Flush Valve

Definition - What does Flush Valve mean?

A flush valve is a self-closing valve designed to release a large volume of water when activated. This mechanism is often used to flush a toilet or urinal.

The valve and associated hardware are located within the toilet tank or in the body of the urinal. Most toilets have a lever or push-button activator to operate the flush valve.

Worn flush valves cause toilets to leak water, creating noise and waste. Corrosion erodes flush valves over time, opening the seal between the tank and toilet bowl, allowing water to escape from the tank continuously.

Corrosionpedia explains Flush Valve

The flush valve provides a means to open the water supply line to a fixture, permitting a preset volume of water to pass through it to cleanse the fixture with each flush.

The principle parts of a flush valve are:

  • Trip lever (handle)
  • Lift rod or chain connecting trip lever to tank-ball or flapper
  • Tank-ball or flapper (stopper)
  • Flush valve seat (hole in bottom of tank)
  • Overflow pipe (vertical pipe in center of tank)

Flush valve leaks are caused by:

  • Worn out or defective tank-ball, flapper, seal or disk
  • Damaged flush valve seat
  • Split or hole in the overflow pipe
  • Damaged gasket under the flush valve
  • Wrong type of flapper being used
  • Chain or strap is too long and gets stuck under the flapper or ball
  • Piece of foreign material stuck under the flapper or ball
  • Flush valve seat corrosion or chipping, causing the flapper to not seal correctly

Many modern commercial toilets use a flushometer instead of a standard flush valve. Because flush valves rely on pressure and flow, they can reset faster than gravity tanks.

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