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Thread: Toilet flange above or level with floor

  1. #1
    DIY Junior Member dmaceld's Avatar
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    Default Toilet flange above or level with floor

    I find several comments in this forum where the authors say a toilet flange should be on top of the finished floor. There are also a couple of posts where in that case the poster had problems with rocking toilets due to insufficient space between the flange and toilet bottom. I have a copy of Code Check Complete which is a summary of four primary building codes. In there the authors have an illustration specifically showing the flange top level with the finished floor as being the correct installation and a big NO circle over the illustrations showing the flange on top of the finished floor and below the finished floor.

    What I find of the plumbing codes the only code requirement is for the flange to securely fastened to surface below it.

    Soooooo, what is the correct positioning of the flange to avoid clearance problems and still have a water tight seal?
    Last edited by dmaceld; 01-07-2009 at 07:36 PM.

  2. #2
    Illinois Licensed Plumber SewerRatz's Avatar
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    Only part in Illinois plumbing code is as follows.

    Section 890.360 Water Closet and Pedestal Urinal

    Fixture connections between drainage pipes and water closets, floor outlet service sinks and pedestal urinals, and earthenware trap standards shall be made by means of brass, copper, hard lead, plastic, or iron flanges; caulked, soldered, screwed or solvent welded to the drainage pipe. Flanges of hard lead, plastic and iron flanges for no-hub or compression joints shall be secured to the floor. The connection shall be bolted, with a gasket, washer or setting compound, between the earthenware and the flange. The floor flange shall be set on an approved firm base. The use of putty or non-drying plumber's putty manufactured specifically for plumbing installation is acceptable

    It does say it needs to be set on an approved firm base. I always put it on the sub-floor, and let the tile guys tile around it. So I make sure it will be installed flush with the finished floor.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    There are two issues...the flange must be firmly attached, and, it is designed to sit OVER the finished floor and anchor through it. If the flange is installed tight to the floor surface AND that surface is flat and level AND the flange is not poorly designed AND the toilet is standard with decent quality control, you should be able to use a standard wax ring and get a reliable, waterproof, gasproof seal. A thick wax ring filling a wide space isn't as reliable (but could last a very long time if not disturbed) as a thinner one. Since a typical flange ring is only in the order of approximately 1/4" or so, if it was ultimately level with the finished floor, would having the wax an extra 1/4" be a major factor? Maybe if you got really aggressive with a plunger, but probably not.

    Issues with a toilet not fitting are usually related to a flange that is not sitting ON the finished floor and is sitting above it, or not level with the floor. Also, some people think the use of a horn embedded in the wax ring is a good idea...the higher the flange is, especially on a 3" drain pipe, the more problems you'll have since that horn does have some uncompressable thickness and width and may not fit into the throat of the flange.

    Essentially, any properly made toilet should fit on any code approved flange IF the flange is installed on TOP of the finished floor properly. There are a lot of junk toilets out there that may not meet industry standards.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Plunger/TurdPuncher kingsotall's Avatar
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    Quote Originally Posted by SewerRatz View Post
    I always put it on the sub-floor, and let the tile guys tile around it. So I make sure it will be installed flush with the finished floor.
    OK, here goes...
    WE SET THE FLANGE FLUSH WITH THE FLOOR TOO!

  5. #5
    Plumber Cass's Avatar
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    Always on the finished floor for proper tolerances between toilet and flange so the wax ring can do it's job to the best of its ability.

  6. #6
    Illinois Licensed Plumber SewerRatz's Avatar
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    Quote Originally Posted by Cass View Post
    Always on the finished floor for proper tolerances between toilet and flange so the wax ring can do it's job to the best of its ability.
    I do not use wax, I use the Zurn Neo seal or plumbers putty.

  7. #7
    Plumber McMike's Avatar
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    the last company i worked for(service plumbing and remodels) had a policy of flange on finished floor, the majority of the leaky toilet floor seals we were called to repair were 3inch pvc flange 10-15 years old, below floor level, if we used thicker wax we would still have problems within our 2 year warranty, so the company requires flange to be cut out and repiped to sit on FF, those flanges that were reset on FF would easily last well past our 2 year warranty, it was very rare to see a leaky floor seal with a flange set on FF

  8. #8

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    Now you have me worried...! I'm just in the process of installing a couple of Aquia lll. I have the old toilet removed and the flange cleaned up and ready to install.
    Came back here to double check everything before dragging out the drill, and I see these comments on the flange being flush with the FF.
    My flange is flush with the concrete floor, and the thickness of the tile below FF, maybe a quarter of an inch, but solidly mounted.
    The old wax ring came off easily in one piece. It is about an inch and a quarter thick in it's compressed state. I'm guessing the existing wax rings must be the thicker ones.
    The house is five or six years old and never had a leakage problem.
    I'm heading for HD now to buy a couple of new wax rings and new water inlet pipes and some carbide drills..
    I sure don't want to tear up my floor to raise the flange a quarter inch, so I'm going with the thicker ring and hoping all will work out, since it has worked for five years with the flange lower than FF.
    The old closet bolts mounted in the flange are solid and appear to be like new. Is there any reason to replace them..?
    Hopefully my wife will still be talking to me by the end of the day......??

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    The wax must compress when you set the toilet...you need enough thickness to have that happen. There are flange extenders you can use rather than replace a flange.

    Because of the way the toilet is designed, it might not leak unless there is an obstruction and the drain backs up. It could leak sewer gasses, though. Depends on your system whether you'd notice.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10

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    Thanks, Jim. I'm getting smarter by the minute. Fortunately HD is only a couple of blocks away.
    I mentioned my old seal was an inch and a quarter. On closer inspection, it's two put together....!
    I'm on the way back to HD to exchange a few parts, so I will check out a flange extention.
    The good news is, the second toilet should be a breeze. This one has taken much longer than expected, but I prefer to go slowly and not screw anything up. If I had to depend on my plumbing abilities to put food on the table, I'd have starved to death long ago....
    Good thing we have four bathrooms, or I might have to buy some rubber bands...! Looks like tomorrow before this one is working....

  11. #11
    Plumber krow's Avatar
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    In the older days, when lead bends , and eventually copper drains were introduced, the codes expected you to affix the floor flange on top of the finished floor. The thickness of the flange played a big part in that thought process. It would allow all tolerances.

    When plastic came into play (PVC and ABS) you will notice that the flange is slightly thicker. To compansate, they amended any codes to allow for the difference in thickness. We, in Canada, place our platic flanges flush with the finished surface (level with the tile floor) and or 1/8" higher than the finished surface. This would allow you to use a sponge gasket if you wanted to. (in both cases, always fastening the flange to the floor or subfloor)

    Placing the PVC OR ABS flange on top of you finished surface, you are almost obligated to use a wax gasket, whether you like them or not. The wax will squeeze much further than your sponge gaskets and the flanges do not need to be exactly level. The wax will form to its new level, or lack of level

  12. #12
    In the Trades Gary Swart's Avatar
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    I have always understood the flange was to be set on top of the finished floor and will continue to do that on any flanges I install in the future. However, if I am asked to install a toilet and find a perfectly good flange installed flush with the floor, I will not hesitate to install the toilet. Now recessed another 1/4" is another matter, but that's for another thread.

  13. #13

    Default Success...

    Thanks to all for the good tips. One is installed with one to go. It turned out to be a slam dunk. With the exception of drilling four holes through tile and concrete, it was much easier to install than a standard toilet..!
    Everything went smoothly, and it works perfectly with no leaks. I spent more time worrying and studying than installing. The next one will go quickly...
    The flange being 1/4" below FF was simple to resolve. Fluidmaster makes a thicker wax ring, which handled the problem easily.
    One benefit of having the socket adaptor is, you put it in place w/o the seal, and you can see and feel how much gap you have to deal with, and after it's installed with the wax ring, you can see and feel the results, so there is no guessing.
    So far we love it, and I'm very happy I took Terry's advice and spent the extra hundred for the ADA....

  14. #14
    DIY Junior Member dmaceld's Avatar
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    Quote Originally Posted by krow View Post
    In the older days, when lead bends , and eventually copper drains were introduced, the codes expected you to affix the floor flange on top of the finished floor. The thickness of the flange played a big part in that thought process. It would allow all tolerances.

    When plastic came into play (PVC and ABS) you will notice that the flange is slightly thicker. To compansate, they amended any codes to allow for the difference in thickness. We, in Canada, place our platic flanges flush with the finished surface (level with the tile floor) and or 1/8" higher than the finished surface. This would allow you to use a sponge gasket if you wanted to. (in both cases, always fastening the flange to the floor or subfloor)

    Placing the PVC OR ABS flange on top of you finished surface, you are almost obligated to use a wax gasket, whether you like them or not. The wax will squeeze much further than your sponge gaskets and the flanges do not need to be exactly level. The wax will form to its new level, or lack of level
    Well, it's been a few months and the bathrooms are done, along with all the house, and we are moved in! My experience with the toilet installations was pretty much dead on with the response above. I put the ABS flanges on top of, and tight to, the finished floor. I installed Toto Drake ADA elongated toilets, a favorite of this forum's followers. It turns out there isn't enough depth around the outlet to allow the use of some no-wax seals. The flange on the Fluidmaster seal I had was too thick and the toilet missed touching the floor by about 1/8". I used a no-wax seal I got from a plumbing supply house, don't recall the brand, that barely fit. In fact there still is a slight gap but the toilet doesn't rock. If I ever install another toilet I believe I will go flush, or maybe 1/8" above the finished floor. That should allow the use on any good seal, wax or no-wax.

  15. #15
    Moderator & Master Plumber hj's Avatar
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    Default flange

    quote; I have a copy of Code Check Complete which is a summary of four primary building codes. In there the authors have an illustration specifically showing the flange top level with the finished floor as being the correct installation and a big NO circle over the illustrations showing the flange on top of the finished floor and below the finished floor.

    I always install it on top of the floor. If you have a toilet with a deep recess and the flange is flush with the floor, a conventional wax ring will not have any compression. The only way a flange on top of the floor COULD cause a wiggling problem would be if the toilet has a very shallow recess, and only the most mediocre toilets would have that, AND the flange is a plastic one with a very thick flange. Normally, the ONLY way to be sure the toilet is sealing properly is to have the flange on top of the floor.

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