Drain Hole Posted on 8th November 201525th July 2021 by ThePD (The Project Definition) Drain Hole is a hole or short conduit that allow excess liquid to drain away. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Engineering and tagged drain, process. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.