General question on grading pipes.

[DIYluke]

I'm sure this is plumbing 101 for you experts but I'm no expert.
I've read that drains are supposed to be pitched 1/4" a foot up to 2.5", and pipes 3" and over are to be 1/8" per foot.
Everything I see in posts here and overhear on the construction sites (I'm not a plumber, but I am in the trades) just says 1/4" per foot regardless of size.

Which is it?

Thanks.

 

[Terry]

1/4" per foot unless you have permission from an inspector. I hear they will let 1/8" per inch on some 4" if it's really needed.

 

[Sponsor]

 

[DIYluke]

Thanks Terry.
This really is a great site.