How To Replace A Toilet Fill Valve

There comes a time when you need to say goodbye to your toilet's fill valve. While it may have provided years of unrecognized service in faithfully refilling your toilet tank, it may have eventually stopped performing its function.

Fill valves can fail because of worn parts or from an accumulation of minerals from your water supply that interferes with the ability of the float to control the flow of water into the tank.

While you can disassemble your toilet fill valve in order to replace defective parts or clean the float mechanism of mineral deposits, it's easy and inexpensive to simply replace the entire fill valve.

What you will need

  • Fill valve
  • Adjustable wrench
  • Teflon tape
  • Sponge or rags

Removing the defective valve

You will begin by shutting off the supply valve that controls the flow of water into the supply line. This valve is located close to the floor on the left side of the toilet (facing the toilet).

When the valve is fully closed, you will flush the toilet several times to remove as much water as possible from the toilet tank. Use rags or a sponge to absorb all remaining water from the tank.

You will then use an adjustable wrench to disconnect the water supply line from the bottom of the old fill valve. You will next loosen the larger nut that holds the fill valve in place inside the toilet tank. The nut should only have been tightened by hand, so remove the nut and lift the old fill valve from the toilet tank.

Installing the new fill valve

You will first wrap a few layers of Teflon tape in a clockwise direction around the threaded end of the fill valve, then place the end of the valve through the opening of the toilet tank.

Hand tighten the large nut that holds the valve in place until it is secure against the bottom of the tank. Do not use a wrench to tighten it or you may crack the tank. 

You will then reconnect the supply line, tightening the nut with the adjustable wrench.

The next step will involve adjusting the fill level for the tank by twisting the fill valve counterclockwise until the top rim of the fill valve is one inch below the top of the overflow tube, which is a hollow tube in the center of the tank.

This will keep the water level slightly below the level of the overflow tube, which keeps the tank from overfilling and overflowing onto the floor.

When this is done, turn on the supply valve and watch the water level in the tank to ensure that the fill valve is adjusted properly.

You can raise the water level by turning the fill valve counterclockwise and lower the level by turning the fill valve clockwise. Just remember to keep the level below the top of the overflow tube or your toilet fill valve will run incessantly in a van attempt to fill the tank beyond the level of the tube.

For assistance, talk to a plumber.