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Why does my toilet make a hissing sound?

Dec 06, 2021

A white toilet with the lid up that's placed in a bathroom corner that is making a hissing sound.

Noises from your toilet can be both annoying and concerning. Loud ones can keep you awake at night and lead you to worry about what expensive repairs might be headed your way. You can always call a professional you trust to handle strange toilet noises, but some sounds—like a hissing sound—may be easy enough for you to repair on your own.


Read on to learn a few of the common reasons why your toilet is making strange noises and get answers to your question, Why does my toilet make a hissing sound?”

Common Noises Toilets Make

Rest assured that noises coming from toilets are common. Not all of them mean something terrible. Here are a few of the most common noises that toilets make and the reason behind the sound.


Put your question, “Why does my toilet make a hissing sound?” to rest. More often than not, a hissing toilet is due to a deteriorating flapper—also known as a “flush valve”—or the fill valve. As your toilet tank fills, the fill valve stops it from overfilling. If that fill valve isn’t in the correct position or set at the right level, the water will overflow and cause hissing noises. If the flush valve is the culprit, then the flapper likely isn’t creating a proper seal. This means it will allow water to slip into the bowl, omitting a hissing noise. 

High-Pitched Squeal

Squeals or whines are normal noises for toilets to make as the toilet tank refills after a flush. This is usually because of a faulty float valve. Adjusting the mechanism can often resolve the issue or you can replace the valve for relatively cheap. 

Ghost Flushing

This might be a sound you only notice in the middle of the night when everything is quiet, getting you properly spooked. While it can seem creepy while you lay there in the dark, it’s actually nothing serious to worry about. When it sounds like your toilet flushed itself, what’s actually happening is your toilet tank is slowly draining. This is usually due to a faulty flush valve. As the float reaches a certain level, the water switches and it sounds as though the toilet flushed on its own. 


Gurgling noises can be the most obnoxious sound, and since the source of the issue isn’t easy to trace, they can also be bewildering and concerning. Gurgling can be due to a serious issue like a blocked sewer drain or even a blockage in the toilet. If you hear a gurgling noise from your toilet, don’t attempt to handle the issue alone or wait for it to get worse. Call in a plumber to resolve it. 

Water Hammer

This is a frequent noise that toilets make. It can also occur in various areas of your home’s piping. You may find a loud hammering noise after flushing due to the sudden stop in water flow. Since water is not compressible, it can crash and slam around when a pipe stops its rapid flow. There are some ways to reduce this noise but it’s nothing to be concerned about. 

How to Replace the Toilet Flush Valve

If you wish to stop your toilet from making hissing noises, then you likely need to learn how to replace the toilet flush valve. This is a fairly simple procedure that can be handled by a homeowner if desired. Rest assured you can call in a professional to handle the job and inspect for other issues if you want. Here are the steps:


  1. Remove the lid of your toilet tank.
  2. Shut off the water and drain as much out of your tank as possible by holding the flapper down. Sponge or towel-dry the remaining water out of the tank to make your work area clear.
  3. Disconnect the water supply tube from the toilet tank and remove the flapper chain from the lever arm. Also, remove the refill tube from the overflow pipe.
  4. Unscrew the bolts holding the toilet tank in place, then set the tank aside on a towel. From underneath the tank, you can unscrew the bolts holding the flush valve in place.
  5. Once the old flush valve is properly attached, replace it with a new one.
  6. Once the new flush valve is properly attached, you can replace the tank onto the toilet bowl in the way you removed it.
  7. Reattached the flapper chain to the flush arm and the fill tube to the overflow pipe.
  8. Reconnect the water supply when everything is secure, then turn on the water and attempt to flush.
  9. Check for leaks.

Feel Free to Call the Experts

If any of these steps seems confusing to you or if you simply don’t want to tackle the job yourself, our team of specialists at CroppMetcalfe is ready and happy to assist you. 


Get your flush valve replaced pain-free and rid yourself of that annoying hissing sound for good. We can help you with any of your regular plumbing maintenance or emergency plumbing needs.



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