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  1. #1
    Join Date
    Feb 2012
    Location
    Charlotte NC
    Posts
    20

    Default Toilet drain size?

    I need to move a toilet drain...Just discovered that the existing drain is about a 6" diameter PVC pipe. Does it need to be this large? Once another toilet, two sinks, and two showers tie into it, it still is 6". It seems to me the toilet would need to be only 3" until it ties into everything else. Is that right?

  2. #2
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,220

    Default Re: Toilet drain size?

    Are you sure it's 6"? I have never seen 6" pipe in any home. It could be 4". You can run two toilets on 3" pipe. But it should be increased to 4" once it exits the building.

    John

  3. #3
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    6,736

    Default Re: Toilet drain size?

    6" may be where your main line connects with the street city sewer. Most toilets have 3" drain, like john mentioned.

    Measure again.

  4. #4
    Join Date
    Feb 2012
    Location
    Charlotte NC
    Posts
    20

    Default Re: Toilet drain size?

    Ok...I measured, and the diameter is about 4.5"...So I'm guessing that's a 4" interior diameter. That still seems a little big for a toilet. I'd like to replace it with a 3", so would that be alright?

  5. #5
    Join Date
    Feb 2012
    Posts
    92

    Default Re: Toilet drain size?

    It should be alright but it would be better to stay at 4" less chance of clogs not that 3" is not big enough I would stick with what it is there may be reasoning for why the plumber did it in 4" due to fall or some other unknown reason we cannot see.

    Ben Franklin Plumbing Of Alpine
    304 Meadowlark Dr, Alpine, UT 84004
    (801) 960-1567 ‎
    http://www.benfranklinplumbingalpine.com

  6. #6
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,220

    Default Re: Toilet drain size?

    You can change the line to 3" but you can't reduce the line in the direction of flow.

    John

  7. #7
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    6,736

    Default Re: Toilet drain size?

    Before you rush to replace your 4" toilet drain with a 3" drain:

    1. What kind of floor is the toilet sitting on? concrete, raised foundation or second floor.
    2. Do you have an easy access to the drain?
    3. Why do you want to change it? do you have a leak?

  8. #8
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,969

    Default Re: Toilet drain size?

    I don't see any great advantage of reducing the size. The costs of the pipe and fittings is pretty much the same and the work is nearly identical.

  9. #9
    Join Date
    Feb 2012
    Location
    Charlotte NC
    Posts
    20

    Default Re: Toilet drain size?

    This might help to explain...my goal is to raise the 7 dropped-ceiling up to 8. The problem is that the pipes drop below joists b/c the the main drain need to run perpendicular towards back wall. I hope to re-route pipes towards window wall so they are parallel to joists. Then, I will drop them down at soffit (which will remain above cabinets, around perimeter of kitchen). When pipes are out of the way, I will raise ceiling up to normal 8 height.






  10. #10
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,969

    Default Re: Toilet drain size?

    In my fair city those 2" lines have to be introduced to the 4" line from the top with a Y fitting, you you wouldn't be able to raise that main drain unless you separated everything, which would mean a separate vent for each. More pics and less drywall please.

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