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Why does My Toilet Make A Hissing Sound after Flushing

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Why does My Toilet Make A Hissing Sound after Flushing

why does my toilet make a hissing sound after flushing

The hissing noise from toilet is a common problem, and when it starts, it seems like a small problem you can ignore. After all, you can only hear a slight hissing sound when you get close to the toilet.

However, this problem is not only annoying, but it can lead to more water usage and high water bills due to constant drainage. In this post, we’ll walk you through all the mechanisms to help you better understand why toilet makes a hissing sound after flushing and how to fix it.

Why does my toilet make a hissing sound after flushing

The snake-like hissing noise you hear from the toilet is due to air going through the hose into the tank. Usually, you will notice the toilet hissing when you flush. This is because excess water or air enters the tank through the hose when it should be cut off.

Or, it could be because hard water deposits or sediment particles have settled in the valve and partially blocked the flow of water to the tank. As a result, the water pressure in the valve increases, forcing the water out in a narrow stream and causing a worrying hissing sound.

Potential problem aites in a hissing toilet

Because the hissing toilet has so many components, there are many potential problems sites that could cause the toilet makes a hissing noise.

Fill Valve

Over time, sediment and debris can build up on the interior wall of the toilet and deteriorate the fill valve seal causing it to stop working. This allows water to seep through small openings creating a hissing sound. Also, a broken fill valve will cause water to run without stopping in the tank. This causes excess water in the overflow tube or overflow pipe resulting in the hissing noise.


If the float is malfunctioning, it means that it is not turning off the water when the tank has refilled. Therefore, the float will lift the chain on the flapper breaking the seal. When water gets between the flapper and the seal, this leaking water can cause a hissing sound.


A flapper that is in good shape will fit the seal in order to prevent water from seeping through. The flapper is rubber and over time, this can deteriorate or sediment can build up. Either way, the seal is not tight allowing excess water to leak through small openings.

Flapper Chain

The flapper chain attaches the flush valve assembly to the seal. This chain should be the correct size. If the chain is too long, the chain can slip below the seal causing the water seepage. If it is too short, the flapper will not fit against the seal.

Water Supply to the Toilet

Uneven water supply from the water flow lines may also cause a hissing sound as the water tank is refilling.

Diagnosing the Problem

We don’t want you to take your whole toilet apart to find the water leaking culprit. Instead, you can test each component to see which one it is. First, if the problem is the water supply, you will hear the noise when the toilet is flushing. Also, you will see the toilet slow flushing or not flushing all the way. Next, check the fill valve. If this is blocked, the toilet will fill without stopping.

Also, examine the float to see if there are any puncture holes that are causing it to take in water and sink. Further, check the flapper over the seal by closing off the water supply, draining the tank, and unscrewing the flap valve. If it seems dry and brittle or is dirty, this may be the problem. Last, while the tank is dry, check the flapper chain to make sure that it is the proper length.

How to fix a hissing toilet

In most cases, fixing the hiss problem is simple. Even an amateur plumber can handle this. If the prospect of tinkering with your toilet to fix the problem puts you in a bind, it’s best to have a professional plumber do the trick.

Check fill valve or float

The fill valve is a potential culprit of the problem. First, turn off the water supply to the toilet. Then, empty the tank by flushing the toilet. After the tank is empty, remove the valve cover and valve seal. Look for debris on seals and check for small mineral deposits or deposits that may be causing the problem. If there is visible debris, clean it with a cleaning solution designed for mineral or calcium deposits.

Check the bezel

If the fill valve has no problem, then check the flapper. This can be the cause of the hiss, especially if it’s not right and continues to let the water flow when it shouldn’t. Rinse with water (or vinegar if mineral deposits are present) and look for warped or deformed parts. Then check the chain for damage. If it’s the wrong length, it may hold up the baffle and keep the water flowing. Replace as needed.

Replace Inlet Valve Assembly

In some cases, the entire inlet valve assembly may wear out. If this is the case, you may need to replace the entire assembly. Each inlet valve has a slightly different design, so they separate in a different way.Check the manufacturer’s website for removal instructions, then follow the manufacturer’s instructions to install the new one. You can usually buy replacement components from the manufacturer’s website, but you can also find a match at your local hardware store.Typically, inlet valve replacement kits include all the parts needed to install the valve, as well as installation instructions and instructions for adjusting the tank level.

Closing thoughts

While the hissing from toilet issue probably won’t do any harm, it can add some impressive water bills. So if you’ve done your best and the problem persists, call your local plumber for help.



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