_The Pipe Line_

The principal items of cost in installing an impulse wheel are in
connection with the pipe line, and the governor. In small heads, that
is, under 100 feet, the expense of pipe line is low. Frequently,
however, the governor will cost more than the water motor itself,
although cheaper, yet efficient, makes are now being put on the market
to meet this objection. In a later chapter, we will take up in detail
the question of governing the water wheel, and voltage regulation, and
will attempt to show how this expense may be practically eliminated by
the farmer.

To secure large heads, it is usually necessary to run a pipe line many
hundreds (and in many cases, many thousands) of feet from the flume to
the water wheel. Water flowing through pipes is subject to loss of
head, by friction, and for this reason the larger the pipe the less
the friction loss. Under no circumstances is it recommended to use a
pipe of less than two inches in diameter, even for the smallest water
motors; and with a two-inch pipe, the run should not exceed 200 feet.
Where heavy-pressure mains, such as those of municipal or commercial
water systems, are available, the problem of both water supply and
head becomes very simple. Merely ascertain the pressure of the water
in the mains _when flowing_, determine the amount of power required
(as illustrated in a succeeding chapter of this book), and install the
proper water motor with a suitably sized pipe.

Where one has his own water supply, however, and it is necessary to
lay pipe to secure the requisite fall, the problem is more difficult.
Friction in pipes acts in the same way as cutting down the head a
proportional amount; and by cutting down the head, your water motor
loses power in direct proportion to the number of feet head lost. This
head, obtained by subtracting friction and other losses from the
surveyed head, is called the _effective head_, and determines the
amount of power delivered at the nozzle.

The tables on pages 66-67 show the friction loss in pipes up to 12
inches in diameter, according to the amount of water, and the length
of pipe.

In this example it is seen that a 240-foot static head is reduced by
friction to 230.1 feet effective head. By referring to the table we
find the wheel fitting these conditions has a nozzle so small that it
cuts down the rate of flow of water in the big pipe to 4.4 feet a
second, and permits the flow of only 207 cubic feet of water