Toilet Pulses When Filling – Fixed

Few things are more irritating than having to deal with a toilet that seems to be “gurgling” because of the pulsing sound it makes when filling. So naturally, you’ll want to know why your toilet pulses when filling and what you can do to solve this problem.

Your toilet pulses after flushing due to a blocked or damaged valve, a blocked ballcock assembly, air stuck in the waterline, or a worn-out washer. The fix may be replacing the flush valve or ballcock assembly, flushing out trapped air, or fixing damaged washers, depending on the cause.

toilet pulses when filling

This article will guide you through the common problems that cause a toilet to pulse when filling. I’ll also discuss how to address each potential cause in detail. Let’s get started. 

1. The Flush Valve Is Blocked or Damaged

The flush valve is located inside the toilet cistern. Its job is to drain the contents of the toilet system into the sewer system. If the flush valve gets damaged or blocked, you’ll notice a water leakage or a deep, pulsing sound.

It’s important that you don’t confuse the noise caused by a faulty flush valve with the sound caused by a malfunctioning fill valve. A fill valve causes an incessant hum 一 it’s one of the main causes of humming in toilets 一 that’s different from the pulsing caused by a compromised flush valve. 

flush valve

How To Fix

To insert the new flush valve, follow these steps: 

  1. Turn off your toilet’s water supply.
  2. Open the toilet tank and locate the flush valve. 
  3. Remove the valve by turning it in an anti-clockwise direction.
  4. Check whether the flush valve is blocked or damaged if you notice any cracks, you’ll have to replace it. 
  5. Replace the old flush valve with a new one, and put it back in position by screwing it clockwise. 
  6. Test the flush tank to check whether the sound is gone.

Note that this is a somewhat simplified version of the replacement process meant for individuals with a fair understanding of toilet plumbing. If you need a step-by-step walkthrough, check out this video:

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2. The Ballcock Assembly Is Blocked or Damaged 

The purpose of the ballcock assembly is to refill and regulate the water in the tank after usage. If the ballcock assembly gets blocked or damaged, your toilet will start producing a pulsing sound because of overflowing water.

How To Fix

The best way to fix a damaged or broken ballcock assembly is to replace the whole assembly. 

Start by shutting off the water to your toilet. Toilets are usually supplied water by a tube on the floor and behind the toilet. In some homes, this tube is wall-mounted.

Simply turn the knob to cut the water supply and flush the tank so that it is empty. Remove the lid from the tank and use a dry towel to wipe the water left inside the tank. 

You’ll find the ballcock clasped inside the water tank with two large nuts. Use a screwdriver to loosen the nuts, remove the damaged or blocked ballcock, and replace it with a new one. 

3. Air Is Stuck in the Waterline

If there is constant bubbling in the plumbing after flushing the toilet, chances are air or some sort of blockage is stuck in the toilet. Fortunately, you can easily remove an air blockage with a plunger. 

How To Fix

Fill the toilet bowl halfway and place the brim of the plunger on the draining hole. Make sure that you have sealed the plunger correctly. Next, rapidly force it up and down several times until the water start’s draining. 


When the water drains completely, flush your toilet again to check if you’ve gotten rid of the blockage or air stuck in the waterline. You can also use this method if there’s dirt blocked in the waterline. 

If the waterline is too clogged to fix, you might have to replace it. Here’s a quick video guide on how to do that:

4. The Valve’s Washer Is Worn-Out

The valve washer is a component inside the toilet tank that prevents leakages and ensures the right amount of water enters the toilet tank. It allows water to enter the tank after each flush and shuts off the supply when it’s full. 

Sometimes, the valve washer can get damaged and stop working. Other times, it’s just a matter of this all-important part reaching the end of its service life. Either way, you’ll have to replace the valve washer. 

How To Fix

To fix the valve washer, begin by shutting off the water to the toilet and allowing it to drain. 

Next, remove the lid and locate the fill valve inside the tank. The valve washer is a thin white or black rubber or plastic ring that prevents valve leakages. 

You’ll have to unscrew the nut that attaches the valve washer to the water supply. Once that’s done, remove the worn-out valve washer and replace it with a new one. Double-check to ensure the new valve is securely attached to the water supply line. Otherwise, you’ll be dealing with leakages pretty soon.

5. The Tank’s Water Level Is Too High

Your toilet tank’s water level should be 1 (2.5cm) to 2 inches (5cm) inches below the overflow tube and the flush valve. If it gets too high, your toilet will start making a pulsating sound. This usually happens when the tank overfills after a flush due to a compromised ball-and-arm.

the tank’s water level is too high

How To Fix 

To get rid of excessive water from a toilet, you’ll have to adjust the ball-and-arm float properly since it’s the main reason why your toilet tank may be overfilling. 

Here’s how to do it:

  1. Turn off the water supply to the toilet tank and flush it. This will allow the water to drain sufficiently.
  2. Remove the lid of the tank. You’ll notice that the ideal water level is not below 1 (2.5cm) to 2 inches (5cm) of the fill valve. 
  3. Fix the height of the float to readjust the water level. Use a screwdriver to rotate the screw above the float counterclockwise. This should fix the amount of water in the tank.

Here are the steps for fixing a cylinder-shaped float: 

  1. Turn off the water supply.
  2. Flush the tank to drain the water and remove its lid. 
  3. Inside the tank, find the adjustment screw that connects the float and fill valve. 
  4. To fix the water level, turn the screw counterclockwise until the water level is 1 (2.5cm) to 2 inches (5cm) below the fill valve. 


If your toilet makes a pulsing sound after flushing, it’s usually because of a blocked or damaged flush valve, ballcock assembly, worn-out valve washers, a high water level in the tank, and air stuck in the pipeline. 

Thankfully, you don’t need to call a plumber to help with these issues. In most cases, you just need to replace the old hardware.