have some type of sensing device. More complex systems will include one or more of
the following elements: transmitter, indicator, and recorder. Modern I&C equipment
allows an operator to monitor and control equipment, flow rates, pressures, levels, and
processes not only at the water treatment plant, but for all parts of the distribution
network as well.
Water Meters. The primary function of water meters is to measure and
record the volume of water flowing in a line. Flow is the most important measurement
made at water supply facilities. Flow data is used to account for the water treated and
pumped to distribution, chemical flow pacing, long-range planning, etc. Various types
of meters and flow measuring devices, including flumes and weirs, are described in the
references cited in par. 9.2 above. Additional topics such as installation, testing
procedures and test equipment, recordkeeping, general maintenance, and repair of
meters may also be found in these references. Help calculating flow rates is provided in
Meter Reading. Meters are generally furnished with registers that
measure water flow in terms of flow rate or total volume. Water meter registers are
typically of two general types: the straight-reading type and the circular-reading type.
The straight-reading type is read like the odometer on a car. The meter register reports
the number indicated by the counting wheels. Fixed zeroes to the right of the counting
wheel window should be included in the meter reading. The circular reading dial is
somewhat difficult to read and has been gradually replaced by straight registers on new
meters. When a hand on any scale is between two numbers of a circular reading dial,
the lower number is read. If the hand seems exactly on any figure, check the hand on
the next lower scale. If that hand is on the left side of zero, read the figure on which the
hand lies. Otherwise, read the next lower figure.
Because the registers are never reset while the meters are in service, the
amounts recorded for any given period are determined by subtraction. To obtain the
volume of water that passed through the meter since the previous reading, subtract the
previously recorded reading from the present reading. The maximum amount that can
be indicated on the usual line meter before it turns to all zeros and starts over again is
99,999 cubic feet, or 999,999 gallons. Thus, to get a current measurement when the
reading is lower than the last previous one, add 100,000 to the present reading on a
cubic feet meter, or 1,000,000 to the present reading on a gallon meter. The small
denomination scale giving fractions of 1 cubic foot or 10 gallons is used for testing
purposes only and is disregarded in the regular reading.
Additional information regarding direct meter readout and remote reading
may be found in pars. 2.1.4 and 2.2.5.