Is Your Toilet Whistling? Why and What to Do

Is your toilet whistling after flushing? That is definitely not normal. The only sound you would expect to hear from a toilet is the sound of water refilling the tank and the wastewater leaving the bowl.

A whistling toilet is caused by a blocked/damaged fill valve. This is as a result of a worn out gasket or clogging of the fill valve by mineral deposits or debris, restricting the flow of water and hence the whistling sound as water forces its way through the valve.


To fix a whistling toilet you should flush out debris from the fill valve and clean the gasket/seal. If the gasket is worn out or if you want a long-term solution you should replace the fill valve.

A whistling toilet is not dangerous but it is definitely irritating. It will not damage your toilet in any way or affect the toilet’s flush power unless the fill valve fails completely and you end up with a running toilet.

If you still have the old-school ball-type toilet fill valve (also known as a ballcock valve), now would be a good time to replace it with a modern fill valve.

How a Toilet Fill Valve Works

A toilet fill valve is the toilet tank part responsible for filling the tank with water after every flush. It is connected to the water supply hose from underneath the tank and is also connected to the toilet float inside the tank.

A toilet float basically controls the opening and closing of the fill valve opening. Old toilets have a ballcock connected to the fill valve using a lever while modern toilets have a small float connected along the vertical body of the fill valve.

The toilet tank is always full of water and at that time the float is usually at the top. At that time also, the fill valve opening is also closed.

When the toilet is flushed, the float assembly moves to the bottom of the tank, a move that opens the fill valve opening. As the water level in the tank increases, the float moves up until the water level is at its set mark and the float shuts off the fill valve opening.

Why Your Toilet is Whistling

Even us humans, we can’t whistle with our mouths wide open. To whistle, you need to bring your lips together and leave a small opening to force out air.

It is the same thing with a whistling toilet. It means that something is blocking the fill valve and therefore restricting water from entering the tank. As a result, water has to force its way through a small opening and hence the whistling sound.

If you live in an area with hard water, it is not unusual for mineral deposits to clog the fill valve leaving only a small opening which the water (since it is under pressure) will squeeze through and in the process create the whistling sound.

A worn out fill valve gasket/seal will also result in the whistling sound. The worn out gasket will vibrate as water passes through and hence the whistling sound.

How to Fix a Whistling Toilet

The best solution to a whistling toilet is to replace the fill valve. The good thing is that a fill valve is cheap and also easy to replace. You will not need to hire a plumber to do it.

If you are not ready for a replacement, you can try to fix it and see if that works. Here are therefore the 2 methods to stop a toilet from whistling:

1. Clean the Gasket

Here is how to clean and flush out debris and mineral deposits from a toilet fill valve:

  • Turn off the toilet shut off valve. That is the knob on the wall behind the toilet. Turn it clockwise all the way.
  • Flush the toilet and hold the lever down to remove as much water as possible from the tank.
  • Remove the toilet tank lid and place it away in a safe place where it cannot fall off and crack.
  • Locate the fill valve. It is usually on the left side of the tank.
  • Grab the top cap (usually of a different color from the fill valve body) and the float and turn it 1/8 turn counterclockwise to remove it. If you have a ballcock you may need to disconnect it using a screwdriver.
  • You will see seal/gasket under the cap. Remove it and clean it to remove any debris.
  • Check if the seal is in good condition or if it is worn out. If it is worn out you will have to replace the fill valve.
  • Next hold a cup (when inverted) over the fill valve and turn on the toilet shut off valve. The idea here is to force the water pressure to flush out debris from the fill valve while using the cup to prevent water from splashing on you. Do that for a few seconds
  •  Put back the top cover by turning it 1/8 turn in the opposite direction.
  • Flush the toilet a few times and check if the whistling stops.

3. Replace the Toilet Fill Valve

The best toilet fill valves apart from those made by your toilet manufacturer are those made by Fluidmaster or Korky. You will not go wrong with a toilet fill valve from one of these universal fill valves manufacturers.

This is how to replace a toilet fill valve:

  • Turn off the toilet shut off valve.
  • Flush the toilet and hold the flushing lever down to remove most of the water.
  • Remove the toilet tank lid.
  • Use a sponge to soak any remaining water at the bottom of the tank.
  • Place a bucket or container under the connection between the water supply hose and the tank. This is for draining the water still in the hose.
  • Disconnect the water supply hose by turning the coupling counterclockwise. Use your bare hand only as using a wrench can deform it. Only use a wrench if the connection is too tight.
  • Disconnect the fill valve mounting nut as well. This nut holds the fill valve firmly against the toilet tank.
  • Disconnect the fill valve clip from the overflow tube and lift it out of the tank.
  • Adjust the height of the new fill have. Fill valves can be adjusted to fit tanks of different heights. Ideally, the top of the fill valve (the cap) should be about 3 inches higher than the top of the overflow tube.
  • To adjust a fill valve you only need to hold the top part with your left hand and turn the shank counterclockwise with your other hand to increase its length.
  • Once you have properly adjusted the fill valve, insert it in the opening at the bottom of the tank and tighten it using the mounting nut from underneath the tank.
  • Connect the water supply hose to the fill valve and also hook up the fill valves refill tube to the overflow tube.
  • Turn on the toilet shut off valve.
  • Flush the toilet to conform that the whistling noise has stopped.
  • Put back the toilet tank lid.

And basically that is how to fix a whistling toilet. I hope this guide was helpful.

Related: How to increase a toilet’s flush power.

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