Hot water heater in/out line sizes

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jjvb, Jun 19, 2006.

  1. jjvb

    jjvb New Member

    Messages:
    5
    I need to replace an electric hot water heater. It is on a farm with a well. The water pressure is never very high. I need to gather all the materials then drive 3 hours to do the replacement. I am not sure of what I will find other than the existing lines are a mix of galv and copper of various sizes. I will use Pex as the crawl space is brutal (dirty and cramped). It has one bath, one kitchen sink and a wash machine.

    My question is what size of cold water inlet would be sufficient? Would 1/2 inch be large enough? I am planning on using 1/2 on the outlet side.

    Thanks.
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    1/2" PEX would give you very unsatisfactory results. It has a small ID. If this were copper, I would use 3/4, and for PEX 3/4 would definitely be the minimum.
  3. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You could use 3/4" CPVC. It is a little larger than PEX in same size designation and is a lot easier to work than copper. The only problem is that you have to wait a while for the cement to achieve full strength.
  4. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    On a well, running PEX, I would go with 1", if possible for good flow, but a minimum of 3/4" like jimbo said.
  5. jjvb

    jjvb New Member

    Messages:
    5
    Thanks for the replies. Looks like I had better stick with at least 3/4 copper. I just measured some Pex and 3/4 is not really 3/4 is it. So what does the CST refer to anyway? I should probably try to go with 1", but I've not seen 1" Pex anywhere. Or 1" copper for that matter. Not sure that I want to dabble in CPVC right now.
  6. jjvb

    jjvb New Member

    Messages:
    5
    OK, as long as I am going to work on this system, I have another question. The house in question is my moms. If you are in the shower, and somebody uses cold water anywhere in the house, you get some pretty hot water in the shower. What would be a way to solve this problem? Thanks again.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,348
    Location:
    New England
    All new shower valves are required to have what is called a pressure balance valve. This basically throttles down the hot water if the cold water pressure drops, basically keeping the relative volumes the same. It is also called an anti-scald valve. Some of them also can be had with temperature control that automatically adjusts the volumes to keep the same temperature. It really helps as the hot water tank gets drained, but it won't work miracles.
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