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Thread: how long for dirt to settle in sewer pipe trench

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    DIY Senior Member DanMcD's Avatar
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    Default how long for dirt to settle in sewer pipe trench

    A trench (70 feet long by about 4 feet wide) was dug for my sewer line replacement (from the house to the street). It varied in depth from 3 to 10 feet. When they backfilled the dirt, they did not compact it. I now have from 1 to 3 feet of dirt above my grass level that will need to settle over time.

    Do most plumbers compact the soil or just push the dirt back in the hole?

    Does anyone have any experience on how long it may take for this dirt to settle?

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    Moderator & Master Plumber hj's Avatar
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    I don't compact the soil, but all you have to do is run water into the ditch and it will settle the dirt. You can speed up the process by shoving the running hose down into the soil. Your plumbers must have been the sterotypic 350# guys to need a 4' wide trench. I usually dig mine 18" to 24" wide.
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    IBEW Electrician big2bird's Avatar
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    1) What kind of pipe?
    2)Did they use sand around it?
    3)My hip shot guess is 6" max in 6 months,.

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    IBEW Electrician big2bird's Avatar
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    Quote Originally Posted by hj View Post
    I don't compact the soil, but all you have to do is run water into the ditch and it will settle the dirt. You can speed up the process by shoving the running hose down into the soil. Your plumbers must have been the sterotypic 350# guys to need a 4' wide trench. I usually dig mine 18" to 24" wide.
    Water jetting works okay with sandy soil. Clay, not so much. Must be pretty loose to have that much of a mound.

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    Moderator & Master Plumber hj's Avatar
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    quote; 1) What kind of pipe?
    2)Did they use sand around it?

    What does the kind of pipe have to do with the soil settling.
    The only thing that would make sand or not relevent, is that it would take up some room in the ditch and need less dirt to backfill it. I usually use copper, and backfill with what I excavated. We water soak sand, clay, or dirt, and they all settle down.
    Licensed residential and commercial plumber

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    IBEW Electrician big2bird's Avatar
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    Quote Originally Posted by hj View Post
    quote; 1) What kind of pipe?
    2)Did they use sand around it?

    What does the kind of pipe have to do with the soil settling.
    The only thing that would make sand or not relevent, is that it would take up some room in the ditch and need less dirt to backfill it. I usually use copper, and backfill with what I excavated. We water soak sand, clay, or dirt, and they all settle down.
    You use copper for sewer mains?
    I ask for two reasons.
    8' of dirt dumped on plastic without a sand bed will crush, distort,kink.
    If they did use sand, he has excess dirt that will never settle.

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    DIY Senior Member DanMcD's Avatar
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    hj,

    They used a backhoe type machine to dig the trench...and you are right...more like 18 to 24 iches wide as I re-look.

    The pipe was the green/blue sewer pipe SDR 35. The backfill was some type of fine gravel...then they put the dirt on top of that.

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    IBEW Electrician big2bird's Avatar
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    Good news is the pipe will be fine. Whatever volume of gravel they brought will displace the dirt needed.

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    Moderator & Master Plumber hj's Avatar
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    quote; You use copper for sewer mains?

    Sorry, I was thinking of water line when you asked about the material, since I only think of plastic when it comes to sewer lines, and then I only consider sch. 40 material. So, "what did you use for the pipe" is somewhat immaterial.
    .
    8' of dirt dumped on plastic without a sand bed will crush, distort,kink.

    That would not happen with sch. 40 ABS or PVC, but now that I know it is SDR 35, that CAN happen.

    quote; The pipe was the green/blue sewer pipe SDR 35.
    Good news is the pipe will be fine

    The bad news is that they used SDR 35. IF I were to use it, and I NEVER do, it would only be buried less than 4' underground. I have dug up innumerable SDR 35 sewers, at least 3 in the last few months, which were collapsed, split, and/or "ovalled" because of the pressure of the ground above them.
    Last edited by hj; 11-28-2012 at 03:26 PM.
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    DIY Senior Member DanMcD's Avatar
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    The plumber told me the State/County dictates to them the type of pipe to b used. In this case I'm, in Ohio, Greene County. So, it makes no sense to me that a licensed plumber and the State/Country would allow the use of a pipe that might get crushed under the weight of the dirt.

    Before the plumbers buried the pipe with the dirt, the County inspector came out to review the work. At that point, there already was some gravel around the pipe but it was not completely covered. You could still see the top of the pipe and any joint connections.

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    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    The State/County dictates the minimum that can be used. SCH 40 would have been the better choice. The cost difference is minimal.

    John

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