I am constructing a house not subject to code inspection in a remote rural area. There are 21 total fixture units serviced by two 2" vents extending through the roof. The vents are more than ample to service the fixtures. Although not required by the IRC, I just discovered that UPC requires that the total venting area be not less than the area of the building drain size. Thus a 4" building drain would require 12.57 sq. in. and a 3" drain 7.07 sq. in. However, my aggregate vent area totals 6.28 sq. in. As my vents are now set, it would be very difficult to enlarge my aggregate venting.
My building drain leads to a 4" sewer drain to a septic tank. Although I could run a 3" building drain, I would prefer to run a 4" drain. However, this would require another large vent under the UPC. Since the IRC is silent on aggregate venting, I am confused and wonder what problems, if any, would I incur by running a 4" drain with a 6.28" aggregate vent area? Would it be better to run a 3" main drain? Any suggestions or comments would be appreciated.
My building drain leads to a 4" sewer drain to a septic tank. Although I could run a 3" building drain, I would prefer to run a 4" drain. However, this would require another large vent under the UPC. Since the IRC is silent on aggregate venting, I am confused and wonder what problems, if any, would I incur by running a 4" drain with a 6.28" aggregate vent area? Would it be better to run a 3" main drain? Any suggestions or comments would be appreciated.