cutting galvanized steel pipe

Cutting Galvanized Steel Pipe (So You Can Repair Any Damage)

If you’ve ever had damage to a water supply pipe made of galvanized steel, you know that it’s not the easiest job in plumbing. The threaded joints make galvanized pipes easy to assemble but complicated to remove.

But if you’re an experienced DIYer with moderate plumbing and pipe-cutting experience, then we encourage you to try this yourself. Let’s get started.

What You’ll Need

  • Two pipe wrenches
  • Pipe tape
  • Either a hacksaw or mini-hacksaw with fine-tooth blade, a reciprocating saw, or a pipe cutter tool (we’ll base our instructions on a hacksaw)
  • Safety glasses to protect your eyes from metal shavings
  • Replacement parts (two lengths of galvanized steel pipe and one union; make sure they are the correct sizes by bringing the old parts to the hardware store)

Cutting Galvanized Steel Pipes – 3 Big Steps!

Keep in mind, once a steel pipe is in place, a threaded pipe cannot be unscrewed as one piece. Why? Because loosening it at one fitting will tighten it at the other fitting.

Also, whenever you’re cutting a pipe, make sure to secure it so it doesn’t twist or bend in the process. A vise grip can help with this. If you can’t use a vice grip, try to prop up the pipe.

1. Removing the Defective Pipe Run

  • Close the main shutoff valve and drain the supply lines.
  • Look for a union near the damaged section and, if there is one, unscrew the pipe from it. Now unscrew the other end from its coupling.
  • Mark the pipe with a pencil where the cut needs to be made. Make sure you place the mark all the way around the pipe so your cutting is accurate.
  • If there is no union, cut through the pipe with the hacksaw and unthread the two pieces from their couplings.
  • To unthread pipe from a union or coupling, grip the coupling with one wrench and turn the pipe with another so that the rest of the run (a run is a length of pipe) will not be twisted or strained.
  • The jaws of the wrenches should face the direction in which force is applied.

PRO TIP: Since galvanized steel pipe is expensive, you might want to save any long, undamaged sections of cut pipe and have them rethreaded by a plumbing supplier.

cutting galvanized steel pipe - mark the cut with pencil
Use a pencil to mark where to cut. Make sure the mark is around the entire circumference of the pipe to ensure a precise, straight cut. If the cut isn’t straight, you’ll need to recut the pipe. Otherwise, you will have an improper fit and leaks.

2. Preparing the New Pipes & Union

  • Buy two lengths of new pipe and a union whose combined length, when threaded together, is the same as the broken seciton.
  • Wind 1.5 turns of pipe tape clockwisse over the threads of the new pipe, tightly enough so they show through.
  • Thread one of the pipes into the nearest coupling using the same double-wrench technique described in the first step.
  • Thread the other pipe into its fitting, leaving a slight gap in the run.
  • Disassemble the threaded union.
  • Slide the union’s ring nut onto one of the pipes, then screw union nuts to each pipe end.
cutting galvanized steel pipe - use a hacksaw
Make sure to stabilize the galvanized steel pipe before cutting. A vice grip can prevent accidental twisting and bending of the pipe.

3. Connecting the Union

  • Slide the ring nut to the center of the union and screw it onto the exposed threads of the union nuts; make sure to join the two pipes.
  • Grip the exposed union nut with one wrench and tighten the ring nut with the second wrench.

You did it! You’re all done cutting galvanized steel pipe and replacing it with new pipe. Congratulations.

cutting galvanized steel pipe - connect union and ring nut
Note how the threads on the steel pipe have pipe tape on them? This creates a watertight seal. Make sure the union is screwed on tight using two wrenches (one tights while the other keeps the pipe from moving).

Final Thoughts

Cutting galvanized steel pipe isn’t out of reach for a DIYer if they follow the above instructions.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help with any of your plumbing pipes and drains.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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