Why Is My Toilet Hissing?

2017 Sep 11
Posted in: Plumbing

If you hear your toilet hissing, you likely have one of the following 2 problems:

  • Debris trapped in the fill valve
  • A damaged float

We’ll explain the 2 problems listed above, why they create a hissing sound and what you can do to fix it.

Need a plumber to repair your hissing toilet ASAP? Just contact us and we’ll send one right away.

Problem #1: Debris trapped in fill valve

Your fill valve is the tall device that sits to the left of your toilet tank. This valve is connected to your home’s water supply and fills the toilet tank back up with water after every flush. 

When working properly, your fill valve should shut off as soon as the water in the tank hits a certain level. 

But sometimes, sediment or debris in the water can get stuck in the opening of the fill valve. This prevents the valve from shutting off completely and forces leaking water through a restricted opening which causes a hissing noise

What to do: If you’re handy, you can try removing the fill valve cap and flushing out any sediment that’s accumulated inside. If the cap is particularly warped and damaged, follow this video to replace the cap altogether.

Otherwise, you’ll want to have a professional flush any sediment or dirt out of the fill valve.

Possible problem #2: A damaged float

Your toilet’s float tells the fill valve when to turn on and off. The float is designed to rise and fall with the water level in the tank. 

For example, after the toilet is flushed, the float sinks, triggering the fill valve to come on. And once the float rises to a certain point, it triggers the fill valve to turn off the water.


Your toilet float may look slightly different. For example, older models have a long arm connected to a float that resembles a large ball or balloon.

But sometimes, certain problems prevent the float from rising high enough to shut your fill valve all the way off. And as water tries to escape a small opening, water pressure inside the valve builds, creating a hissing noise.

Some problems that can prevent a float from shutting off the fill valve include:

  • Water getting into the float and affecting its buoyancy
  • Debris blocking the float’s upward movement

What to do: Have a professional examine your toilet's float. If the float can’t be repaired, they’ll need to replace the entire fill valve.

Need help from an AZ plumber?

If your toilet is still making that strange hissing noise, just contact us.

We can send an experienced plumber over right away to find and fix the issue.

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