Before revision: In plumbing, a Fixture Unit (FU) is ' a unit of measure, based on the rate of discharge, time of operation and frequency of use of a fixture, that expresses the hydraulic load imposed by that fixture on the sanitary plumbing installation .'
After revision: In plumbing, a Fixture Unit (FU) or Drain Fixture Unit (DFU) is " a unit of measure, based on the rate of discharge, time of operation and frequency of use of a fixture, that expresses the hydraulic load imposed by that fixture on the sanitary plumbing installation .'