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Old 10-12-2013, 10:21 PM   #1
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city sewage vent size

city main sewage vent line going thru the bathroom is a cast iron 6 inch pipe. we would like to move that vent line and make it smaller like a 3 inch line to be install in the wall vs outside of the wall in the bathroom. Can we change that line to smaller size and re-locate that vent line? we are remodeling the bathroom is the reason why I am asking. We live in MA.


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Old 10-13-2013, 07:55 AM   #2
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How many fixtures is it serving?
100% sure it's 6"?
Got a picture so we can see how far it sticks out?


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Old 10-13-2013, 02:44 PM   #3
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This would be the first house I've seen with a 6" vent.
It's probably 4". But typically you cannot downsize vents.
Best to call your authority having jurisdiction.
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Old 10-13-2013, 06:36 PM   #4
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agree with e plumber my guess 4" castiron ..and no you can not reduce a vent in size if you are doing a remodel get your permits and ask inspector to come out for a consoltation and get his opinion on what you are going to do ...ben sr
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Old 10-13-2013, 09:08 PM   #5
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Maybe hes looking at the o.d of the 4" cast and thinking its 6" coming through the roof.
Even a 4" vent all the way through up through a bathroom is awfully big unless youve got a lot of fixtures tied into it,around here an average vent is 2-3" and gets upsized to 4" 12" below the roof line to keep it from icing up in the winter.
"facts" have no relevance to this discusion
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