White toilet float valve example.

Flush Valve

Originally contributed by Jeff Butler • last updated 2/23/2021

If you’re like most people, you’ll probably use a flapper flush valve around 1800 times per year, exactly the same amount of times you’ll flush a toilet. Yet, there is a good chance you’ve never even heard of it. That’s because unless you’re repairing or replacing the working parts in your toilet tank, there’s little to no reason to ever think about it.

Definition

The flush valve on a toilet is typically a plastic or brass fixture that attaches to the outlet at the bottom of the tank. It is part of the flushing mechanism, which consists of a valve seat, a rubber or plastic flapper or ball, and an overflow tube; and is attached to the flush lever and toilet (flush) handle by a metal chain or lift wire. The flapper (or ball) covers the outlet and sits tightly against the seat. The flapper is held in place by water pressure when the tank is full and is lifted to empty the water from the tank when the toilet handle is pressed. As the water empties, the flush valve returns to its closed position, allowing the tank to refill with water.

What Can Go Wrong With A Flush Valve?

For the most part, a flush valve is not that mechanically difficult and there are only a couple of things to look for when there is a problem. On a positive note, they are relatively inexpensive and easy to replace, making it a great DIY task for any homeowner:

  • Most commonly, the flapper is not seating properly against the flush valve seat, allowing the water in the tank to drain into the bowl, activating the fill valve to maintain the designated water level.
  • Additionally, the chain or lift wire that attaches the handle and flush lever to the flapper may be either too long or too short. If it is too long, the flapper may close before the toilet completely flushes with a single press of the handle; or, the chain may get stuck between the flapper and the seat, causing the toilet to continue to run. If it is too short, the flapper may not close completely, leaving the outlet exposed.
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