My water heater is hard-plumbed with galvanized pipe. It is at least 20 years old and is leaking:


I want to use modern flexible hose for the new water heater, but I don't know the best way to change the existing setup. I could simply take off the unions and try to thread adapters to the pipe stubs, but I'm concerned that the existing threads will have corroded to the point where it won't make a good connection.

How should I proceed?

  • 2
    The pipes do not look at all like the threaded joints would have corrosion to the extent that you would not be able to take them apart. Best part of things here is that each pipe does have a decoupling union, including the pressure relief valve overflow line.
    – Michael Karas
    Commented Mar 27, 2017 at 3:53
  • 2
    @MichaelKaras - This seems like it should be in an answer as it directly responds to the asker's question.
    – William
    Commented Mar 27, 2017 at 4:01

2 Answers 2


Keep the unions.

If (as seems unlikely, given the over-all condition, despite one differing opinion) you can't get the pipe out of the old union-half, go purchase two new half-unions (or complete unions if you can't source the correct half-unions alone - take the half-union you remove with you to the store to match it) and connect your flex-hose to the half-union. Otherwise just unscrew the pipe from the half-union and screw in the new flex hose, or any adapters you need to connect to the flex-hose.

  • You can't match half unions, so don't wast your time going to the store
    – d.george
    Commented Mar 27, 2017 at 16:30

You will not know the actual condition of the pipe until you take it apart. Galvanized pipe deteriorates from the inside out, due to friction of the water with the metal pipe. Galvanized pipe hasn't been used for many years. Before you take the piping apart, have a phone number of a local plumber handy. This could easily become a nightmare of a job.

  • Good point, but doesn't answer the question about making new connections.
    – isherwood
    Commented Mar 27, 2017 at 15:18
  • The answer is easy. If you have never screwed around with very old galvanized piping, or you don not have the proper tools find a friend , buddy or company that can help you. Other than that, go to home depot or lowes get an installation kit for a water heater that has flexible tubing, break the unions (take apart), or cut the pipe and take apart the piping until you get to a good section of thread and follow the directions on the package. It is not hard to do. Just take your time
    – d.george
    Commented Mar 27, 2017 at 16:39
  • Seems like that should be part of your answer.
    – isherwood
    Commented Mar 27, 2017 at 16:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.