hydrant vs water pipe

hydrant

noun
  • An outlet from a liquid/fluid main often consisting of an upright pipe with a valve attached from which fluid (e.g. water or fuel) can be tapped. 

water pipe

noun
  • A pipe that is a conduit for water; an essential element of plumbing. 

  • A device for smoking, such as a hookah or bong, in which the smoke is drawn through a container of water before inhaling. 

How often have the words hydrant and water pipe occurred in a corpus of books? (source: Google Ngram Viewer )