10 Common Toilet Fill Valve Problems You Didn’t Know Exist!

Toilet fill valves are responsible for filling up the toilet tank with water after each flush.

As such, any problem with this component can cause major disruptions in the normal functioning of your toilet.

toilet fill valve problems

In this article, we will take a look at 10 of the most common toilet fill valve problems and their respective solutions.

If you've encountered any of the issues outlined below, read our toilet fill valve repair guide to fix the issue for good.

Toilet Fill Valve Problems

Here are the 10 most common toilet fill valve problems that shouldn’t be left unattended:

A Constantly Running Toilet

A toilet that won’t stop running is a very common fill valve problem. It occurs when water flows constantly into the overflow tube. This occurs because the fill valve is broken, lower than the overflow tube, or the toilet float is misadjusted.

To address a constantly running toilet, check the height of the fill valve. The fill valve should be about an inch higher than the overflow tube else there will be a constant overflow.

What to Do?

Adjust the height of the fill valve appropriately to fix the problem. This video will help you to adjust the height of a fill valve.

If the fill valve is broken, replacing it with a new one is the only solution.

If the tank’s water level is too high that water spills into the overflow tube, the toilet float is misadjusted. Look out for the long plastic screw along the float ball/cup/cylinder.

Turn this screw slowly in a counter-clockwise direction to lower the float ball/cup/cylinder. This will, in turn, lower the water level, preventing an overflow.

Toilet Tank Refilling Slowly

The toilet tank gets refilled via the fill valve and should get refilled within 1.5 to 3 minutes.

However, if refilling takes an unusually long time, the fill valve is clogged. This is a common toilet valve problem caused by a hard water supply.

How to Fix?

Loosen the fill valve by turning it gently anticlockwise, you may need to loosen the lock nut.

Raise the fill valve to remove it and check for the buildup of mineral deposits and debris.

Remove them using a brush and vinegar.

Install the fill valve back again after removing the clogs.

Toilet tank refilling slowly can also be caused by a partially closed water supply valve.

If the water supply valve is partially closed, this will cause low pressure in the toilet tank, causing the fill valve to fill the tank slowly.

Check the water supply valve if it’s partially or fully closed by turning it slightly clockwise.

If it doesn’t turn clockwise or turns just a little, then it’s partially or fully closed. Open the water supply valve by turning it completely anticlockwise.

Low Water Level in The Toilet Tank

The water level in the toilet tank should get to about a half-inch below the overflow tube.

Anything lower than this will cause weak/incomplete flushing, anything higher than this will cause a running toilet.

This problem is usually caused by a misadjusted float ball/cup.

Along the float ball/cup/cylinder, there is usually a long plastic screw. If the water level is lower, turn this screw slowly clockwise.

This will raise the float ball/cup/cylinder and, in turn, raise the water level. If the water level is higher, turn the screw anticlockwise. Make sure that the adjustment is appropriate.  

Toilet Float Issue

Occasionally the toilet float can get stuck or hardened, especially ballcocks. When the toilet float sticks/hardens, it will not gauge the water level in the tank properly. The toilet tank may either overflow or not fill properly.

Sometimes clogs and mineral deposits are responsible for this and removing the clog should correct the issue.

Toilet float is made of plastic and may deteriorate over time, causing it to malfunction.

If the toilet float is worn out, it should be replaced with a new one.

Damaged fill tube

A fill tube is a small hose that connects the fill valve to the overflow tube. The small hose is an important part of the fill valve assembly.

It signals the overflow tube how much water to allow into the toilet bowl after flushing.

The fill tube is clipped to the tip of the overflow tube and goes only slightly into the overflow tube.

With time, the fill tube can deteriorate and/or get unclipped from the overflow tube.

If the fill tube is damaged, the toilet bowl will either overflow with excess water or have less water.

How to Fix?

There is no practical way to fix a fill valve when it’s damaged. You’ll need to replace it with a new one.

Misadjusted/Malfunctioning Pressure Sensor

This problem is only common with pressure-activated fill valves. A pressure-activated fill valve has a pressure sensor instead of a floating mechanism.

The sensor ensures that the water in the toilet tank is maintained at a certain level.

This pressure sensor can malfunction over time, affecting the normal water level in the toilet tank.

If your toilet uses a pressure-activated fill valve, carefully check the pressure sensor. Is it misadjusted or malfunctioning? The best solution to a malfunctioning sensor is to get a new pressure sensor.

A misadjusted sensor needs to be adjusted properly.

Clogs/Buildups in the Fill Valve Assembly

The fill valve assembly is very sensitive to the water passing through it. Depending on the type of clog, the fill valve can partially or fully clog up.

This will prevent the free flow of water into the tank. The clog can be dirt, debris, or the buildup of mineral deposits. The clogs/buildups can occur on any part of the fill valve assembly.

This problem usually leads to a slow or irregular flow of water into the toilet tank.

Sometimes, the clog can completely block the flow of water into the tank, preventing the toilet from refilling after flushing.

You need to remove the clogs from the fill valve assembly but you must find out exactly where the clogs are.

Remove the fill valve assembly and carefully check for clogs in it.

Poke out the clogs and use a brush and vinegar to wash off clogs from the assembly.


The fill valve assembly may deteriorate and leak with time. When this happens, the fill valve will continue to leak water into the toilet tank even when it’s filled.

Sometimes, clogs and mineral build-ups may prevent the valve from shutting off completely. Any of these will lead to a toilet overflow or running toilet.

If the leak is due to clogs/buildups, remove the clogs/buildups from it. If the leak is due to a deteriorating fill valve assembly, get a new one.

Broken Part

Over time, any part of the fill valve assembly may wear out and break as they are made of plastic.

Some metallic parts may corrode and eventually break off. This will cause the fill valve to malfunction.

The only solution is to replace the broken part. However, if the broken part is not replaceable, replace the entire fill valve assembly.

Loosened/Worn-out locknut

The last common problem on our list is a loosened/worn-out locknut. Although this problem affects the fill valve, it’s external to the toilet tank.

The locknut is located under the toilet tank and secures the fill valve assembly tightly to the tank.

If the locknut is loosened/worn out, water will leak through the locknut to the toilet floor.

Depending on how loosened the locknut is, the fill valve assembly may wobble inside the toilet tank. This will affect the normal functioning of the fill valve assembly.

For a loosened locknut, the best solution is to tighten the locknut tightly by turning it in a clockwise position.

A worn-out locknut needs a replacement. Make sure that the replacement locknut is of the same size and model as the worn-out locknut.

To Conclude

These are the 10 most common toilet fill valve problems that you may encounter.

Regularly check your fill valve for any of these problems and take appropriate action to nip them in the bud.

Preventative maintenance will save you a lot of time, effort, and money in the long run.

I hope this article was helpful. Thank you for reading!

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