proper way to make up a right and left coupling is as
follows:

[Illustration: FIG. 69.--_F_ reads center of ell to end, _C_ reads
center of ell to center of valve, _D_ reads center of valve to
center of T, _E_ reads center of T to center of ell.]

Screw home the coupling on the right thread. Mark with a piece of
chalk on the coupling and the pipe showing a point on each where
the coupling makes tight. Take off the coupling and count the turns
and make note of the number. Now do the same on the left thread
and make a note of the number of threads. If the left thread has
six turns and the right has four and one-half, then to insure that
the left thread will be tight when the right thread is, the
coupling must be put on the left thread one and one-half turns
before it is started on the right thread. Now with four and
one-half turns, the right and the left threads will both be tight.
A little thought and practice will make this connection clear. If
all the measurements in this exercise are not cut accurately, the
right and left coupling will not go together.

CHAPTER XIII

COLD-WATER SUPPLY. TEST

The supplying of cold water to buildings and then piping it to the
various fixtures makes a very interesting study. We have gone over
the methods of laying and piping for the house service pipe. We
will go over the different systems now employed to supply the
water, quickly.

UNDERGROUND WATER.--In thinly populated districts the well is still
employed to supply water to the building. The water is brought to
the surface by means of a large bucket or by means of a pump. A
well point can be driven into the ground until water is reached and
then the water can be brought to the surface by means of a pump
operated by hand or by power. The water can be forced to a tank
that is open and elevated, or forced into a tank that is closed and
put under pressure. From either tank the water will flow to any
desired outlets. A windmill can be employed to furnish power to
operate the pump. Water supply that is received directly from
underground is by far the best to use. A cesspool or outhouse must
not be allowed on the premises with a well, otherwise the well will
be contaminated and unfit for domestic use. An open well is not as
sanitary as a driven well, as the surface water and leaves, etc.,
get into it and decay and pollute the water, and soon make it unfit
for domestic use.

STREAMS AND BROOKS.--The brooks and streams fur