Re: 4" sewer main, can my vent stack be reduced to 3"?
Posted by Terry Love on February 28, 2004 at 14:13:58:
In response to Re: 4" sewer main, can my vent stack be reduced to 3"?

: I am in the middle of a remodel/addition. I ripped out all my cast/lead/galv pipe and am going all PVC. My main stack was 4" cast. I put a tyseal in and converted it to 4" PVC. Then in order to jog the pipes the way the short sections of cast were, I used two 22 degree 3" fittings...thus reducint my vent stack to 3". Is that illegal? I read somewhere if you have 4" sewer, you have to have a 4" vent stack. But I also read that a 3" vent will support something like 100 units? I will only have two baths and a kitchen. Rob,

Rob,
Most houses vent with a cross section of 3" depending on the local code.
Since plumbing is all over the home, you may have a 1.5" vent for the kitchen, and another one for the laundry. Count the number of vents going out the roof. This will give you some idea of what you have.




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