By the way Mwarney...

Plumbing codes in the USA mandate that pipes 3" and smaller get 1/4" pitch per foot minimum.

Pipes 4" and larger can have a minimum 1/8" pitch per foot.

If not on commercial job using a transit level to keep track of slope I take a 4 foot level and I tape a 1/2" block of wood at the very end of the level which is equal to 1/8" pitch per foot so that when I place the level on the 4" or 6" underground pipe, for example, and get a level reading from the level I know I have a properly pitched pipe for sure!

Good luck!

MARK