Dual Flush Toilet Not Filling
Kristina Davis

You might not think that something as simple as your toilet could give you any trouble, but a dual flush toilet not filling is one of those unexpected problems.

A dual flush toilet has two levers or buttons to flush different amounts of water, one for liquid waste and one for solid waste. 

If you've ever gone to flush and found that your dual flush toilet isn't filling up, you know how frustrating it can be! 

In this article, we’ll show you some easy solutions to this problem so you can get your toilet working properly again in no time.

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The simplest solutions to this problem are to fix water pressure, faulty float ball, faulty flapper or a leaking toilet bowl. Having a dual flush toilet is great for saving water; with these solutions, it should be up and running again. 

Low Pressure

low pressure

If your dual flush toilet isn’t filling, it could be due to low pressure.

This is a common problem, especially if you live in an area with high water tables or have an older home.

The toilet tanks shut off without filling due to low water pressure.

There are a few easy solutions to this problem:

Check Water Pressure Rating

check water pressure

The toilet manufacturer usually stamps the water pressure it needs onto its tank.

Before you do anything else, check the rating of your home’s water pressure against the requirement from the toilet.

Contact a plumber or your local water company if your home has insufficient water pressure to meet the demand.

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Check the Main Line

Check to see if there’s any water coming out of the taps. If there isn’t, it could be your home’s main pipe.

Check to make sure you’re receiving municipal water from your taps.

If no water leaves your property but enters it, then the low pressure is most likely due to a leak or blockage in the pipes inside your house.

Pressure Regulator 

check pressure regulator

Another option is to adjust the settings on your pressure regulator. This is typically located where your main water line comes into your home.

Adjusting the settings can increase the overall water pressure in your home, which should help your dual flush toilet fill up correctly.

Fix Failing Pumps

If you see that your water pressure levels are too low, it usually means your water pump is failing.

This problem could affect many renters in one building if the water pressure is low at the top of the building.

If this happens, you may think you need to check with each renter before determining if there is a leak and what part of the building the leak might be coming from.

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Faulty Float Ball

float ball

Many toilets today still use a toilet float ball, which can fail if part of the arm is faulty.

If you’re you’re wondering why is my dual flush toilet not filling, this could be the reason why. 

A float ball and arm control how much water gets into the toilet tank.

If you wear this out or adjust it incorrectly, then too much or too little water will go into the tank, leading to an overflow or an empty tank.

Adjusting the ball will let more water into the tank, which can fix many issues. 

Here’s how to fix it:

  • You have to bend the arm up slightly
  • After a few tries, it should work
  • Open the taps to allow for filling of the toilet
  • If it still doesn’t fill you may need to replace the float ball

Waterlogged Float Ball

It could also be because the float ball is waterlogged, and this will cause the toilet to not fill with water.

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Simply remove the ball from the tank and dry it off to fix this. Once it’s dry, please put it back in the tank and fill it up.

Clear out any excess debris or sediment clogging up the float ball. This should solve the problem.

Note: If you experience frequent problems with your floating arm, sometimes the best course of action is to replace it. 

With kits available at any local hardware store, this process can be completed DIY.

Flapper or Seal Trouble

flapper or seal trouble

It’s also likely that there’s a problem with the flapper or seal if your dual flush toilet is not filling.

Toilets rely on a simple design to function properly. When you flush, the handle lifts a rubber flapper or seal inside the tank.

A simple way to test it is to put your hand over the top of the tank and see if water starts to leak out when you flush.

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If it does, then you know there’s a problem with the flapper or seal.

How the Flapper Works

The purpose of a toilet flapper is to prevent water from running into the toilet when it isn’t in use.

Make sure the chain holding it isn’t caught and causing it not to close properly as it could leak. You may have to replace or shorten the chain from time to time.

If the flapper or seal is damaged, water can leak out of the tank and prevent it from refilling properly.

Consequently, if a flapper valve is old or worn out, it may leak due to corrosion.

Older metal flappers on older versions were prone to chrome chipping and the metal became rough and deformed when pressure was applied.

It is usually a pretty easy fix, and you can find replacement parts at most hardware stores

Flappers in Older Homes

rubber flapper

Older houses did not have rubber seals, so metal flappers were used. These workers are now being phased out for newer houses, and silicone is used instead.

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Rubber is not as strong but does give a perfect seal.

If your flapper valve gasket gets worn or hardened, it must be replaced before the flapper valve can be installed.

Faulty Toilet Bowl

faulty toilet

Another possibility may be that there is some damage to your toilet bowl.

A slow leak through a crack in the back of the toilet bowl can cause the water to drain out before it is able to reach the ideal level.

If this happens, your dual flush toilet won’t fill up anytime soon.

You will typically notice water on the floor if this leak goes undetected. Here’s how to solve this:

Turn off the Water Supply

Your toilet may collapse if it continues to fill with water. Turn off the water supply right away and avoid using your toilet.

You do this by turning the valve under it or the one in your bathroom.

The issue may result in adding more damage to your bathroom or possibly flooding other spaces with water.

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Whether you need to have your existing toilet repaired or if you need a new toilet installed, it’s best to call a professional plumber immediately.


debris in toilet tank

The water supply to your dual flush toilet isn’t always as clean as you think.

Debris, dust, and dirt may have entered the toilet and caused the fill valve to malfunction, which will also make the toilet tank not fill up.

If you have a fill valve malfunction caused by debris, you’ll need to clear it before your toilet starts working properly again.

Debris Screen

toilet debris screen

This screen is inside the tank, and it’s there to catch any sediment or debris clogging up the fill valve.

Over time, this screen can become clogged with sediment, preventing water from flowing into the tank. This is often a major cause of dual flush toilet tank not filling.

Here are some easy solutions to get your toilet valve working like new again!

  • Turn off the tap.
  • Remove the lid from the fill valve.
  • Check for any debris.
  • If you find any, remove them.
  • Clean out the dust on the valve using a brush
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Once you’re satisfied that everything is clean, put the lid back on, and open the taps to ensure the problem has been solved.

Note: To clean the debris screen, remove it from the tank and rinse it off with a hose.

Final Thought

When faced with a dual flush toilet not filling issue, it’s important to troubleshoot the issue as soon as possible to avoid inconveniencing your household members.

Check water pressure, then check to see if the valve is turned on and if it is, make sure it is properly installed.

If the float and flapper are not working properly, they may need to be replaced.

Additionally, ensure water flows into the toilet tank by checking for a clog or overflow.

Finally, ensure the toilet is connected to the sewer system by checking for a break in the pipe.