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RJ539

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Loc'n: Rural Spokane County, WA

Is there any provision within the UPC venting requirements that would allow me to reduce the my 3" dia. soil stack down to a 2" dia. vent stack extending above the highest branch drain and then thru the roof, short of adding a second 2" dia. vent stack (for a total of (3) 2" dia. vents thru the roof) to adequately vent my 2-floor 3" dia. soil stack which drains into a 4" dia. septic line as it exits the building?

The soil stack will service 5 branch drains totaling 18 DFU's initially, with the possible future increase to 22 DFU if an island sink and dishwasher are added to the kitchen at a future date.

Possibly, the simpler question is, "Must a 3" dia. soil stack have a min. 3" dia. vent stack?"

Thanks in advance for any input, Russ
 

Jeff H Young

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I think it needs to equal the 4 inch sewer line not the 3inch but if you figure out the cross sectional area of 4 inch aproxx 12.56 inches 2 inch pipe 3.14 sq inch so you need 4 2 inch vents thru roof
 

Terry

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If you have three bathrooms in your home, you will need the equivalent of a 3" vent through the roof.
That can be two 2" vents and a 1.5" vent.
For four bathrooms, it would be four 2" vents.
Washington UPC
 

Jeff H Young

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yea thats right even though it has a 4 inch sewer it only requires 3 so 2 2 inch and 1 1 1/2 inch or a single 3 inch out the roof
 
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