Glossary of Terms - F
A B C D E F G H I J K L M N O P Q R S T U V W Z
FAC - Free available (residual) chlorine.
fecal matter - Matter (feces) containing or derived from animal or human bodily wastes that are discharged through the anus.
ferric iron - Small solid iron particles which are suspended in water and visible as “rusty water”. Ferric iron can normally be removed by filtration.
ferrous iron - When dissolved in water, produces a clear solution. It is usually removed by a cation exchange water softener. Also called clear water iron.
filter - A device or system for the removal of taste, turbidity, color, iron, or odor.
Filter-Ag - The trade name for aluminum silicate (pumicite) granular product used as a general purpose filter medium.
filter area - The effective area through which water passes through filter media, often expressed in square feet. (See cross sectional area.)
filter media - A material used in a filter bed to form a barrier to the passage of certain suspended solids or dissolved molecules.
filtrate - The effluent liquid from a filter.
fines - Extremely small particles of filter media or ion exchange material which are smaller than the specified size for the medium, 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.
fixture unit - An arbitrary unit assigned to different types of plumbing fixtures, and used to estimate flow rate requirements and drain capacity requirements.
floc - A very fine, fluffy-type mass formed by the coming together of a number of fine suspended particles.
flocculation - The process of causing a "floc" to form after treatment with a coagulant by gentle stirring or mixing. (See coagulation.)
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 (tooth decay) in children.
flush tank - A tank or chamber in which water is stored for rapid release.
flush valve (flushometer) - A self-closing valve designed to release a large volume of water when tripped.
FMA - free mineral acidity (see mineral acidity).
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 (residual) chlorine (FAC) - That portion of the total available residual chlorine composed of dissolved chlorine gas (Cl2), hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-) remaining in the water after chlorination.
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 gas, or as carbonic acid, but not that combined in carbonates or bicarbonates.
free chlorine - See free available chlorine.
free mineral acidity (FMA)- See mineral acidity.