What Is A Toilet Flush Valve?

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Last Updated on September 6, 2022 by acechapman

A toilet flush valve is located at the bottom of the tank. It allows water to flow from the tank to flush the bowl. The majority of toilets have a flush valve that is 2 inches in diameter, but some high-performance toilets have a flush valve that is 3 or 4 inches.

The flush valves are connected to the toilet tanks using a locknut that is located underneath the tank. The flush valve is then covered with a toilet tank to bowl gasket, also known as a “spud washer”, at the bottom.

The toilet tank-to-bowl gasket seals the tank and bowl together. If your toilet is leaking from the tank to the bowl after flushing, then the gasket may not be sealing properly.

The toilet flapper is placed on top of the opening for the flush valve to create a watertight seal. This seal allows the toilet tank always to be full and ready to use.

There are 2 pegs on the flush valve where the flapper ears of your toilet can be hooked. This provides a means of securing the flapper.


Understanding the entire toilet’s workings is important in order to understand the flush valve. Two mechanisms make up a toilet: the flushing mechanism as well as the refill mechanism.

The flushing mechanism includes the toilet handle, toilet handle arms, lift chain, and toilet flapper.

The refill mechanism starts with the fill valve, then the toilet tank, the refill tube, and the overflow tube.

  • Push the toilet handle down and the lift chain, which was at that time slack, and a handle arm pulls up.
  • The lift chain lifts off the toilet flapper and closes after.
  • The flush valve allows water to flow from the tank into the bowl.
  • The toilet releases the handle to relax the lift chain. The flapper will fall back and seal the flush valve.
  • The fill valve refills the toilet tank.
  • The fill valve fills up the tank and the refill tube sends water to the bowl via the overflow tube, which is connected to the flush valve.

The large tube located in the middle of the tank is called the overflow tube. It connects to the flush valve. The refill tube can be clipped to the top of an overflow tube. It releases water into the bowl, which acts as a barrier to sewer gases.

The overflow tube channels excess water to the bowl if the fill valve fails and fills the tank constantly. The tank water level should not be more than 1/2 inch below the tube.

what is a toilet flush valve


Flush valve sizes didn’t matter much before low-flow toilets were introduced. Nearly all toilets used a 2-inch standard flush valve. Toilets back then used 3.5 gallons per flush, so even a small toilet valve would still work well.

Low-flow toilets require 1.6 gallons or less water per flush. A 1.6 GPF toilet will still flush with a 2-inch flush valve. However, engineers at toilet manufacturers had to find a way to make a flushing toilet that uses less water and is as powerful as possible.

This is how the 3-inch and 4-inch flush valves were created. How you get the water to your bowl is key to a strong flush.

You can have a powerful flush if you pour the water into the bowl quickly. The 4-inch flush valve is found in toilets like the American Standard Champion 4. It is therefore one of the most powerful flushing toilets.

You will need to purchase the exact size flush valve replacement or you could end up with a non-functional valve.

Original replacements from the manufacturer of your toilet tank are the best options for flush valves. To order a flush valve, get your toilet model number stamped on your tank.

Fluidmaster also offers great universal flush valves.


Most likely, you will use 4 types of flush valves.

  1. Standard Flush Valves 
  2. Canister Flush Valves
  3. Flushometers
  4. Dual-flush Valves


These are the most popular types of flush valves. These flush valves are compatible with single-flush toilets and have a flapper seal.

A standard flush valve can be used to allow the toilet tank to use either a float ball or float cup. It takes up very little space in the toilet tank.

This flush valve is much cheaper to replace. This flush valve is also easier to clean if there are any mineral deposits or debris that might be preventing the flapper seal from sealing properly.


The canister flush valves are located in the middle section of the toilet tank. These canister flush valves are used in particular by Kohler toilets such as the Kohler Cimarron.

The cylindrical canister valve has a rubber seal/gasket at its bottom and is attached to a chain that is connected to the flushing handle. The toilet handle is pushed down so that the chain lifts the canister, allowing water to flow into the bowl.

A canister flush valve, unlike a standard flush valve that hinges to one side of the flapper, lifts completely and allows water to flow to the bowl at a 360-degree angle.

This design allows water to flow to the bowl more quickly, resulting in powerful flushes.


Flushometers are commercial flush valves. It can be used with tankless toilets. Tankless toilets, as the name implies, are toilets that have no tanks and do not flush automatically.

Canister flush valves have enough water pressure to flush the toilet and are therefore not required to have a tank. A tank is necessary because most water sources in buildings are not strong enough to flush a toilet.

You will find flushometers in public toilets and urinals. Each push of the button releases a measured amount of water.


Dual flush toilets have dual flush valves. Dual flush toilets allow the user to choose whether they want to flush liquids with less water or more.

Flush buttons are almost always used in dual flush toilets. These buttons can be found at the top of your tank lid. Dual flush valves are located in the middle of the toilet tank, just like canister flush valves.

The dual flush valve seal opens when you press any button. Water will flow to the bowl by allowing it to lift off.

what is a toilet flush valve


  1. Toilet running continuously – Usually, a toilet running constantly is due to a defective flapper. But sometimes it’s due to a cracked flush valve.
  2. Leakage of the toilet between the bowl and the tank – This is an indication that either the flush valve has cracked or the gasket connecting the bowl to the tank is leaking. A wobbly toilet tank could also cause it.

Common Types Of Valve Damage

If the toilet flush valve is not replaced promptly, it can cause serious problems. Toilets that leak large quantities of water can be caused by worn flush valves, depending on their condition. If you leave it unfixed, you could be wasting a lot of water. This can not only harm the environment but also increase your water consumption.

Over time, corrosion can also cause damage to flush valves. This causes a gap between the tank’s seal and the bowl, which allows water to leak from the tank in a similar way. It is an important item that can cause problems with toilet flush systems. There are many other possible causes for flush valve damage: a worn tank ball, damaged flush valve seat, split or holed-in overflow pipe; damaged gasket underneath the flush valve; foreign material stuck under the ball or flapper.


To replace a toilet valve, you will need to remove the tank and install the valve. It doesn’t seem like too much work.

It is a good idea to replace the flush valve as well as the tank to bowl gasket, toilet flapper, and bolts.

Toilet tank repair kits can be purchased for less than one part. You can use a new kit for five or more years.

A flush valve replacement costs between 10-20 dollars

Wrapping up

You might be able to identify minor problems with commercial toilets once you have mastered the basics of the toilet flush valve. Also, you can find other tips and hints about commercial toilets in our commercial toilets blogs.

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