How to Join Pex Pipe to Galvanized Fittings

Written by markt
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How to Join Pex Pipe to Galvanized Fittings
Easy-to-use PEX can be connected to old galvanised pipe (scissor cut white plastic pipe image by Graf_es from

While galvanised pipe isn't used to build new plumbing systems today, many older homes still contain working galvanised pipes. Cross-linked polythene pipe (PEX), an easy-to-install alternative to copper and PVC pipe, can be connected to galvanised pipe; new PEX lines can therefore be added to an older galvanised pipe system. PEX is lightweight and flexible, making it ideal for running new water lines through existing floors and walls, and it withstands freezing extremely well.

Skill level:

Things you need

  • PEX/PVC clamping pipe cutter
  • PEX push-together transition fitting with threaded connector (like GatorBite or SharkBite)
  • PEX fitting release tool
  • Emery paper or very fine sandpaper
  • Ruler
  • Felt-tip pen
  • Pipe joint compound
  • Pipe wrench
  • Wire brush

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  1. 1

    Choose the correct type of PEX transition fitting. The fitting for this connection has a push-in side for connecting the PEX pipe, and a threaded side for connecting the old galvanised pipe. Galvanised connections consist of a male side (also called the nipple) that is screwed into the female side (also called the union). If the galvanised pipe has male threads, use a female-threaded PEX transition fitting. If the galvanised pipe has female threads, use a male-threaded fitting.

    How to Join Pex Pipe to Galvanized Fittings
    In this old galvanised pipe connection, two male pipes (at left and right) are joined by a connector with two female sides (at centre) (rusty metal pipe 2 image by jbattx from
  2. 2

    Clean the galvanised pipe threads. Use a wire brush to clean the threads of the old galvanised pipe, to ensure a tight connection.

  3. 3

    Apply joint compound. If the galvanised pipe has male threads, apply the compound to the galvanised pipe, and use a female-threaded PEX transition fitting. If the galvanised pipe has female threads, use a male-threaded PEX transition fitting, and apply the pipe compound to its threads.

  4. 4

    Screw the galvanised pipe and the PEX transition fitting together, and tighten the connection with the plumbing wrench.

  5. 5

    Cut the PEX pipe to the required length using the PEX clamping pipe cutter. Make the cut as square as possible and perpendicular to the length of the pipe. This will ensure a tight connection with the PEX transition fitting.

  6. 6

    Lightly sand the edges of the PEX pipe with emery paper to remove any burrs or jagged points. Do not over-sand.

  7. 7

    Use the ruler and pen to make a mark on the PEX pipe 1 inch from the cut you made, indicating how far down the pipe you need to push the fitting. This distance may vary depending upon the brand of fitting--double-check the fitting's specifications to make sure you use the right distance.

  8. 8

    Holding the PEX transition fitting firmly, take the end of the PEX pipe and push it firmly into the other side of the fitting until its edge reaches the pen mark. This indicates that you've made a full connection between pipe and fitting.

  9. 9

    Turn on the water to the line and check for leaks. If the PEX transition fitting leaks, shut off the water and use the PEX fitting release tool to remove the fitting from the PEX pipe. Make sure the edges are clean and square, re-sanding lightly if needed, then push the PEX pipe back into the fitting.

Tips and warnings

  • Check local plumbing codes before beginning any home plumbing job, and obtain any required permits.
  • If you're working on an active water line, shut off the water and drain the line before beginning.
  • Never use PEX for above-ground exterior lines, as UV rays from sunlight will quickly ruin its integrity.

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