MIL-HDBK-1164
Aquiclude. A geologic formation which, although porous and capable of absorbing
water slowly, will not transmit it rapidly enough to furnish an appreciable supply for a
well or spring. The permeability is so low that, for all practical purposes, water
movement is precluded or severely restricted.
Aquifer. A water-bearing formation or stratum beneath the earth's surface which
transmits water from one point to another.
Artesian. An adjective applied to groundwater, or items connected with groundwater,
for example, a well, under ground basin, etc., where water is under pressure and will
rise to a higher elevation if afforded an opportunity to do so.
Backblowing. Reversal of the flow of water under pressure in a well to free the screen
or strainer and the aquifer of clogging material.
Backflow. The backing-up of water through a conduit or channel in the direction
opposite to normal flow.
Backflow Preventer. A device for a water supply pipe to prevent the backflow of water
into the water supply system from the connections on its outlet end.
Backsiphonage. The flowing back of contaminated or polluted water from plumbing
fixture or cross-connection, into a water supply line, because of a lowering of the
pressure in the line. Also termed "backflow."
Backwash. The reversal of flow through a filter to wash clogging material out of the
filtering medium and reduce conditions causing loss of head. Also called filter wash.
Bacteria. Primitive microscopic plants, generally free of pigment, which reproduce by
dividing in one, two, three plants. Do not require light for their life processes.
Bacteria Count. An estimate of the total number of bacteria of all kinds in 1-ml sample
which will grow at the stated temperature, usually 37C. Also standard plate count.
Base. An alkali or hydroxide of the alkali metals, and of ammonia, which neutralizes
acids to form salts and water. Ionizes to form (OH-) ions. A hydroxide. An alkali.
Basin. A natural or artificially created space or structure, surface or underground,
which by reason of its shape and the character of its confining material, is capable of
holding water. The term is sometimes used for a receptacle midway in size between a
reservoir and a tank.
Blowoff. A controlled outlet on a pipeline, tank, or conduit used to discharge water or
accumulations of material carried by the water.
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