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  • Building Drains

    According to the 2006 IPC, If my total DFU's is 42 I should use a 3 inch building and sewer drain pitched a 1/4 per foot. I have three toilets in this setup. I was told to increase to 4 inches whenever I go over two toilets. What is the correct answer and why? Thanks. Is this written anywhere or is this just a rule of thumb.

  • #2
    Re: Building Drains

    Originally posted by laz001 View Post
    According to the 2006 IPC, If my total DFU's is 42 I should use a 3 inch building and sewer drain pitched a 1/4 per foot. I have three toilets in this setup. I was told to increase to 4 inches whenever I go over two toilets. What is the correct answer and why? Thanks. Is this written anywhere or is this just a rule of thumb.
    I'm assuming that by building and sewer drain, you are referring to the underground lateral drain to the city main (or the underground building sewer to the septic).

    If so, I'm not sure what the local code is in Alabama, but in Illinois, only 4" is allowed underground.

    -Chris

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    • #3
      Re: Building Drains

      Originally posted by laz001 View Post
      According to the 2006 IPC, If my total DFU's is 42 I should use a 3 inch building and sewer drain pitched a 1/4 per foot. I have three toilets in this setup. I was told to increase to 4 inches whenever I go over two toilets. What is the correct answer and why? Thanks. Is this written anywhere or is this just a rule of thumb.
      Who was it that told you that?

      Here is your Code

      http://www.archive.org/details/gov.al.plumbing

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

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

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      • #4
        Re: Building Drains

        Originally posted by ToUtahNow View Post
        Who was it that told you that?

        Here is your Code

        http://www.archive.org/details/gov.al.plumbing

        Mark
        Thanks for the information. I have 2006 IPC which is what Alabama uses. Correct me if I'm wrong according to Table 710.1(1), if I have 42 DFU's (three toilets in this calculation) the minimum size of my building drain should be 3 inches.

        P.S. The reference material that I used was an Audel Wiley book. Stated that in some jurisdictions (did not specify) number of DFU's on a 3" building drain was a lower. Again IPC 2006 states that max number is 42 DFU's on 3" building drain, 1/4" pitch. So I would say that I am correct if I use 3" building drain.

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        • #5
          Re: Building Drains

          for a few cents more, 4" will give the home a chance to expand Easier. What's the big deal
          about going 3" instead of 4"
          I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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          • #6
            Re: Building Drains

            Originally posted by toolaholic View Post
            for a few cents more, 4" will give the home a chance to expand Easier. What's the big deal
            about going 3" instead of 4"
            I was thinking the same thing, put in 4" and your safe. Does he realize 4" will handle 5 times as much fixture units as 3".
            They allow 2" underground here in Mich. When the housing boom was happening, none of those production plumbers or builders cared about future expansions,{or the homeowner was too cheap in alot of cases too}, so if they had a kitchen sink, or laundry tub, on one side of the house, all they did was run 2" underground. So if you want to add a basement bathroom,I tell them to get out the check book. Oh, and to rough the underground in before the floor was poured, that was way too expensive at the time, the $5000.00 front entrance door, was alot more important.

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            • #7
              Re: Building Drains

              I understand expansion and all that. There is no big deal about staying at 3" or going to 4". Personally I would go 4". All I want to know is if I have 42 DFU's according to the IPC I can use 3". Just looking for a simple yes or no. Thanks. I want to know the minimum I can go with the 42 DFU's.

              For example: The code book says that the minimum a toilet can be from a side wall is 15" from finished wall. If I asked someone what the minimum was they would say 15" from finished wall. That doesn't mean I can't go to 19". Not that I would.

              Also, someone said 2". You can't go 2" if you have a toilet. Your drain would be decreasing in size.

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              • #8
                Re: Building Drains

                Okay. The 2" was a setup with no toilet. But that didn't answer my original question. I have toilets.

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                • #9
                  Re: Building Drains

                  Originally posted by laz001 View Post
                  I understand expansion and all that. There is no big deal about staying at 3" or going to 4". Personally I would go 4". All I want to know is if I have 42 DFU's according to the IPC I can use 3". Just looking for a simple yes or no. Thanks. I want to know the minimum I can go with the 42 DFU's.

                  For example: The code book says that the minimum a toilet can be from a side wall is 15" from finished wall. If I asked someone what the minimum was they would say 15" from finished wall. That doesn't mean I can't go to 19". Not that I would.

                  Also, someone said 2". You can't go 2" if you have a toilet. Your drain would be decreasing in size.
                  Just for the record, I didn't suggest 2" for your application, was just ranting,I guess, about 2" being allowed underground here in Mich.
                  I know what your saying about wanting to know, theoretically if 3" is adequate. One of these code book junkies will be able to tell you soon. Sorry I don't have the time to look it upfor you right now.

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                  • #10
                    Re: Building Drains

                    Originally posted by laz001 View Post
                    Okay. The 2" was a setup with no toilet. But that didn't answer my original question. I have toilets.
                    Toilets are overrated. Give Me a tree anyday
                    I can build anything You want , if you draw a picture of it , on the back of a big enough check .

                    Comment


                    • #11
                      Re: Building Drains

                      Originally posted by laz001 View Post
                      Thanks for the information. I have 2006 IPC which is what Alabama uses. Correct me if I'm wrong according to Table 710.1(1), if I have 42 DFU's (three toilets in this calculation) the minimum size of my building drain should be 3 inches.

                      P.S. The reference material that I used was an Audel Wiley book. Stated that in some jurisdictions (did not specify) number of DFU's on a 3" building drain was a lower. Again IPC 2006 states that max number is 42 DFU's on 3" building drain, 1/4" pitch. So I would say that I am correct if I use 3" building drain.
                      I am in UPC and your statement would be correct here on a vertical pipe. 4 water closets is the jump to 4" line as a rule. But remember it states the max amount of units so going larger pipe would be better but I know sometimes the room is not there on a remodel.
                      Seattle Drain Service

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                      • #12
                        Re: Building Drains

                        The southern building code that we use requires a jump to four inch when there are more than two water closets on the horizontal building drain. I would have to get the code book out to explain why.

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                        • #13
                          Re: Building Drains

                          I'm to lazy to get the code book out too, but if I had to guess, I would say about 36 DfU's on a 3" main drain, or bldg drain, and like every one said there use to be limit of 2 water closets, but WTF, at 1.6 GPF now they should allow 4 or 5.

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