Fine spun filaments of glass which are available in a rope or mat form. When
used in a process with polyester resins, catalysts and hardeners, can be formed
or molded into pools, spas and related shapes.
FILTER A device that
removes non-dissolved or suspended particles from water by re-circulating the
water through a porous substance (a filter medium or element). The three types
of filters used in pools and spas are sand, cartridge and D.E. (diatomaceous
A chemical compound added to the water or to the filter that allows the existing
filter to become more efficient. Examples are alum, water clarifiers and D.E.
FILTER AREA The total
surface area of the filter medium that is exposed to the flow of water from the
pump, expressed in square feet. Examples are: a 36 sq.ft. (also 36 ft2) D.E.
filter and a 100 sq.ft. (also 100 ft2) cartridge filter.
FILTER CARTRIDGE A
replaceable porous element made of paper or polyester used as the filter medium
in cartridge filters.
FILTER CYCLE The operating
time between cleaning or backwashing cycles of a filter. Also the amount of time
the filter has water flowing through it each day expressed in hours.
FILTER ELEMENT A device
within a filter tank designed to trap suspended solids as water flows through it
from the pool or spa.
FILTER MEDIUM The material
used in the filter to trap suspended dirt particles as the water is flowing
through it. The polyester or paper used in making a cartridge filter element.
The sand used in a sand filter. The D.E. (diatomaceous earth) used in a D.E.
FILTER POWDER A common
name for diatomaceous earth (D.E.), used as the filter medium in a diatomaceous
FILTER ROCK Graded,
rounded rock and/or gravel used to support the filter medium. Usually used with
rapid-rate sand filters.
FILTER SEPTUM That portion
of the filter element consisting of cloth, wire screen or other porous material
on which the filter medium or filter aid is deposited. The nylon grid on a D.E.
filter is the septum.
FILTER, SAND A type of
filter media composed of hard, sharp silica, quartz or similar particles with
proper grading for size and uniformity. The most common grade used is No. 20 in
FILTRATION FLOW The
design rate of flow, expressed in U.S. gallons per minute (gpm) or gallons per
hour (gph), through the filter system installed per manufacturer's instructions
with a new, clean filter medium.
FILTRATION RATE The rate
at which the water is traveling through the filter, expressed in U.S. gallons
per minute (gpm) per square foot of effective filter area.
FIREMAN'S SWITCH A
mechanical switch located inside the time clock, which opens a circuit and shuts
off the heater 10 or 15 minutes prior to shutting off the water circulation
pump, allowing the heater to cool down. This helps reduce lime buildup in the
(also see flocculation) - The clump
or tuft formed when suspended particles combine with a flocculating agent.
Also flocculant - A chemical substance or compound that promotes the
combination, agglomeration, aggregation or coagulation of suspended particles in
The combination, agglomeration, aggregation or coagulation of suspended
particles in such a way that they form small clumps or tufts (called floc).
FLOW RATE The quantity of
water flowing past a designated point within a specified time, such as the
number of gallons flowing past a point in 1 minute - abbreviated as gpm.
A froth of bubbles on the surface of the water. Usually comes from soap, oil,
deodorant, hair spray, suntan oil, etc., that is shed into the water as swimmers
FREE AVAILABLE CHLORINE
The amount of free chlorine in the pool or spa water that is available to
sanitize or disinfect the water. Sometimes called residual or available