Quote:
Originally Posted by peteinspain
standard plumbing falls are 1 in 40 for 4 inch drain (2.5%) and 1 in 60 for 6 inch but any fall for liquid is ok if its just water and time is not an issue
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There are three issues here, one issue is the physics of the plumbing solution, the second is the international code that applies to the plumbing solution and the third is the local code legality of the plumbing solution.
International plumbing code does not legally superseded all local plumbing code.
I know this to be true in the state where I live, Oregon, USA.
Here, although physics and International Plumbing Code would allow lower slopes, local code specifies slightly greater slope, and construction cannot legally proceed until a local inspector, who is bound by the local code, approves the particulars of the installation upon inspection.
I fully realize that DIY and legality may diverge, so it is wise to be aware of all aspects of the situation.
-AC_Hacker