Toilet Tank Not Filling or Filling Slowly

Why Is My Toilet Tank Not Filling?

Having a malfunctioning toilet tank can be quite a big problem. Not only will it make your utilities unusable, but it can also be a symptom of a more significant underlying issue.

That being said, it can sometimes be challenging to figure out what is causing your toilet tank to malfunction. If even one toilet tank fails to function correctly, the entire thing will stop filling.

Here is how to recognize the different causes of your toilet problem and the solutions you can apply if your toilet tank won’t fill.

Common Toilet Tank Issues

When working as intended, your toilet tank should only take a few minutes to refill after you flush the toilet. If that doesn’t happen, it means that there is something wrong with your toilet tank.

We will now explain all the different toilet tank problems that can cause it not to refill and how to solve each of them.

One or More of the Toilet’s Fill Valves is Malfunctioning

Each toilet tank has several fill valves that regulate its inner pressure and control the rate at which the tank fills. If just one of your toilet fill valves stops working, you will no longer be able to refill it.

The Toilet Fill Valve

The first of these is the toilet fill valve. This valve controls the amount of water supply the toilet tank gets. If this water supply valve is too low, the tank will simply stop filling before reaching the desired level.

The best way to resolve this issue is by simply replacing the faulty fill valve. Make sure, however, that your new fill valve is compatible with your toilet tank.

Alternatively, if the fill valve is screwed too tight and not malfunctioning, there is an even more straightforward fix. Screw counter clockwise to allow the fill valve to let in more water, raising the water valve in the tank.

The Float Valve

The second valve each toilet tank has is the float valve. This valve is controlled by a toilet float ball connected to the arm and raised as the water level is adjusted. This float arm usually connects to the left side of the tank and can be controlled using the flush cable.

This float ball is often replaced by a float cup in more modern toilets, but its function and the way it is connected to the valve seat remain the same.

The float valve ensures that the tank water fills properly while also preventing excess water from entering the tank and protecting it from overflow.

The Flush Valve

Finally, each toilet will also have a flush valve. This valve controls water discharge from the tank when you attempt to flush the toilet. This valve is governed by the flush lever and is essential to your toilet’s tank.

When the flush valve malfunctions, it makes flushing properly impossible. With the drain hole closed, the water cannot leave the tank, breaking the flush cycle.

When this happens, the best thing to do is to call a professional plumber rather than try to fix the problem yourself.

Overflow Tube Issues

An overflow tube is an essential part of your toilet tank. It transports excess water directly down the toilet bowl and into the sewer line. This large tube helps avoid overflowing, keeping your bathroom from flooding in the case of a misadjusted float arm 0r massive water pressure.

A cracked overflow tube compromises the entire system, and if allowed to break completely, it can flood the bathroom. If this happens to you, the preferred solution is to hire a professional handyman to fix the tube assembly.

Fixing the pipes requires special equipment and a skillset you probably don’t have.

Low Water Pressure Issues

Another common issue that can prevent your toilet tank from the filling is low water pressure. Several things can cause the pressure to drop, some of which are more alarming than others.

The most benign, but also the hardest to remedy on your own is a drop in pressure caused by your water supply line. If this happens, there is nothing to do but wait it out.

Alternatively, the pipes in your house may leak or be clogged by excess sediment. This usually only occurs in older pipes and can only be fixed by a professional with all the necessary tools and replacement parts.

Such a malfunction is also quite expensive, requiring things you won’t find in your local hardware store.

While you wait for the plumber to arrive and hopefully fix the leakage, make sure to cut off the water supply line leading to the toilet or the entire bathroom if a larger pipe is leaking.

Toilet Bowl Issues

It’s not just malfunctions of the tank itself that can cause it not to fill properly. Issues with the toilet bowl itself can often reflect on the tank, especially in those models where

Cracked or Damaged Toilet Bowl

While it is unlikely to cause your toilet tank won’t fill unless the toilet flapper is also used to control the water level in the tank, a damaged toilet bowl can still be a huge problem.

A cracked toilet bowl can cause the sewage water to spill all over your bathroom, spreading an unpleasant smell and forcing you to call a plumber.

Additionally, in those toilets whose tanks are directly connected to the water level of the bowl, these cracks can cause additional problems by preventing the tank from filling.

Running Toilet

If your toilet is running, it is usually caused by a leaking toilet flapper regulating the water flow between the tank and the bowl itself. The water will constantly leak into the bowl through the flap, preventing the tank from filling properly.

Additionally, you are likely to experience issues such as a puddle of water right next to your toilet and a constant drain of your water supply that will, if left unchecked, cause your water bill to skyrocket.

Luckily, this issue is relatively easy to solve. You will need to cut the toilet tank from the water supply line by shutting the valve, then flush it.

This will let the water out and allow you access to the valve that isn’t letting the flapper seal properly. Afterward, readjust or replace the malfunctioning part and close the toilet cap lid.

6 Tips on What To Do When the Toilet Tank Is Not Filling

Check the Water Supply Line

Sometimes, there is no problem with the tank, and it is simply the closed water supply line. Check the corresponding valve before you do anything else.

Is Your Tank Filling Slowly? Check the Water Pressure

Check the water pressure at the toilet tank and in other parts of the house, such as the kitchen. Sometimes it’s not your tank that is faulty, but the pressure in the pipes is lowered.

Check the Float Ball and Surrounding Toilet Parts for Any Malfunctions

A malfunction in any of the parts of the float arm mechanism will make the tank unable to fill. This system is responsible for determining the maximum water level in your tank; if it gets thrown out of balance, the tank cannot fill.

If Faced With a Leaking Pipe, Seek Professional Help

While most toilet tank issues can be resolved by using replacement parts bought in a DIY store, a leaking pipe is best handled by a plumber.

Ensure That the Overflow and Refill Tube Work as Intended

These two pipes help balance the pressure between the toilet tank and the connected pipes. If either of these pipes becomes leaky or gets clogged due to sediment, the tank fill speed will be reduced drastically, so make sure to keep them in optimal condition.

Always Keep a List of Replacement Parts on Hand

Having a set of replacement parts for your toilet and toilet tank can significantly reduce the time needed to fix any issue, whether you do it yourself or hire a certified professional.

Therefore, it is advised to keep at least some of these parts, such as a spare water valve and a floating clip in your home at all times.

Frequently Asked Questions

What to Do When Your Toilet Tank Doesn’t Fill?

There is a significant number of different issues that can stop your toilet tank from filling, and each one of them requires another solution.

Still, there are some pre-emptive measures that you can take which will help you in case of a malfunction, such as frequently checking the various parts of the tank and flushing your pipes.

First, you will need to ascertain the causes behind the tank’s failure to perform its purpose. Knowing exactly what happened will allow you to choose between fixing the problem yourself or calling a certified professional to do so.

Why is There no Water Coming Into My Toilet Tank?

No singular cause is to blame for all cases of toilet tanks not filling. Instead, such a problem can result from many different issues, such as a misaligned toilet float ball or a problem with a leaking flapper. The list goes on, with some issues being graver and more challenging to fix than others.

Why Does My Toilet Not Refill After Flushing?

Seeing that your toilet failed to refill after you flushed it can be really annoying. Thankfully, most causes leading to it are relatively benign and can be fixed in a DIY manner.

You should disconnect the tank from the water supply and lift the toilet lid to see if anything is out of place, followed by checking for leakages and other issues that may not be as noticeable at first glance.


When you have a problem with the toilet tank not filling, it is something that needs to be resolved immediately. Whether the problem is the fill valve, the overflow tube, or something else, malfunctioning toilet tanks can cause a whole host of secondary issues.

Thankfully, the majority of toilet tank problems are relatively easy to solve and, except for a pipe leakage, don’t require professional attention.

Smith Edwards

Smith Edwards is a licensed plumber and writer with over a decade of hands-on construction and home improvement experience and has been providing home improvement advice for over 12 years.

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