8 Reasons Behind Your Toilet Tank Not Filling & What to Do


Is your toilet tank not filling properly? If so, you are undoubtedly facing a major inconvenience. While such problems occur quite often, you need to resolve them as soon as possible. Not all toilet tank issues require you to call for a professional plumber — sometimes, you can simply fix them yourself.

In this article, you will find the top eight reasons for a toilet tank not filling and what you need to do for each of them. But before that, let’s take a look at exactly how a toilet works. You need to know the basics in order to successfully determine the cause of the problem at hand.

How Does a Toilet Work?

Toilet tanks are designed to automatically fill up with water each time you flush. Typically, it takes around ten seconds for a tank to fill completely and the water level should be just below the overflow tube. The tank has a lot of moving parts that make it work — if even a single one malfunctions, that might cause the entire tank to stop working properly.

When you flush, a handle arm pulls up a chain connected to the flapper and flush valve inside the tank. As a result, all water contained in the tank is dumped into the toilet bowl. Once the tank is completely emptied, the flapper once again covers the drain hole, and water starts coming into the tank to refill it. A mechanism called a float ball is responsible for determining when the tank is refilled.

8 Reasons for a Toilet Tank Not Filling

Since the toilet tank has so many different moving parts, the odds of one of them going faulty are quite high. If you are experiencing issues with your toilet tank, first you need to determine what causes them. Below, you will find the eight most common reasons for your toilet tank not filling with water.

While some of them are not complex and can be fixed with relative ease, others require you to seek professional help.

Before starting to analyze the problem, make sure you familiarize yourself with the different parts of a toilet tank. Look up a diagram online — it will be extremely helpful as you go down the list below.

#1. Misadjusted Fill Valve

The fill valve is an assembly of tubes that regulates when a toilet tank fills or stops filling. Depending on the age and type of your toilet tank, the fill valve might look significantly different. However, if it is not properly adjusted, it might cause your tank to not fill properly. Locate it and see if there is any debris or other obstructions within the tube itself.

You should also check if the fill valve is properly installed and without any visible cracks. There should be no water leaking from it — if there is, you will have to replace it with a new one. If the fill valve is intact, the issue might occur because it is too tight and does not let the tank fill properly.

Check if your fill valve has a screw on its top — that regulates the volume of water that is let in. If you turn it clockwise, you will allow for more water to come in when the tank is filling. Sometimes there is a clip on the side of the fill valve instead of a screw. Regulate the volume of water by sliding it up for more and down for less.

#2. Low Water Pressure

If your toilet tank is filling so slowly that it feels like it is not filling at all, you might have a problem with water pressure. Indeed, low pressure can be a huge issue not only for your toilet, but for your shower, sink, and other appliances as well. Low water pressure is usually the result of a malfunctioning water pump. Also, if you live on the top floors of a higher building, you might be experiencing issues with water pressure as well.

Unfortunately, you cannot take care of this problem by yourself. The best solution is to install a booster pump, which is a task only a professional plumber can handle.

#3. Broken Toilet Bowl

A cracked or damaged toilet bowl might result in water leaks, which will prevent the toilet tank from filling properly. Sometimes, the cracks are small and located at the back of the toilet — as a result, you will not be able to see the water pooling on the floor. If you suspect that your toilet bowl is cracked, make sure you do not use the toilet until the issue is fixed. It might collapse under you and flood your bathroom.

A broken toilet bowl needs to be replaced with a new one as soon as possible. Before you contact a professional, make sure you stop the supply of water to the toilet. You can do that either from the valve that connects the toilet itself to the plumbing, or the main valve for the bathroom as a whole. Keep in mind that any damage to the toilet bowl can get worse if not addressed on time, so do not delay the replacement.

#4. Worn-Out Flapper Valve

The flapper valve is responsible for keeping the tank water from emptying into the toilet when it’s not being flushed. It is a small rubber valve located at the very bottom of the toilet tank. If it is not working properly, it will affect how your tank is filling and might even result in the toilet constantly running. There are a few things that can go wrong with a flapper valve — let’s take a look at the most common scenarios.

The flapper valve is usually held in place by a chain. However, if that chain is misplaced and caught up under the valve, it will prevent it from sealing properly. Also, the chain can get worn out or damaged — in this case, you have to replace it with a new one.

In some toilet tanks, the chain is simply too long and cannot properly hold the flapper valve in place. In this situation, you need to shorten it or replace it with a smaller chain.

When it comes to the flapper valve itself, it can get worn out, just like all other parts inside of the toilet tank. If the flapper valve is hardened, it will not be able to seal properly, resulting in your toilet tank malfunctioning.

The only thing you can do in such cases is to replace it with a new one. While it is not a difficult task, you might want to leave it to a professional — it all depends on your confidence level when it comes to plumbing repairs.

#5. Damaged Trip Lever

Another common cause of a toilet tank not filling is a faulty trip lever assembly. In most such cases, the part that connects to the handle has disconnected due to corrosion or some other damage. You can locate the issue by removing the cover of your toilet tank and inspecting the trip lever assembly. The problem can be easily fixed by getting a new part and replacing it.

It is always a good idea to take a picture of the issue and show it to the staff of your local hardware store. They will usually know exactly what you need in order to fix the issue. If you do not feel comfortable doing the replacement yourself, you can always call a plumber. A professional will have the parts and tools needed to properly replace your damaged trip lever.

#6. Broken or Misadjusted Float Arm or Ball

In many toilet tanks, the fill valve is controlled by a float arm and ball system. If those components are damaged or worn out, it will probably result in your toilet tank not filling. While the setup of the float arm and ball system is fairly simple, there are multiple ways in which problems can occur. Also, you can take care of almost all related problems yourself, since there are float arm and ball kits in most hardware stores.

Sometimes, the float arm is not adjusted properly and does not allow water to come into the tank. You can easily fix that by simply bending the arm upward, which will raise the ball to a new level. Some float arm and ball systems have screws that you need to tinker with in order to set the height. Feel free to test different positions until you find the one that works best.

If either the arm or ball is worn out or broken, you just need to replace them. As previously mentioned, you can get replacement parts at any hardware store. The float arm and ball systems are generally easy to install. However, if you are not feeling comfortable doing it yourself, seek the services of a professional plumber.

#7. Damaged Overflow Tube

The overflow tube is a large tube that transports excess water in the toilet tank to the toilet bowl, in order to avoid overflowing. It is located right in the middle of the toilet tank and is essentially a part of the flush valve. If the overflow tube is damaged, it will result in your toilet tank not filling while water is running into the toilet non-stop. If this is the issue, the only option you have is to replace it with a new one.

Fortunately, you can take care of this problem by yourself with relative ease. Just pull out the overflow tube and insert the replacement in its place. Of course, you need to make sure the new tube is the same size as the old one. Alternatively, you can just replace the entire flush valve mechanism.

#8. Problem with the Water Supply

If everything seems okay with your toilet tank but it is not filling as it should, you might have a larger water supply problem on your hands. The first thing you should do is check the main valve that connects the water supply to your toilet. Is it in the open position?

You will be amazed how often this ends up being the cause of a toilet tank not filling. The valve might have been accidentally closed by workers or children. If the valve is open, then the issue might be more general.

Check if your bathroom sink works properly. If there is no water there as well, the overall water supply to your building might have been disrupted. Check with your neighbors and local water authorities to see if there is any water that actually enters the building.

If your home is receiving water, but it does not reach your bathroom, this means that you have a blockage or massive leak in your internal plumbing system.

Dealing with such complex plumbing issues should only be handled by licensed professionals. If this is the cause of your toilet tank not filling, get in touch with a local plumbing company. The professionals will know how to proceed and resolve the problem.


So, there you have it — the eight most common reasons behind a toilet tank not filling and what you can do about each of them. Even though some of those issues seem easy to take care of by yourself, make sure you do your research.

You do not want to end up making the problem worse or accidentally flooding your entire bathroom. If you are not comfortable with doing plumbing repairs, just call a professional and let them take care of the job for you.


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