Best toilet flange size

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dayster

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Hi folks, I'm installing a new Toto Nexus toilet into a new floor. I haven't installed the toilet flange yet, or the drain piping. I was planning to use a 4" flange and 4" pipe, but I see that there are 4" flanges and reducing 4" to 3" flanges.

I presume that a 4" flange and 4" drain to the stack is better than 3", and that the reducing flange is a potential clog-enhancer. Am I right? Or is there some benefit to a smaller diameter flange and drain?

Thanks!
 
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Krow

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The 3" is used more for spacing issues.(like in between 2x8 joists) Thats almost all the time. One doesn't clog more than the other. Your toilet outlet is probably about 2 1/4" - 2 3/4" in diameter, so unless you are on heavy doses or morphine ( which hardens the stools before exiting your body), it probably would be considered an over-kill to go with 4"
 

hj

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flange

Regardless of the reasons why a 3" flange would work, I NEVER use anything other than a 3x4 closet bend with a 4" riser and a 4" flange over the outside of the pipe.
 

dayster

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Regardless of the reasons why a 3" flange would work, I NEVER use anything other than a 3x4 closet bend with a 4" riser and a 4" flange over the outside of the pipe.

Since the Nexus uses a PVC trap adapter, it was easy to see how the two different flanges matched up against the toilet's trap outlet. Turns out the reducing flange's hole doesn't line up well with the trap outlet, and would have created a potential clog-inducing lip.

I'm going 4" all the way to the stack - I've got the room for the pipe, so may as well go big.
 
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