3 August 1998
(16) Rated capacity. The rated capacity of a supply line, intake structure, treatment
plant or pumping unit is the amount of water which can be passed through the unit when it is
operating under design conditions.
(17) Cross connection. Two types recognized are:
(a) A direct cross connection is a physical connection between a supervised,
potable water supply and an unsupervised supply of unknown quality. An example of a direct
cross connection is a piping system connecting a raw water supply, used for industrial fire
fighting, to a municipal water system.
(b) An indirect cross connection is an arrangement whereby unsafe water, or
other liquid, may be blown, siphoned or otherwise diverted into a safe water system. Such
arrangements include unprotected potable water inlets in tanks, toilets, and lavatories that can
be submerged in unsafe water or other liquid. Under conditions of peak usage of potable
water or potable water shutoff for repairs, unsafe water or other liquid may backflow directly or
be back-siphoned through the inlet into the potable system. Indirect cross connections are
often termed "backflow connections" or "back-siphonage connections." An example is a direct
potable water connection to a sewage pump for intermittent use for flushing or priming. Cross
connections for Air Force facilities are defined in AFM 85-21.
b. Ground water supply definitions. The meanings of several terms used in relation to
wells and ground waters are as follows:
(1) Specific capacity. The specific capacity of a well is its yield per foot of drawdown
and is commonly expressed as liters per minute per meter (Lpm/m) of drawdown (gpm/ft).
(2) Vertical line shaft turbine pump. A vertical line shaft turbine pump is a centrifugal
pump, usually having from 1 to 20 stages, used in wells. The pump is located at or near the
pumping level of water in the well, but is driven by an electric motor or internal combustion
engine on the ground surface. Power is transmitted from the motor to the pump by a vertical
(3) Submersible turbine pump. A submersible turbine pump is a centrifugal turbine
pump driven by an electric motor which can operate when submerged in water. The motor is
usually located directly below the pump intake in the same housing as the pump. Electric
cables run from the ground surface down to the electric motor.