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Thread: Measuring For A New Toilet

  1. #1
    DIY Junior Member Noddaplumber's Avatar
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    Nov 2008
    Watauga, Texas

    Default Measuring For A New Toilet

    I am purchasing a new toilet for my master bath this week. The plumbing supply said to measure from the wall to the hold down bolts. That measures 13 inches. So, I assume I can use a 10 or 12 inch toilet and live with extra space between tank and wall on a 10 inch.

    Going back to an old post and problem. My front bath has had no toilet for months. The plumbers tell me to measure from the wall to the center of the flange which is 9 inches. Thus, they say I need to rip up my flooring to extend the flange. But when I measure from the wall to the hold down bolts I hit 10 inches. The distance between the hold down bolts in the front bath is 6 inches.

    So, who is right? The plumber or the plumbing supply house? How do I tell what size toilet I need? Are the plumbers trying to scrounge up money on the front bath by saying I need to rip up the floor? Would a 10 inch toilet work after all?


    Last edited by Terry; 04-13-2009 at 09:20 AM.

  2. #2
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    You will want to use a 12" toilet on the new bath. There will still be some space between the tank and wall. The other toilet problem is not quite as simple. It seems that there is no exact industry standard on rough-in sizing. For example, some toilets listed as 12" actually only take about 11-1/2". So, it may depend on what toilet listed as a 10" you try to fit on your flange. My guess is that if you do find one that will fit, it will be a tight fit. Compounding your problem is the fact that there are not many 10" toilets to choose from. If you don't get a more precise answer, you might send Terry a PM. He should be able to give you the data you need.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    When properly installed, the two bolt holes that hold them in place to mount the toilet are parallel with the wall (i.e., equidistant from the wall and centered around the flange). Note when measuring, do not include the baseboard unless it is very high...measure from the actual wall or from the baseboard then add the thickness of the baseboard for the actual measurement.

    When you install a toilet, there is a small amount of wiggle room in the bolt slots to shift the toilet a little. Keep in mind that this also means the toilet outlet won't be centered on the drain pipe, so you must not move things too much. A 1/4" is fairly easy, more could be a problem.

    Some of the Toto toilets that come in 10" rough, normally have about 3/4" behind then. So if you had 9-1/4", it would fit, but the tank would be touching the wall.

    You really need to recheck things to figure out what you have. By limiting yourself to a few 10" toilets (and there aren't all that many), you really limit your choices of toilets. If you could move it to become a 12" rough-in, your options open up radically.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    Rough in is the distance from the finished wall to the center of the drain.

    Normally the bolts are at center.

    Most toilets have 3/4" behind the tank,
    So 12" toilets will work at 11-1/4"
    The 12" Drake works at 10-7/8"
    A 10" toilet will work at 9-1/4"

    Last edited by Reader Review; 01-06-2009 at 10:36 AM.


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