Burying Copper Pipe

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by dgale, Mar 5, 2011.

  1. dgale

    dgale New Member

    Messages:
    6
    Location:
    Arcata, CA
    I am running hot and cold water lines from my house to our detached studio apartment and about 20' of the run needs to be buried across the yard between the house and studio. My plan is to dig a trench about 16" deep, add about 4" of pea gravel, places the pipes, add more pea gravel, and then fill the rest with soil. I'm planning to use 3/4" schedule L rigid copper pipe and am just wondering foilks' thoughts on this approach? None of it will be buried under concrete or otherwise be obstructed from easy excavation if I needed. I live in far-northern coastal California (near Eureka) where it is really wet all winter and spring but rarely do we get more than a mild freeze. The hot water will be provided from the tankless hot water heater in our house, which is sized large enough to handle all of the load.

    Any issues anyone can see with any of this? I'm planning to insulate the pipes where they are exposed above ground but otherwise just simply bury them in a bed of pea gravel where underground. Any thoughts, suggestions etc. on this would be appreciated.
  2. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    I sure wouldn't bury hard temper (rigid) type L copper in gravel. Maybe in a sand bed but never in gravel. I'm not sure but it may be a code requirement that all buried copper piping be type K soft temper.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,003
    Location:
    Bothell, Washington
    You can bury type M copper pipe and L will be even better.
    Joints in dirt can be lead free, joints under slabs are silver soldered.
    Water lines should be six inches below the frost line. That varies by climate zone.
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    Consider insulating the hot water line so the ground doesn't wick away the heat.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    You CAN make joints in copper underground outdoors, but I would not recommend it unless there is no other way to install the tubing. We ALWAYS use soft copper for underground work so we do NOT have to make joints, unless there is a tee junction.
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,246
    Location:
    Land of Cheese
    While copper is fine, you might ask what the advantage is of using it instead of PEX or PVC.
  7. dgale

    dgale New Member

    Messages:
    6
    Location:
    Arcata, CA
    Burying Copper Pipe Follow-up questions

    Thanks for all the input - as far as insulating the hot water pipe underground, any advice on how to best do this? I typically use the slip-on foam insulation under my house, but wonder how well this stuff would hold up buried? Is this the best stuff to use underground or is there a preferred insulation out there for burying?

    As far as type K vs L, I already have a bunch of type L rigid and type K is expensive, so I'd prefer not to go this route unless it's really deemed necessary (?) - I've seen conflicting advice on what's allowed/best. Is it a concern about ground movement and type K will obviously be more flexible? I figured the pea gravel would help with this, as well as reducing water accumulation around the pipe. Someone suggested sand and I could certainly put a bed of gravel in for drainage and then surround the pipes themselves in sand to reduce movement potential. Thoughts? I don't mind buying the type K if it's really the way to go and folks think type L rigid is a mistake. What sort of fittings do you use on the flexible stuff? I'd need to connect it at both ends to type L rigid and have never worked with the flexible stuff.

    As far as having joints underground, I would need to have a few elbows buried but no connectors - what is the concern about buried joints? Are they somehow more prone to leaking when buried or is it just the fact that they are buried and you have no way to know if they did start leaking?

    Sorry to bombard with questions but I want to get it right the first time so I don't find out later I didn't do my homework and made a mistake.
  8. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    Since it doesn't appear the pipe would be subject to crush pressure, you could probably get away with the closed cell foam insulation used indoors but I would tape over it with red tuck tape. I like to case some stuff inside Big "O" corrugated pipe for crush resistance.

    The guys that pipe outdoor wood burners use an insulation thats made specifically for direct burial but that stuff's expensive. There is a similar product for a single waterline to draw from a lake but that too is expensive.
  9. dgale

    dgale New Member

    Messages:
    6
    Location:
    Arcata, CA
    Just so I'm clear, what is "red tuck tape"? I usually use gorilla tape (basically a heavy duty duct tape) with the closed-cell foam insulation, wrapping it every 4' or so just to make sure it stays on over time. Not sure if this what you mean when you say wrapping it? I'm also not sure what "Big O corrugated pipe" is? I do have some leftover 3" flex pipe (the kind you use in a french drain) that I could slip the pipe into I suppose. There's not much risk of crushing it at this point but you never know down the road where someone else will drive etc. that could cause crushing. Would buried flex pipe offer much additional crush resistance in this case? I could also just get some 3" or 4" PVC and put the pipes inside them?
  10. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    Sorry, Tuck tape is a Canadian manufacturer of tapes and they make the red contractor's sheathing tape that we are all familiar with north of the border. It has a super adhesive and has replaced Duck tape where a more permanent fix is needed. Around here, Duck tape is used like Gaffer tape and meant to be non-permanent. We don't call it "duct tape" because we don't use it on ducts as it will dry out and fall off. Duct tape is a metal foil tape that has similar adhesive characteristics to Tuck tape.

    Big "O" might be more regional nomenclature. It comes either slitted for French drains, or unslitted. I do sometimes use PVC pipe as well. There is an inexpensive 4" without holes that's used to pipe out to septic fields but for crush resistance, I use the sched 40. For inexpensive 2", I use the stuff made for central vacs but it doesn't have the crush resistance of sched 40.
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