Toilet/sewer Pipe Size Venting - Plumbing - DIY Home Improvement | DIYChatroom

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Old 12-10-2011, 10:53 PM   #1
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toilet/sewer pipe size venting

Hi I am new here and I need some help on what size vent pipe I should run
for my toilet/ sewer pipe? The vent pipe will be dedicated just for the toilet. I live in Florida and I can not seem to find the right answers, I have seen and heard that I need to run a 3" vent pipe for a 4" sewer pipe and I
have heard that I need to run a 2" vent pipe for a 4" sewer pipe. Please help. Also can there be a clean out installed from the toilet drain? Does it matter where it is installed at? Like inline before the vent or after the vent. Above the vent or below the vent or does it need to be installed some where else. Can some one please help.


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Old 12-11-2011, 03:15 AM   #2
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I believe code states 2" vent for 3" or 4" toilet drain.
But the local AHJ has the last word.

You want the vent to come in immediately after the toilet flange
(or as soon as possible). A clean out can pretty much go anywhere you want or think you might need.


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Old 12-11-2011, 09:36 AM   #3
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As noted, you need to check with your local authorities. You may find you don't need to vent the toilet at all. Everybody talks about "the code" but in reality there are many more than one (counting versions), and the answer to your question depends on which one applies in your area. For me, it was the International Residential Code (IRC), 2003 version when I built my house. The IRC approaches venting much differently than the more common UPC - toilets do not require a vent.

That makes sense if you think about it. A vent's function is to put air behind the water in traps so they don't get sucked dry when a fixture is drained. Well, a toilet is nothing more than a very large trap, but one that you WANT to be sucked dry when you flush it.
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Old 12-11-2011, 10:19 AM   #4
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I would just call the local building inspector and ask him. You don't need to provide a lot of info, just ask what size vent you need.
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