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Thread: Copper water supply line limitations?

  1. #1

    Default Copper water supply line limitations?

    Is there a restriction on how far I can run a 3/4" branch off of my existing 3/4" copper water supply lines? The most convenient place to solder in a tee will require me to run an additional 30-40 feet of copper to get to where I need to be. I assume it's ok, since this is all in the basement. Even though the dist to the 2nd floor is much less, I have to believe running against gravity is worse than the 20 extra feet my extension will have to run. I currently have about 3.5 baths and am adding a 4th full in the basement.

    Also, are their limitations to the types of fittings you can use in running copper supply lines? I need to snake around the perimeter of my room, which requires 4-5 90 deg turns. Any risk of pressure loss?

  2. #2
    In the Trades Gary Swart's Avatar
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    I don't think you will have a problem with pressure loss, but you turn on the hot water, you will have a very long wait and waste a lot of water purging the lines of cold water. I'd suggest you put you tee where you will have the shortest pipe runs and that you reconsider the 3/4" size. I made that mistake once and regretted it to the point of replumbing with 1/2".

  3. #3

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    Thanks for the tip. The problem is the whole bathroom needs to function off the branch. I'm not sure 1/2 is advisable as a group main, is it?

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    In the Trades Gary Swart's Avatar
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    Suggestion. Go to the home page of this site. Find the Replacing Pipes link. Under that is another link on pipe sizing. I think this might answer your questions.

  5. #5

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    thanks for the link. I am having trouble understanding the table.

    I have a total of 46 fixture units.

    What does a 'developed distance of 80 feet' mean?

    If I have 3/4" street service and 1" in the house, does this mean I can only have 34 fixture units total? Or does it mean that the water pipe/pressure can only support 34 fixture units of 'load' - or simultaneous use?

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    Quote Originally Posted by prashster
    thanks for the link. I am having trouble understanding the table.

    I have a total of 46 fixture units.

    What does a 'developed distance of 80 feet' mean?

    If I have 3/4" street service and 1" in the house, does this mean I can only have 34 fixture units total? Or does it mean that the water pipe/pressure can only support 34 fixture units of 'load' - or simultaneous use?
    Developed distance is the lengths of the individual pipes plus a factor for each fitting, the most common one being adding about 10 feet for each elbow. The fixture count tables does not consider all simultaneous use. It is also weighted to the way water would typically be used, i.e., the more faucets, etc., in the building the less chance that all would be on at the same time.

  7. #7

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    Ok, thanks, HJ. I infer from the table that I can only have a max of 36 fixture units.
    I'm adding a bathroom and utility sink that will push the load to 46. Does this mean I need to upgrade my copper water main line? It's hard to believe, since I live in a 'big box' developer house, and most of the other homes in my development have more bathrooms than I do, yet they all have the same water supply size.

    Confused.

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