On "Flush Valve" vs. "Cistern"

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When preparing sanitary ware for specifications and drawings, we often come across terms like "flush valve" and "cistern", which are different types of flushing systems for WC and urinals. Here's a general breakdown of their differences:

Flush Valves
  • Commonly used in non-residential projects, where there are higher volumes of water needed and more flushes per day
  • Does not require a small water tank for each WC/urinal that you see either hanging from the wall or as a part of the WC at the bank (Commonly where they hide guns and important objects in old movies)
  • Will not have a delayed flush after each flush, as water from sanitary pipes flow directly into the WC/urinal for flushing
  • Usually concealed in the wall behind the WC/urinal, and would require a space of 200-300mm; could be serviced from the top (where the pipe space behind it is not full height, and looks like a ledge where you can put stuff on) and from the back (if there is a corridor between two roles of WC/urinal that back face each other) which would require a space of 800mm to service (which is the more preferred design when there is enough space)
Cisterns
  • Commonly used in residential projects, where lower volumes and frequency is needed for toilet use
  • Requires that small water tank, which stores water from the main plumbing pipes that will be used for the next flush
  • Has a delay time for the cistern to fill up for the next flush
  • Could be exposed, or concealed; usually, the cistern is serviced from the front or top (if it has a ledge)

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