2 Gravity Flow of Liquids in Pipes

My favorite method for designing gravitational flow of Newtonian liquids in mechanical and civil piping systems is covered here. It is very good for designing steam condensate return systems, gravity-flow portions of cooling tower water systems, and industrial process drain systems (but not sanitary waste drains, which are designed to local building codes.)

It is quick, a widely accepted old standard, easy to understand, and accurate enough for any purposes I've encountered so far. It combines a simple equation with a couple of normalized graphs, which are included.

If you will adopt my design philosophy for gravity flow piping, and ensure your design is followed and its intent is realized in the constructed system, your gravity systems will work as planned every time.