Pool Area: Knowing how to calculate area is important for determining heat loss, sizing pool covers,
bather loads in spas, and in some states, bather loads in pools.
Pool Depth: Depths are never even throughout a pool or spa. They may be sloped or if the depth is
"constant", there is usually a coved or radius at the wall junctions.
Volume: Volume is the space inside of an object. When talking about the volume of a pool,
we express it in cubic feet. In metric terms, volume would be cubic meters.
Gallons: Cubic feet or cubic meters are not useful in everyday discussions. So we take it one
step further and convert to gallons or liters, things we know.
User Load: Usually user load is defined by local codes. Commonly, it is the number of bathers
(or users) in the body at any specific time.
Heater Sizing: A British Thermal Unit (BTU) is the amount of heat that will raise the temperature
of one pound of water, one degree Fahrenheit.
Turnover Rate: When the number of gallons in a pool goes through a filter, in 24 hours, that is
one turnover a day. Most states require 3, 4 or even more turnovers a day.
Flow Rate: The way to achieve turnover rate is with Flow Rate (FR). The minimum Flow Rate is that
which will realize the turnover rate (TR) requirements.
Filter Area: There are three basic filter types: sand; cartridge; and diatomaceous earth.
For the same Flow Rate, each type of filter has a different filter area requirement.
Filter Media Rate: Filter Media Rate (FMR) is a NSFI standard that determines how fast water can flow
through a given filter type.