Steam was first used as a motive source to drive pumps, locomotives during the Industrial Revolution in the 18^th century.  Later on, steam was used as heating source. Removing condensate by manually operating a valve was a problem, for it leaks steam. So the steam trap, a valve that can automatically remove condensate, was invented.

When steam gives up latent heat, steam condenses, producing condensate. Condensate must be removed so that heating efficiency is not affected. Steam traps are needed to filter out condensate and non-condensable gases (such as air) without losing steam. The steam is used for heating or as a driving force for mechanical power, so steam traps are important because they prevent steam from being wasted.