Maximum distance between water closet and vent

[Mikepawlik]

Using the 2018 IPC code, can anyone tell me the maximum distance from the water closet to the vent. In the code it says:

"Exception: The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited."

The way I would like to put in a toilet, the vent would be about 12 feet from the water closet to the vent. I see folks posting that the maximum distance is 6 feet. I read the code as this beng acceptabe.

Where am I going wrong?
Any help is appreciated!

 

[Kreemoweet]

Different plumbing codes (and there are several in use in the U.S.) have different requirements.
Sometimes VERY different requirements. If your local jurisdiction uses the 2018 IPC, then I
suppose you are good. If not, then what it says in the 2018 IPC is irrelevant.

 

[Sponsor]

 

[Tuttles Revenge]

I don't plumb under IPC, but I believe your reading of the code is correct. It further is made clear in 909.2 which would limit trap arm distances to the diameter of the fixture drain. Same exception made for water closets.

The reason this exception is made, is because toilets require a siphon to fully clear the bowl and then rely on the tank to refill the bowl to prevent sewer gases from entering the structure. A vent on the toilet trap arm really exists to allow air to move out of the way for the displacement of the water.

 

[wwhitney]

Note that the vent still needs to be located at or before the WC drain joins another drain. So under the IPC the 12' is fine from WC to vent as long as that 12' drains only the WC, nothing else.

Cheers, Wayne