Water meters, or measurers (apparatus for the measurement of water),
are constructed upon two general principles: 1, an arrangement called
an “_inferential meter_” made to divert a certain proportion of the
water passing in the main pipe and by measuring accurately the small
stream diverted, _to infer_, or estimate the larger quantity; 2,
_the positive meter_; rotary piston meters are of the latter class
and the form usually found in connection with steam plants. They are
constructed on the positive displacement principle, and have only one
working part—a hard rubber rolling piston—rendering it almost, if not
entirely, exempt from liability to derangement. It measures equally
well on all sized openings, whether the pressure be small or great; and
its piston, being perfectly balanced, is almost frictionless in its
operation.
Constructed of composition (gun-metal) and hard rubber, it is not
liable to corrosion. An ingenious stuffing-box insures at all times a
perfectly dry and legible dial, or the registering mechanism which is
made of a combination of metals especially chosen for durability and
wear, and inclosed in a case of gun-metal.
[Illustration: Fig. 99.]
Fig. 99 is a perspective view of the meter, showing the index on the
top. It is shown here as when placed in position. The proper threads
at the inlet and outlet make it easy of attachment to the supply and
discharge pipes.
The hard rubber piston (the only working part of the Meter) is made
with spindle for moving the lever communicating with the intermediate
gear by which the dial is moved.
The water, through the continuous movement of the piston, passes
through the meter in an unbroken stream, in the same quantity as with
the pipe to which it is attached when the opening in the meter equals
that of the service pipe; the apparatus is noiseless and practically
without essential wear.
“POINTS” RELATING TO WATER METERS.
In setting a meter in position let it be plumb, and properly secured to
remain so. It should be well protected from frost.
If used in connection with a steam boiler, or under any other
conditions where it is exposed to a back pressure of steam or hot
water, it must be protected by a check valve, placed between the outlet
of the meter and the vessel it supplies.
It is absolutely necessary to blow out the supply pipe before setting a
new meter, so that if there be any accumulation of sand, gravel, etc.,
in it, the same may be expelled, and thus prevented from entering the
meter. Avoid using red lead in making joints. It is liable to work into
the meter and cause much annoyance by clogging the piston.
This engraving, Fig. 100, shows the counter of the Meter. It registers
cubic feet—one cubic foot being 7-48/100 U. S. gallons and is read in
the same way as the counters of gas meters.
[Illustration: Fig. 100.]
The following example and directions may be of service to those
unacquainted with the method:
If a pointer be between two figures, the smallest one must always be
taken. When the pointer is so near a figure that it seems to indicate
that figure exactly, look at the dial next below it in number, and if
the pointer there has passed 0, then the count should be read for that
figure. Let it be supposed that the pointers stand as in the above
engraving, they then read 28,187 cubic feet. The figures are omitted
from the dial marked “ONE,” because they represent but tenths of one
cubic foot, and hence are unimportant. From dial marked “10,” we get 7;
from the next marked “100,” we get 8; from the next marked “1,000,” we
get the figure 1; from the next marked “10,000,” the figure 8; from the
next marked “100,000,” the figure 2.
THE FISH TRAP used in connection with water meters is an apparatus (as
its name denotes) for holding back fishes, etc.