plumbing vs water pipe

plumbing

noun
  • The pipes, together with the joints, tanks, stopcocks, taps, and other fixtures of a water, gas, or sewage system in a house or other building. 

  • A system of vessels or ducts in the human body, especially the genitourinary system. 

  • The trade or occupation of a plumber. 

  • Practical, concrete work serving to support other work. 

  • A Murasugi sum where each disk summed along has its boundary subdivided into four segments. 

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 plumbing and water pipe occurred in a corpus of books? (source: Google Ngram Viewer )