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How to backfill after laying waste lines under basement floor

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  • How to backfill after laying waste lines under basement floor

    I just dug a huge trench in my basement and laid waste lines for a new toilet, shower, etc. Some areas are over 2 feet deep.
    Before I re-pour the top four inches of concrete floor, what kind of fill should I use around and above the pipes?

    When I excavated I separated the materials, so should I backfill with...
    -the dirt
    -the dirt and small aggregate
    -the small crushed concrete (1/2" to 2")
    -the small and bigger chunked concrete (1" to 3")

    Or am I being anal retentive and it doesn't much matter?
    Just mix it all in and tamp?
    It's a small residential house with a low traffic basement bathroom.
    Thanks.

  • #2
    Re: How to backfill after laying waste lines under basement floor

    Originally posted by Dairylander View Post
    I just dug a huge trench in my basement and laid waste lines for a new toilet, shower, etc. Some areas are over 2 feet deep.
    Before I re-pour the top four inches of concrete floor, what kind of fill should I use around and above the pipes?

    When I excavated I separated the materials, so should I backfill with...
    -the dirt
    -the dirt and small aggregate
    -the small crushed concrete (1/2" to 2")
    -the small and bigger chunked concrete (1" to 3")

    Or am I being anal retentive and it doesn't much matter?
    Just mix it all in and tamp?
    It's a small residential house with a low traffic basement bathroom.
    Thanks.
    The first 12" should be clean dirt, free of aggregate. After that just be reasonable.

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

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

    Comment


    • #3
      Re: How to backfill after laying waste lines under basement floor

      Not even a little bit of sand

      Comment


      • #4
        Re: How to backfill after laying waste lines under basement floor

        Be sure to tamp it down if you use existing dirt, no need in having your new concrete floor cracking prematurely.
        I'd suggest using 2b stone to back fill though.

        Comment


        • #5
          Re: How to backfill after laying waste lines under basement floor

          Tell me if this is wrong; lay your pipe on compacted clean dirt, then lay 12" of sand on top. Then backfill as usual. Right or wrong?
          Buy cheap, buy twice.

          Comment


          • #6
            Re: How to backfill after laying waste lines under basement floor

            What? You guys are hauling dirt out to bring in 12" of sand? Is that a little overkill? I only bring in sand for waterpipe buriel.

            Comment


            • #7
              Re: How to backfill after laying waste lines under basement floor

              Originally posted by gear junkie View Post
              Tell me if this is wrong; lay your pipe on compacted clean dirt, then lay 12" of sand on top. Then backfill as usual. Right or wrong?

              While sand is nice neither the UPC or the IPC require sand.

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

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

              Comment


              • #8
                Re: How to backfill after laying waste lines under basement floor

                Originally posted by ToUtahNow View Post
                While sand is nice neither the UPC or the IPC require sand.

                Mark
                No, but they do not preclude its use either I believe.
                NSPC* (Not So Popular Code) § 2.6.3 says in part;

                "...backfill material shall be sand, gravel, or loose soil that is free of rocks and debris."



                * 2006 National Standard Plumbing Code, Section 2.6.3. The NSPC only applies in a handful of states.
                ---------------
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                Comment


                • #9
                  Re: How to backfill after laying waste lines under basement floor

                  Reason why I ask is that this is standard Navy practice. Sometimes we don't always do things the right way so I want to know if this is acceptable. Thinking out loud here; How do you achieve compaction rating with dirt placed right on pvc pipe? I know the first lift is 12" but is seems like the pipe could still be damaged when compacting. Since you can't compact sand, there would be at least 18" of soil between the pipe and the packer offering a little more protection.
                  Buy cheap, buy twice.

                  Comment


                  • #10
                    Re: How to backfill after laying waste lines under basement floor

                    There is a slight difference between the UPC and the IPC when it comes to backfilling. The UPC has you backfill 12" in multiple "layers" compacting as you go while the IPC has you backfilling 6" then compacting then another 6" then compacting again.

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

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

                    Comment


                    • #11
                      Re: How to backfill after laying waste lines under basement floor

                      So I can start chopping at my inspectors now for looking for a minimum of two inches of sand under my soil pipe and 6" on top.I never questioned them after all these years.I've spent 100's of dollars importing sand

                      Comment


                      • #12
                        Re: How to backfill after laying waste lines under basement floor

                        Originally posted by drtyhands View Post
                        So I can start chopping at my inspectors now for looking for a minimum of two inches of sand under my soil pipe and 6" on top.I never questioned them after all these years.I've spent 100's of dollars importing sand
                        You should always have a code book on your truck so you can ask the inspector to point out his reference when writing a correction. You would be surprised how many inspectors misuse the codes because they don't know them well enough.

                        As far as the OP's post, imagine digging all of the bathroom drains with 2' deep trenches in the basement. Unless it's a walkout basement you would have to carry all of that dirt out of the basement then carry all of the sand back down. The sand will give him a much better job but at what cost to his back?

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

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

                        Comment

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