outflow vs seepage

outflow

noun
  • Something that flows out of a sewage treatment plant. 

  • Any outward movement. 

  • The process of flowing out. 

  • A fluid that flows out. 

  • A stream of gaseous material emanating from an active galactic nucleus. 

  • The part of a system that allows material to flow out. 

verb
  • To flow outward. 

seepage

noun
  • Water that has seeped or oozed through a porous soil. 

  • The process by which something, especially a liquid, leaks through a porous substance; the process of seeping. (Also used figuratively: the process of diffusing.) 

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