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Thread: Detached garage plumbing

  1. #1

    Default Detached garage plumbing

    I have a few questions about plumbing a new detached garage.
    First off, I'm dealing with existing construction...slab already in place and walls completely framed and complete. This is a new home im purchasing...otherwise I would have planned this all advance. I will be installing a slop sink, house bib and possibly a small water heater to start. Might also add a half bath in the future as well.

    My questions deal with domestic water supply to the garage from the house:

    1. In the trench from the house to the garage, can I run my cold water piping in this same trench with my plastic electric conduit feed to the garage sub panel?

    2. What type of piping should I use? Copper, Pex, PVC?

    3. What diameter should the pipe be? (100' run from the house)

    4. How should I stub the pipe up into the garage? Should I dig under the foundation and cut the concrete inside the garage and bring it up that way to protect from freezing?

    5. What do I use to protect the pipe through the concrete stubout if #4 is allowable?

    6. How deep should I trench? (New York...cold winters)

    Thanks,
    Jon

  2. #2
    Master Plumber Redwood's Avatar
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    I have 1 question before we go anywhere...
    Is the garage heated?

  3. #3

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    I have 1 question before we go anywhere...
    Is the garage heated?
    Yes, eventually but I probably won't keep the heat on all winter.

    I was planning on including valves to drain the pipes, etc.. if I do plan on turning the heat off...Thoughts? I like to do things right the first time rather then change things down the road (i.e...when the time comes and I add heat to the structure)

    My concern with the piping at this point is basically because I'll have a trench open for the electric run. I'd hate to have to dig again in the future.

    Thanks,
    Jon
    Last edited by zimzimma; 08-17-2008 at 09:52 AM.

  4. #4
    Master Plumber nhmaster's Avatar
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    Most plumbing codes won't give a rats rear if there is electric wires in the trench but the Electric code shure as hell does. Can't do it.

  5. #5

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    Most plumbing codes won't give a rats rear if there is electric wires in the trench but the Electric code shure as hell does. Can't do it.
    Ok, I'll have to check into that...thanks. I've read that as long as you maintain 12" in the trench between the 2, that its ok??

    How about the other questions? Do I have all you professionals stumped?

  6. #6
    Engineer Furd's Avatar
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    How do you plan to get rid of the used water? Supply piping is easy, drainage is much more difficult.

    Your supply piping (and drainage) needs to be buried beneath the frost line in your area. That could be several feet deep if you have severe winters. The depth of the electrical may under certain circumstances be as shallow as 6 inches or as deep as 24 inches or more. Furthermore, local code will dictate the required depth of both water (supply and drainage) and electrical so you need to determine your "Authority Having Jurisdiction" (AHJ) and they will be able to give you the local requirements.

    You may also want to consider additional conduits for telephone, Internet and television cables. These low-voltage cables may NOT run in the same conduit as power cables and should be separated from power by a minimum of 12 inches.

    As for the required size of the water supply...it kind of depends on what you are going to be using the water for. If all it is for is hand washing and rinsing latex paint from brushes then a 1/2 inch pipe will be adequate. If you want to use it for fire protection sprinklers then it will need to be a whole lot bigger.

  7. #7
    Master Plumber Redwood's Avatar
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    Drainage does not have to be below the frost line as it drains dry after use.
    Supply however does check with your local authorities as to the required depth. Here it is 48".

  8. #8

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    For the immediate time being, all that I will have at the garage building will be a slop sink and hose bib. I have a drywell near the garage that was for the washing machine...(new drywell was installed on other side of house for it) I plan to use the old drywell for the sink water. When the bathroom becomes a reality, ill probably have a new pool installed and have a professional rough in the waste plumbing to it.

  9. #9
    Master Plumber Redwood's Avatar
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    I would suggest a discussion with your local building inspector about your drainage plans.

  10. #10

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    I would suggest a discussion with your local building inspector about your drainage plans.
    Ok, and the curious one now asks, Is there a problem with running a sink into a drywell?

  11. #11
    Master Plumber Redwood's Avatar
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    Here there would be.
    A code upgrade would be expected.

  12. #12

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    ok, thanks...thats why I asked.

    Getting back to my original question, How do I protect the copper at the stubout in the garage when I plan to re pour the concrete?

  13. #13
    Master Plumber Redwood's Avatar
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    Well if you are not going to have heat I would recommend a curb stop that will allow drain down out side the building. Then pitching all pipes back to that point.

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