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  • Grading Trenches

    Just asking for some of the forums thoughts on grading plumbing trenches after mechanized machinery has made it's pass.

    What is your technique?
    Do you like to use domestic soil?

  • #2
    Re: Grading Trenches

    I use a philly rod and dumpy level then compact the bottom of the trench. I have 6" of sand all around the pipe and bring the level up from there. What's domestic soil?
    Buy cheap, buy twice.

    Comment


    • #3
      Re: Grading Trenches

      Originally posted by drtyhands View Post
      Just asking for some of the forums thoughts on grading plumbing trenches after mechanized machinery has made it's pass.

      What is your technique?
      Do you like to use domestic soil?
      The best way is this:

      1) Know the I.E. (invert elevation or lowest surface of your pipe) of the pipe you are connecting to.

      2) Determine the elevation of the rough-in of your lowest fixture.

      3) Calculate the distance between the two.

      4) Add in the lose of elevation depending on the slope.

      5) If it will work mathematically, determine weather you are using sand (recommended) or native soil.

      6) If it will not work, RFI the engineer, stop the project until this is clarified. If there is civil plans drawn, do not spend valuable backhoe time potholing what engineers should have verified.

      7) If it does work, set up a laser level, set it at the invert of your starting elevation (the lowest fixture's starting elevation). If you are using sand, raise the receiver up to the amount of sand you intend to use.

      8) Check the trench every 10' by moving the receiver up 2-1/2" (for 2% or 1/4" per foot) or 1-1/4" (for 1% or 1/8" per foot).
      the dog

      Comment


      • #4
        Re: Grading Trenches

        Originally posted by plumbdog10 View Post
        The best way is this:

        1) Know the I.E. (invert elevation or lowest surface of your pipe) of the pipe you are connecting to.

        2) Determine the elevation of the rough-in of your lowest fixture.

        3) Calculate the distance between the two.

        4) Add in the lose of elevation depending on the slope.

        5) If it will work mathematically, determine weather you are using sand (recommended) or native soil.

        6) If it will not work, RFI the engineer, stop the project until this is clarified. If there is civil plans drawn, do not spend valuable backhoe time potholing what engineers should have verified.

        7) If it does work, set up a laser level, set it at the invert of your starting elevation (the lowest fixture's starting elevation). If you are using sand, raise the receiver up to the amount of sand you intend to use.

        8) Check the trench every 10' by moving the receiver up 2-1/2" (for 2% or 1/4" per foot) or 1-1/4" (for 1% or 1/8" per foot).
        Dog great explanation.Actualy got busted once for flat venting a few w/c at the end of a grocery store waste system that I had the 4" running at 2%.

        How many use native soil to "tune" you ditches.

        Comment


        • #5
          Re: Grading Trenches

          Originally posted by gear junkie View Post
          I use a philly rod and dumpy level then compact the bottom of the trench. I have 6" of sand all around the pipe and bring the level up from there. What's domestic soil?
          It was a term a couple of soils engineers used a while back on a job.I thought it would make me thound edukaded,wadya think

          Comment


          • #6
            Re: Grading Trenches

            Adam,

            When ever possible I like to shade my trench with sand. It gives you a much better bedding and keeps the rocks away. Just make sure you include it on your bid.

            Mark
            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

            I never lost a cent on the jobs I didn't get!

            Comment


            • #7
              Re: Grading Trenches

              I use "native soil" unless it is unsuitable (rocky etc...)
              If unsuitable, I use sand for bedding...

              Comment


              • #8
                Re: Grading Trenches

                Backfill with sand being sure the trench is lower than necessary, then bridge at 5 foot intervals with mounds that are on the high side, prop pipes on the mounds and push down to pitch.

                Comment


                • #9
                  Re: Grading Trenches

                  Originally posted by DuckButter View Post
                  Backfill with sand being sure the trench is lower than necessary, then bridge at 5 foot intervals with mounds that are on the high side, prop pipes on the mounds and push down to pitch.
                  I would not recommend that. How do you compact under the pipe? That's fine in low impact areas, what about heavy traffic (parking lots)?
                  the dog

                  Comment


                  • #10
                    Re: Grading Trenches

                    Here we have to ensure our pipes are fully supported on a "firm bed"...
                    That pile and grade method would not fly in PHX...

                    Comment


                    • #11
                      Re: Grading Trenches

                      Tamp both sides.
                      I'm not talking about parking lots, for that matter it's outside my code to lay pipe more than 10' from the foundation.
                      Doing an underground below slab thats minimum 7" annular rock free backfill , then tamp it by foot then with tamps.
                      Once the plumbers job is done the GC finishes backfilling and tamps it mechanically.
                      Doing commercial undergrounds we did it this way, as on residential.
                      The pile/grade is just a way to get the pitch prior to filling & tamping.
                      Humorously wondering if you two thought I was saying ya just leave it that way and bury....

                      Comment


                      • #12
                        Re: Grading Trenches

                        It appears the way I left it, it looks like that was what I was saying.
                        NO I don't just pile pipes on mounds and leave 'em...wouldn't pass any inspections that way.

                        Comment


                        • #13
                          Re: Grading Trenches

                          Originally posted by DuckButter View Post
                          It appears the way I left it, it looks like that was what I was saying.
                          NO I don't just pile pipes on mounds and leave 'em...wouldn't pass any inspections that way.

                          Hey ducky, the pile and grade method wouldn't work out here either, so don't do it here either just teasing.

                          I dig, then compact, then use the spoil, if it is good enough, and sift the spoil back into the trench to shade the sewer, after inspection, I will sift another 12", compact and then backfill, compact etc to grade.
                          sigpic

                          Robert

                          Comment


                          • #14
                            Re: Grading Trenches

                            Originally posted by westcoastplumber View Post
                            Hey ducky, the pile and grade method wouldn't work out here either, so don't do it here either just teasing.
                            I'm actually going to recommend a new method to my state board based on my truncated description.
                            I'll call it the float and bury method, good when random pitches are required.

                            Comment


                            • #15
                              Re: Grading Trenches

                              Originally posted by DuckButter View Post
                              I'm actually going to recommend a new method to my state board based on my truncated description.
                              I'll call it the float and bury method, good when random pitches are required.

                              hahaha, everyone wants a roller coaster for a sewer fun ride to the city sewers
                              sigpic

                              Robert

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