GALVANIZED STEEL PIPE

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.