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About Your
Plumbing
Steel pipe, which is galvanized, was originally
used in plumbing installations. If you use galvanized steel
pipe in an installation, you should use no less than the
3/4 inch size, and no less than the size of the pipe in
the original plumbing. This avoids the possibilitv that
the installation might cause an excessive pressure drop,
resulting in a reduction of flow. As always, local codes
should be followed.To make an installation with galvanized
pipe, the following tools will be needed: pipe, wrenches,
a pipe vise, pipe cutter, reamer, dies for cutting threads,
a level, thread dope, pipe joint cement or pipe thread tape.
Pipe Measurements
In order to "come out even," an installer
must he able to figure lengths for the piece of pipe to be
used in running from one point to another. To do this, allowances
must be made for the length of threads, the size of the fittings.
etc.Each size of pipe has a set of specifications to cover
all fittings available. For example, with 3/4" pipe,
the standard thread engagement for all fittings is 9/16".
This means that when a length of pipe is tightened securely
into a fitting, 9/16" of the length of pipe will be inside
the fitting. In other words, the pipe must be 9/16" longer
at each end than the measurement between the faces of the
fittings. Consider an installation where the pipe runs vertically,
then horizontally for five feet, and then back down again,
60" between the centerlines of the two vertical pipes.To
calculate the length of the horizontal piece of pipe, first,
figure the fitting allowance for an elbow. This is the distance
between the end of the pipe, inside the elbow, and the intersection
of the centerlines of the two pipes. Do this by checking the
specifications and determining the standard dimension of an
elbow for the distance between the intersection of the centerlines
and the face of the elbow. The fitting allowance is 3/4".
The length of pipe must be reduced by 3/4" for each elbow
that is included in the five-foot run you are making. This
is because the distance from the end of the pipe, inside the
fitting, to the intersection of the centerlines is actuallv
3/4".Since there will be two elbows, subtract 1-1/2"
(2 x 3/4") from the theoretical 60'' run, which makes
the pipe length for cutting 58-1/2" long. Each end will
be threaded 9/16" into each of the two elbows. Follow
the same procedure for all fttnngs to determine actual
lengths of pipe.
Cutting
Pipe
Although it is possible to make cuts that are
"square" or perpendicular to the centerline of the
pipe with a hack saw, pipe is easier to cut with a pipe cutter.
In order to properly thread galvanized pipe, a square cut
is necessary. When cutting pipe and when cutting threads with
a die, a pipe vise should be used to hold the pipe. After
cutting the pipe, the end should be reamed so that the inside
diameter is full size and no burrs remain.When cutting threads,
cutting oil should be applied three or four times. This reduces
the heat which is generated by the cutting die and prevents
threads from being torn. It also keeps the dies from becoming
dull prematurely. When the end of the die is even with the
face of the pipe, the threads are cut to standard length.Before
engaging threads in the fitting, they should be cleaned of
chips and burrs and then wrapped with pipe thread tape or
coated with pipe dope (pipe joint compound). Only the male
threads should be coated.
How To
Tighten A Fitting
Engage the threads of the pipe and the fitting
and tighten by hand until they are tight. Then place a wrench
on the bead of the fitting and turn about one turn. Two turns
may possibly be required, but no more. PIPE OR FITTING GOUGING
CAN BE MINIMIZED BY NOT CHANGING THE POSITION OF THE WRENCH.
Too much tightening may expand a fitting so that it will leak
and have to be replaced. Brass fittings are more likely to
expand than steel fittings. Use a wrench that is properly
sized for the diameter of pipe being installed. |
