How to Replace Copper Pipe With PEX

Replace Copper Pipe With PEX Pipe

Lee Wallender

Project Overview
  • Working Time: 1 - 3 hrs
  • Total Time: 1 - 3 hrs
  • Yield: 1 replacement pipe
  • Skill Level: Intermediate
  • Estimated Cost: $30 to $100

Major remodeling projects often involve opening up walls, floors, and ceilings, and this presents a good time to inspect old plumbing pipes and replace them when necessary. Water supply pipes are especially critical to inspect since these carry water under pressure, and the results of a major plumbing leak can be devastating.

Replacing old plumbing pipes is a very common project, and all homes will need to have this done sooner or later. More often than not, the old copper pipes are replaced with newer pipes that are easier to work with: PEX.

From Copper to PEX

At one time, replacing water supply pipes usually meant installing new copper pipes joined with sweat-soldered fittings that required a flame torch and considerable skill to assemble. Copper was the plumbing pipe of choice from the 1950s until 2000 and was widely used both in new construction and to replace the galvanized steel water supply pipes that had been the standard into the 1950s.

But copper's use has gradually faded, due to the introduction of PEX plumbing tubing. PEX is made of cross-linked polyethylene, a form of flexible plastic tubing with cross-linked molecules that create great durability and strength.

While copper pipes and fittings are still common, many professional plumbers now use flexible PEX for all new construction and for most repairs and extensions to existing copper systems. PEX is especially friendly to DIYers, who find the various methods of making connections much easier than soldering copper fittings with a torch.

PEX tubing is typically connected with either crimp-ring connectors, which require an inexpensive specialty tool known as a crimper, or with push-fit connectors, such as the popular SharkBite brand fittings. Both methods can be used to join new PEX tubing to existing pipes, but because push-fit connectors require no special tools, they are a favorite among DIYers.


Watch Now: How to Replace Copper Pipe With PEX

Before You Begin

Copper pipes properly installed have a very long life—50 years or more. In fact, copper excels as a building material. It's still found in roof and chimney flashings. Copper pipes that are green and corroded-looking may not necessarily need to be changed; they just look that way.

Yet copper pipes do go bad eventually. Original copper pipes may be nearing the end of their useful lifespan and it's not always easy to recognize when they need replacement. When copper pipes are just starting to corrode, leaks don't always gush forth and make themselves obvious, but there are early signs you can look for. Any or all of these signs mean that your copper pipe is on its way out.

  • Smell. Over time, you might begin to notice a stale, musty smell that you cannot quite identify. It is even more confusing if the smell is in a laundry room, bathroom, or a child's room because you naturally think that the smell is related to the room. But the odor is more like stagnant pond water, and it persists. The type of smell might be caused by copper pipes leaking within a wall or ceiling.
  • Wall or Ceiling Problems. Wide bulges may start to develop on the ceiling or on walls. This might be due to pinhole leaks in the copper slowly dripping on the drywall, causing it to expand. Water can come from other sources, too. Roofs, gutters, and drainpipes are sources of water within walls and ceilings that are unrelated to copper pipes.
  • Corrosion: If you open a wall or ceiling for some purpose, such as adding insulation, you may notice that copper pipes in the wall or floor cavity have become green, crusty, and corroded. Such pipes may even already have pinhole leaks that are beginning to ooze water but so slowly that dripping is not yet evident.

Learn to identify copper pipe corrosion. Copper pipe joints that were sweated into place by a blowtorch have a braised, burnt, or silvery appearance. This is normal and it is not related to corrosion.

Pinhole Leaks In Copper Pipe
Lee Wallender

What You'll Need

Equipment / Tools

  • Marker
  • Copper tubing cutter
  • Drill-driver
  • Copper pipe deburring tool
  • Tape measure
  • PEX tubing cutter


  • PEX tubing
  • Push-fit straight couplings
  • Push-fit tees (as needed)
  • Copper pipe straps and screws (as needed)


  1. Turn Off the Water

    Water supply pipes are under pressure, and before you work on them you'll need to shut off the water and drain the pipes. There may be branch shutoff valves in your system that will allow you to shut off water only to the section of pipe you are replacing, or you can close the main shutoff valve to shut down water to the entire house during the time you are making repairs.

    Location of Home Water Shut-Off Valve
    Location of Home Water Shut-Off Valve © Lee Wallender
  2. Drain the Pipes

    The water supply pipes will continue to hold standing water and pressure. So drain the pipes by opening a faucet at the lowest level of your home, such as in the basement or a first-floor utility sink or bathroom. This will allow the pipes to drain and prevent mess when you cut into the copper pipes.

  3. Cut Both Ends of the Copper

    Mark the copper pipe to indicate the section you are replacing. Make sure to extend the replacement area well past the corroded area at both ends.

    Using a copper tubing cutter, cut through the copper pipe at both ends of the section to be replaced. A mini tubing cutter is a convenient tool to use in tight quarters.

    Vertical sections of pipe will need to be supported to prevent them from sliding down inside wall cavities. Secure vertical pipes to the wall or floor framing with copper pipe straps and compatible screws before cutting.

    Cut Both Ends of the Copper Pipe
    Lee Wallender
  4. Cut the Fixture Supply Branches

    If the section of copper pipe you are removing includes branch lines running to plumbing fixtures such as toilets, sinks, showers, or bathtubs, you will also need to sever these connections, using the tubing cutter. If these branch connections have been made with couplings or compressing fittings rather than sweat-soldered fittings, disconnect them with a wrench.

    You may want to take this opportunity to replace the copper fixture supply lines with PEX. If so, remove the copper fixture lines, too. Otherwise, leave them in place for reconnection to the new section of PEX tubing.

    Cut Off Toilet and Sink Lines
    Lee Wallender
  5. De-Burr the Cut Ends of the Copper Pipe

    To ensure a good fit with the push-fit connectors, the cut ends of the copper pipe need to be perfectly smooth and clean. Using a copper de-burring tool, smooth the inside and outside of all cut copper pipes.

    Run the tool a couple of inches up the pipe to make sure that all corrosion is removed. Even if you think that the pipe is smooth enough from a visual check, you should still de-burr it with the tool.

    De-Burr Copper Pipe
    De-Burr Copper Pipe © Lee Wallender
  6. Cut a Length of PEX Tubing

    Measure and cut a length of PEX tubing long enough to replace the removed section of copper pipe, using a PEX tubing cutter. Be sure to factor in any length added by the push-fit connectors. Cut the PEX tubing slightly long to allow some room for expansion and contraction. PEX tubing is flexible enough to accommodate some excess.

  7. Connect the PEX to the Copper

    Clean the end of the PEX tubing to remove any burrs or debris. Measure and mark a depth line on the end of the tubing, following the push-fit connector manufacturer's specifications; do the same on each end of the copper pipe.

    Force one end of a push-fit straight connector onto one of the cut ends of the copper pipe. Make sure the pipe is fully seated into the bottom of the connector, and the connector reaches the depth marking. Insert one end of the PEX tubing into the other opening on the straight connector, pushing it all the way to the depth line.

    Repeat with the opposite end of the repair area, joining the PEX to the copper pipe with another push-fit straight connector.

    Connect Each End of Copper With PEX
    Lee Wallender


    If you wish, you can install a push-fit ball valve instead of a straight connector to provide a convenient shutoff for this section of the water supply system. This shutoff valve will remain open most of the time and will be used only if the pipes need to be shut off for future repairs. However, code requires that shutoff valves be located in accessible locations only—don't install a shutoff valve if the wall cavity will be closed up after repairs are made.

  8. Connect the Fixture Supply Lines to the PEX

    Where the removed segment of copper also fed fixture supply lines, you'll now need to connect those supply lines to the new section of PEX.

    This is done by simply cutting into the PEX line with a PEX tubing cutter, then using a push-fit tee-fitting to patch into the line. Two outlets on the tee connect to the PEX line, while the third outlet feeds the supply line running to the fixture.

    If you wish, the copper fixture supply lines can also be replaced with PEX at this time.

    Replace Branch-Outs To Toilet, Sink, Shower/Bath
    Lee Wallender

3 Levels of Copper-to-PEX Pipe Replacement

When you run into corroded or leaking copper pipes during your remodeling projects, you have several gradations of DIY options, from easiest and least expensive to most difficult and expensive.

Spot Repair the Copper With PEX

When you find leaking copper pipes, you can take the bare minimum approach, cutting out the bad section and replacing it with PEX. Often, you can get by with installing just a single push-fit connector in that area. Copper pipe spot repairs are frequent with any older home.

Replace Visible Sections of Copper With PEX

As a compromise between complete re-piping of the entire house and small patches, you can replace large sections (10 feet or longer) of exposed copper pipe with PEX, branching out where needed.

Replacing visible runs is the solution many DIYers choose because this method is not as ambitious nor costly as re-piping the entire house. While it may sound complicated, this option is actually not much harder than the spot-fix option. That's because you're extending the pipe as far as possible rather than simply localizing the repair.

Replace All Copper With PEX

Cost aside, the best long-term solution is to re-pipe your entire home, replacing copper pipes with PEX. This involves disconnecting and bypassing all your existing copper and running new PEX lines throughout the house. You can either follow the current pattern or start anew with a PEX manifold-and-branch system. As a side project of replacing metal pipes with PEX, you'll need to re-ground your electrical system.

Make Sure Your Electrical System Is Grounded

One byproduct of changing out your metal plumbing pipes for PEX pipes is the loss of a ground for the home's electrical system.

In homes with older electrical systems, the electrical system is sometimes grounded through metal water pipes. This is not a common practice with circuit breaker systems, which are usually properly grounded when they are installed, but it is more common in older systems that are protected by fuses rather than circuit breakers.

When replacing metal water pipes with PEX, this continuous grounding path may be interrupted, since plastic piping is not an electrical conductor.

In addition, codes in some communities may require that the entire plumbing system be bonded to the home grounding system. Here, too, replacing copper with PEX may interrupt that bonding. Consult local code authorities for instructions on how to handle bonding with plumbing systems using PEX.

For this reason, it is a good idea to check to make sure your system is still properly grounded whenever replacing metal plumbing pipes with plastic. If you find that outlets have lost their grounding connection, consult an electrician to reestablish grounding. Normally this is done by connecting the main service panel to a grounding rod driven into the earth, via a bonding wire.