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Old 03-06-2010, 01:20 PM   #1
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Vent pipe size for toilet

Hi, I'm installing an all new DWV system in a remodel. An inspector said that a 3" drain on a toilet requires a dedicated 3" vent. If I have a dedicated vent, doesn't the size seem excessive? I had in my memory that the vent for a dedicated water closet drain needs only be 1 1/2"


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Old 03-06-2010, 10:55 PM   #2
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Vent pipe size for toilet

Inspector is a little off. If you are venting just a water closet a 1 1/2" should be fine. But I normally run 2" just because it will be easier to snake from the roof and less 1 1/2 to carry.

Have the inspector show you in code where a 1 1/2 vent can't be used for only 1.5 dfu's


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Old 03-07-2010, 10:58 AM   #3
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Vent pipe size for toilet

what he said! id use a 2" also for maintenance reasons but 1 1/2" would be legal in my book,just make sure it increases to 4" a foot before daylighting through the roof
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Old 03-07-2010, 12:46 PM   #4
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Vent pipe size for toilet

2" is code minimum in Oregon.
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Old 03-09-2010, 02:21 PM   #5
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Vent pipe size for toilet

How far is the toilet from the main stack? You might not need a separate vent at all.
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drain , dwv , toilet , vent

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