The CPO® student should review the next section covering Filter Media Rates before any further examples are offered regarding filter sizing.



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