Folks, don’t let this happen to you.
A few weeks ago I stopped by a brewery in a nearby town for lunch. It turned out they were closed. Construction crews were inside tearing out the concrete slab, replacing the ductile iron drain piping in the brewery. You can see how badly corroded it is! This type of corrosion happens in the upper part of the pipe, hydrogen sulfide gas in the pipe creates a weak sulfuric acid, which slowly and continually eats away at the iron. Do not install ductile iron for brewery wastewater applications!
Stainless steel is always the best wastewater pipe option for a brewery, but as we all know, most brewers can’t afford stainless- especially for a below grade out of sight application. Next best options are ABS, PVC, and PE. You can see above how the plastic fitting is not corroded at all. The drawback to plastics is temperature, they can melt and collapse if boiling water is spilled down the drain. That would never be the plan, but mistakes happen.