The piping with all valves and fittings which is used to connect the filter system together as a unit. This includes all valves and piping necessary for the filter plant to perform the functions of filtering or backwashing, either by the plant as a whole or any unit operating singly.
FACTOR OF SAFETY
The ultimate load divided by the safe load or the ultimate strength divided by the allowable stress.
FEED WATER
Water under pressure entering a purification system or an individual piece of purification equipment, such as an ultra filter, distiller or reverse osmosis system.
FEET OF HEAD
A basis for indicating the resistance in a hydraulic system, equivalent to the height of a column of water that would cause the same resistance (100 feet of head equals 43 pounds per square inch). The total head is the sum of all resistances in a complete operating system. The principal factors affecting a head are vertical distances and the resistance caused by friction between the fluid and pipe walls.
FERRIC IRON
Small solid iron particles containing trivalent iron, usually as gelatinous ferric hydroxide or ferric oxide, which are suspended in water and visible as "rusty water". Ferric iron can normally be removed by filtration. Also called "precipitated iron".
FERROUS IRON
A divalent iron ion, usually as ferrous bicarbonate which, when dissolved in water, produces a clear solution. It is usually removed by cation exchange water softening. Also called "clear water" iron.
FILTER
A device that separates solid particles from water by recirculating the water through a porous substance (a filter medium element). Permanent Medium Filter: A filter that utilizes a medium that under normal use will not have to be replaced. Diatomaceous Earth Filter: A filter that utilizes a thin layer of diatomaceous earth as its filter medium that periodically must be replaced. Cartridge Filter: A filter that utilizes a porous cartridge as its filter medium.
FILTER AGITATION
The mechanical or manual movement to dislodge the filter aid and dirt from the filter element.
FILTER AID
A type of finely divided media used to coat a septum type filter, usually diatomaceous earth or volcanic ash. (NOTE: Alum, as used on the bed of a sand filter, is also referred to as a filter aid).
FILTER CARTRIDGE
A filter which operates through a disposeable cartridge. These are of two general types: The surface or area type where the suspended matter is removed at the surface, and the depth type in which the interstices vary from large to small in depth.
FILTER CYCLE
The operating time between cleaning or bachwash cycles.
FILTER DIATOMITE
One designed to filter water through a thin layer of filter aid such as diatomaceous earth or volcanic ash. Diatomite filters may be of the Pressure, Gravity, Suction or Vacuum type.
FILTER ELEMENT
A device within a filter tank designed to entrap solids and conduct water to a manifold, collection header, pipe or similar conduit. A filter element usually consists of a septum and septum support.
FILTER MEDIA
The finely graded material which entraps suspended particles (sand, anthracite, diatomaceous earth, etc.).
FILTER ROCK
Graded, rounded rock and/or gravel used to support filter media.
FILTER SEPTUM
That part of the filter element consisting of cloth, wire screen or other porous material on which the filter cake is deposited.
FILTER, GRAVITY - SAND
A filter with a layer of filter media (usually silica sand) supported on graded gravel through which water flows by gravity.
FILTER, PRESSURE - SAND
A sand filter enclosed in a tank to operate under pressure.
FILTER, SAND
A type of filter media composed of hard sharp silica, quartz, or similar particles with proper grading for size and uniformity.
FILTER, VACUUM (SUCTION)
A filter which operates under a vacuum or from the suction side of a pump.
FILTRATE
The portion of the feed stream that has passed through the membrane or filtering media.
FILTRATION FLOW
The rate of flow in volume per time (gpm, gph), through the filter system installed per manufacturer’s instructions with a new, clean filter medium.
FILTRATION RATE
The rate of filtration of water through a filter during the filter cycle expressed in US gallons per minute per square foot of effective filter area.
FINA
The Federation Internationale de Natation Amateur – The governing body for intercollegiate competition including the Olympic games.
FLANGE
A device used to couple to a pipe on the suction or discharge of a pump.
FLOCCULATING AGENT
A compound, such as one of the alums, which forms minute flakes in water which attract or enmesh small suspended particles.
FLOCCULENT
Chemical which, when added to water, causes particles to coagulate into larger, settleable groupings. Aluminum compounds are common catalysts in this process.
FLOOR SLOPE
The slope in the pool floor, usually expressed in feet (or inches) of vertical rise in feet (or inches) of horizontal distance.
FLOW RATE OR CAPACITY
The volume of liquid that passes a given point in a specified unit of time.
FLOW VELOCITY
A quantitative expression of the rate of linear motion at which water passes through a pipe or conduit.
FLUIDIZATION
A process by which particles are suspended by an upward flow of liquid, such as may occur during back washing of ion exchange resin or carbon media.
FLUORIDE
A salt of hydrofluoric acid which may occur naturally in water supplies or be added by municipal processes for the prevention of dental caries. Fluoride is considered toxic in most medical settings and has been implicated with a wide range of physiological disorders including renal bone disease.
FLUX/FLUX RATE
The rate per unit of area at which water passes through a semi-permeable membrane, such as those used for ultrafiltration or reverse osmosis.
FOOT VALVE
A modified check valve that has a screen on the suction end to prevent debris from entering the pump or pipe.
FORCE
The applied effort used attempting to move something.
FOULING
The deposition of insoluble materials, such as bacteria, colloids, oxides and water-borne debris, onto the surface of a media such as water softening resins, reverse osmosis or ultrafiltration membrane. Fouling is associated with decreased flux rates and may also reduce the rejection rates of reverse osmosis membranes.
FREEBOARD
The clear vertical distance between the top of the filter medium and the lowest outlet of the upper distribution system in a permanent medium filter.
FRICTION
The resistance to motion by two objects or surfaces that touch.
FRICTION LOSS
The loss of pressure or head due to the resistance to flow in the pipe and fittings. Friction loss is influenced by pipe size and fluid velocity, and is usually expressed in feet of head.
FULVIC ACIDS
Acidic substances which are found in humic (organic) soils and which may become suspended in water. A component in the production of chloramines.
FUNGUS
A parasitic plant which produces no chlorophyll and is dependent on other life forms for its existence.