Replacing old water supply plumbing questions

Discussion in 'Plumbing Code Questions' started by Nick16, Jul 26, 2020.

  1. Nick16

    Nick16 New Member

    Jul 26, 2020

    I'm currently replacing my old steel water supply plumbing (I believe it's 1/2 in) with expansion Pex-A (1 in). I'm copying the exact same plumbing network that's already there, and currently measuring/cutting pipe and putting in fittings. Then I will hang/attach everything on the final day. I don't have much plumbing experience, and have spent about 4-6 hours researching generals through articles/youtube videos and have two questions.

    1) Looking at the line coming from the water-main into the house, this piece is on the pipe. I'm not sure if it's important, or just a joint added because they needed to extend the pipe. Is this something I should know about when putting in my new pipes? Picture attached. Just don't want me inexperience to bite me in the butt!

    2) When connecting my new pipes into the water main line coming through my wall from the meter outside, is there anything I need to be aware of aside from ensuring everything is attached correctly with a valve? I spoke with a friend a while back who did a similar thing in his house but with copper, and he mentioned hiring a plumber to attach the main line, but I'm not sure if that's necessary or not.

    Thank you for the help!


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    Last edited by a moderator: Jul 26, 2020
  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    The new pipe or fitting should thread into that.

    The kitchen sink gets it's own 1/2" lines H&C
    The washer should get 1/2"
    A bathroom gets 1/2" on the hot and 3/4" on the cold because you're adding a toilet.
    The water heater gets 3/4" going in and out.
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  4. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    That is a union.

    If that is on a steel pipe, you will be removing that too.
  5. Helper Dave

    Helper Dave In the Trades

    May 25, 2020
    I'd say definitely hire a plumber if you were redoing at the meter, but if yours is outside, and you're only replacing inside pipe, you should be fine so long as you know what you're doing.

    What size is your meter, and the pipe coming into the house, though? Hopefully not just 1/2". Upsizing too much can reduce your pressure.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    Upsizing, by any amount, NEVER reduces the pressure.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    One of the advantages of using pex is that it bends, so you can eliminate most of the fittings to change direction versus say copper or galvanized piping. It's a waste of materials to use lots of fittings to change direction. There is a limit on how tight of a bend you can make, and, if one is required, you may want to use a bend support which will give you a reliable, minimum radius right-angle bend without kinking.

    To keep it looking somewhat neat, you do want to/need to use appropriate hangers for it.

    People often confuse volume with pressure. A soda straw 1/4" line will have exactly the same pressure as a fire hose at static (no flow)...the smaller pipe will have a lot more friction, so there will be pressure loss along its length as it tries to flow faster. Now, if you use a nozzle, the water will try to accelerate through the restriction, but it would slow down again after it passes, or stay the same if, for example, it was coming out of a hose.
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