fecal - Matter containing or derived from animal or human wastes or feces.
filter - A device or system for the removal of solid particles (suspended solids).
filter area - The effective area through which water passes through filter media, often expressed in square feet. (See cross sectional
area.)
filter medium - (See medium.)
filtrate - The effluent liquid from a filter.
fines - Extremely small particles of filter media or ion exchange material, often the result of breakage or chemical or physical deterioration.
fixture - In plumbing, a permanently installed device in which water is used, such as a faucet or toilet.
flow control - A device designed to limit or restrict the flow of water or regenerant; may include a throttling valve, an orifice of fixed
diameter, or a pressure compensating orifice.
flow rate - The quantity of water or regenerant which passes a given point in a specified unit of time, often expressed in gallons per minute.
fluoridation - The addition of a fluoride compound
to a water supply for the reduction in incidence of dental caries.
flush tank - A tank or chamber in which water is
stored for rapid release.
flush valve - A self-closing valve designed to
release a large volume of water when tripped.
fouling - The process in which undesirable foreign matter accumulates in a bed of water conditioning media, clogging pores and coating
surfaces and thus inhibiting or retarding the proper operation of the bed.
free available chlorine - The concentration of residual chlorine present as dissolved gas, hypochlorous acid or hypochlorite, not combined with ammonia or in other less readily available form.
freeboard - The vertical distance between a bed of filter media or ion exchange material and the overflow or collector for backwash water; the height above the bed of granular media available for bed expansion during
backwashing; may be expressed either as a linear distance or a percentage of bed
depth.
free carbon dioxide - Carbon dioxide present in water as the gas, or as carbonic acid, but not that combined in carbonates or bicarbonates.
free chlorine - See free available chlorine.
