Why Does My Toilet Whistle? (and how to stop it)

Over time and frequent usage, we all get to know the sound of our toilet when it is flushed. This knowledge can become invaluable because if we start to hear any unexpected noises, we’ll soon realise they could be the start of a problem. We can then get that problem remedied as soon as possible.

In most cases the cause of a whistling toilet is a worn or damaged fill valve or gasket.

Fixing this is a relatively simple task and can be tackled in one of two ways;

  1. Replace the gasket
  2. Replace the entire fill valve

These are both fairly inexpensive parts to replace as modern toilet components tend to be made from plastic and can be found at almost any DIY or hardware store.

If Your Toilet Is Whistling It Needs Attending To Immediately

Once the whistling sound in your toilet has become loud enough to reach your ears, it needs to be dealt with. There’s a distinct possibility that the fill valve could fail at any time. Or it could last for weeks, but do you want to risk coming home to a bathroom flood?

The Easiest Way To Fix A Whistling Toilet

For those of you with limited or no experience in replacing parts of the toilet, we’d recommend replacing the whole valve. This is because it doesn’t involve dismantling the fill valve. All you need to do is simply unscrew the old valve and replace it with the new one.

How To Replace A Toilet Fill Valve To Stop The Toilet Whistling

You will need a replacement fill valve, a flat headed screwdriver and basic DIY skills. Follow our step by step guide to ensure you get it right first time.

  1. Turn off the water supply to the toilet
    On most modern toilets there will be a shut off valve on the inlet pipe under the cistern somewhere. All you need to do is turn the screw into a horizontal position to prevent water entering the cistern. If you can’t locate the shut off valve you’ll need to find the stopcock for your home (often under the kitchen sink) and turn it off. 
  2. Remove any remaining water from the cistern
    Once the water supply to the cistern is turned off, flush the toilet to empty the cistern of water, don’t worry about any slight residue at the bottom of the cistern as this won’t affect the replacement of the fill valve.
  3. Remove the old fill valve
    Unscrew the plastic nut at the bottom of the fill valve this will release the fill valve from the toilet.
  4. Fit the new fill valve
    Simply replace the old fill valve with the new fill valve and tighten the plastic nut to hold it in place.
  5. Adjust the new fill valve to the correct level
    This might take some fiddling around once the water is turned back on, but in many cases it’s just a simple case of making sure everything is set up exactly as it was before.
  6. Turn the water supply back on
    Either turn the stopcock back on or turn the screw on the supply pipe to the vertical position.
  7. Check that the cistern and fill valve are working correctly
    Once the water has been turned on again, allow the cistern to fill with water. Firstly, you shouldn’t hear that annoying whistle anymore, and secondly, check to see that the water level is correct in the cistern once it is full (enough to create a good flush, but not so much as to cause it to spill over the top of the cistern).

How Does The Fill Valve Work?

Once you flush your toilet, the cistern begins to refill with water, and would continue to fill unless there was something to prevent it. That something is the fill valve which is connected to a float assembly. That’s the big (usually) orange ball-like thing. As the water level rises, so does the float assembly.

Once the float reaches a previously determined point, it closes the fill valve which shuts off the water supply. Until the next flush which lowers the float assembly, allowing more water to enter the cistern via the fill valve and the whole process starts all over again.

What Causes The Fill Valve To Whistle?

Before you take the old fill valve out, have a close look at it. Does it have a build up of calcium? This will look like an off-white crusty deposit and could be the cause for the fill valve to start whistling. It will need to be replaced still, but you now know your area is served by hard water.

If The Fill Valve Isn’t Whistling What Is?

If the fill valve has no calcium build up and once you have removed the cistern lid and flushed the toilet, you can tell the noise is coming from somewhere else. It will probably be coming from the fill pipe to the cistern. This can become clogged or partially clogged with calcium.

This is potentially a more difficult job, so unless you have a good level of DIY skills we’d recommend calling in a plumber. However if you feel you want to tackle this yourself, the first thing to do is turn off the water supply to your home using the stopcock.

Then with a pipe wrench remove the fill pipe (usually copper) and either try to remove any calcium build up or replace with a new pipe. This is why we suggested you might need a plumber as you might need to bend the pipe to get it to fit exactly.The chances are you won’t have the necessary tools for proper pipe bending etc.

Or you could buy a flexi-pipe which should bend into the shape you need. This will probably be the easiest way to replace the fill pipe. These consist of a connector at each end and a piece of flexible pipe in the middle. You simply connect either end to the connections that the old pipe was attached to using your wrench.

Our Recommendations

We would suggest that fitting a new fill valve is a job that even someone with a very limited knowledge of DIY could manage. However, fitting a new water fill pipe to the cistern, is far more involved and probably best left to a professional plumber.

Frequently Asked Questions

Why is my toilet making a high-pitched whine?

If your toilet is making a high pitched whine, it is most likely to be the fault of the fill valve. Either the fill valve itself, or the fill valve gasket is faulty. As a new fill valve is relatively inexpensive and easy to fit, we recommend replacing the fill valve. The new one will come complete with the gasket intact.

What happens if you don’t fix a whistling toilet?

If you don’t fix a whistling toilet, the fill valve will wear out sooner or later and flood your bathroom and potentially your entire home. If the fill valve packs up altogether, water will continue to flow into your cistern and eventually all over the bathroom floor and so on.

Why does my toilet make a loud whistling noise?

If your toilet is making a loud whistling noise, the fill valve needs replacing. As the fill valve ages, some of its internal components wear out. This will cause the fill valve to whistle as water runs through it. Failure to replace the faulty fill valve could potentially cause your home to flood.

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