Why You May Hear Noises Through Your Walls When the Toilet Flushes

Alison Kasch
Written by Alison Kasch
Updated September 28, 2021
Modern bathroom with walk - in shower
Iriana Shiyan - stock.adobe.com

If you hear a ruckus when the toilet flushes, that means there's something awry

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Noises from your plumbing after flushing the toilet are annoying, if not alarming. Not to mention, it can be pretty embarrassing to have your toilet notifying the entire house with every flush. So, what’s the deal with all the noise from the pipes when the toilet flushes? Here’s a little insight into what causes them and what you can do to fix the problem.

1. There’s a Groaning or Vibrating Noise When Flushing the Toilet

When you hear a vibrating noise from your pipes when the toilet flushes, this usually points to an issue with the fill valve. This piece is the part of your toilet that refills the water tank. It might also sound like a foghorn or groaning noise that continues for around 30 seconds after you flush.

The Problem:

Once the toilet tank gets filled, a small diaphragm in the fill valve pushes down and cuts off the water flow. This diaphragm is made of soft, flexible material—typically rubber—which creates a tight seal to prevent the tank from overfilling.

Over time, though, that diaphragm can become stiffer and less malleable. This change causes it to rattle around when the incoming water hits instead of staying tightly sealed as it normally would. If you’re hearing a humming or vibrating sound, that’s likely the source.

The Fix:

You can diagnose a fill valve issue by following these steps:

1. Take the lid off the toilet tank

2. Flush the toilet

3. Lift the ball float to cut off the flow of water

If the sound stops after you do this, there’s an issue with the fill valve.

Once you’ve pinpointed the problem, you can get rid of that vibrating noise by replacing the fill valve. This task is a simple DIY toilet repair if you’re up for it. The new valve should have instructions for replacement. If you’re not comfortable handling this on your own, a local plumber can always assist you.

2. There’s a Knocking Noise from the Pipes When the Toilet Flushes

Plumber fixing the toilet
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A knocking or hammering noise in your pipes is a telltale symptom of water hammer. This phenomenon can also sound like a loud thud after flushing the toilet.

The Problem:

When you flush the toilet, it opens a valve to allow more water in. Water hammer happens when the valve suddenly shuts off, resulting in water with no other place to go. This incident causes the excess water to hit the walls of your pipes at high speed, resulting in a ratting or hammering sound.

The Fix:

Water hammer is a noisy nuisance that can damage your pipes over time if left unaddressed. You can fix the issue by having a plumber install a water hammer arrestor, which absorbs the shock of the sudden rush of water.

3. There’s a Rushing Water Sound When Flushing the Toilet

Hearing a running water noise usually means the tank is constantly filling. This sound might indicate a leak within the tank, which can result from a few different causes.

The Problem:

A running water noise when flushing the toilet might mean there is water leaking from the tank into the bowl. 

It could also point to one of these issues:

  • Your fill valve is faulty.

  • The float in the toilet tank is set too high.

  • The chain that connects to the toilet handle is too tight.

Either way, this is important to address to prevent your toilet from wasting water.

The Fix:

First, remove the lid from the tank and check if the float is higher than the fill valve. If it is, then adjusting the float should fix the issue.

If that doesn’t fix the problem, look at the chain. It might be too tight, which would prevent the flapper from sealing the hole properly. There may also be too much slack, causing the chain to tangle. If you notice any of these issues, try adjusting the chain by removing its clip to the toilet handle and increasing or decreasing the length.

Not having any luck with these fixes? There might be parts that require replacement. Call in a plumber to have a look.

What to Do About Noisy Pipes When Flushing the Toilet

Luckily, a noise from your pipes when the toilet flushes isn’t always a death rattle. Many of these issues are repairable by fixing or replacing small parts. However, if there are issues with leaking, efficient water use, or broken components, these are good reasons to replace your toilet. Get in touch with a plumber to learn your options.

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