# Vent Pipe Slope



## Mech

What is the minimum slope for vents under the 2009 IPC and the 2015 National Standard Plumbing Code? 
Is any positive slope adequate or must the vent pipe slope follow the slope for drainage pipe?

Thanks in advance.


2009 IPC Section 905.2 Grade
All vent and branch vent pipes shall be so graded and connected as to drain back to the drainage pipe by gravity.

2015 NSPC Section 12.6.1 Vent Slope
Vent and branch vent pipes shall be free from drops and sags and be sloped and connected as to drain by gravity to the drainage system.


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## Keystone

I would say positive slope would be any minimum or maximum slope so long as condensation, rain or other liquid could reasonably drain into the sanitary drainage system.


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## ICE

Me too.  Dead flat would still drain.


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## skipharper

Agree


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## north star

*@ ~ @*

Also, see *Section 911.3 [ `09 IPC ] - Slope and size of horizontal branch:*
"The maximum slope of the vent section of the horizontal branch drain
shall be one unit vertical in twelve units horizontal ( 8 per cent slope ).
The entire length of the vent section of the horizontal branch drain
shall be sized for the total drainage discharge to the branch."


*@ ~ @*


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## Keystone

I suspect the only reason to limit the slope of pipe would come down to fitment within the connecting joints/fittings.


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