How to Fix Toilet Tank Not Filling Up – 9 Common Causes and Solutions

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When your bathroom toilet works properly, you barely even think about it. But when issues with your toilet arise, it can seem like the biggest inconvenience in the world. 

One of the most common issues? The toilet tank not filling. 

Here’s what happens: you flush the toilet, watch the water go down, and wait for the water to fill back up. But it doesn’t, and you’re left wondering why. 

We’ve looked into the most common reasons why water is not filling up in your toilet tank, and we’ve researched the best ways to fix it.

How to Fix a Toilet Tank Not Filling With Water

If you notice your toilet tank not filling with water, the first thing that you’ll need to do is narrow down the root cause of the issue. 

There could be a problem with the water pressure, or perhaps the toilet fill valve has broken. 

Or, the issue could be a bit more complicated — such as problems within your sewer line, or a damaged toilet bowl that needs to be replaced. Whatever the issue, it’s best to tend to it as soon as possible to prevent a potentially bigger problem with your plumbing.

Here are the 9 most common reasons for a toilet tank not filling, and how to fix them yourself.

1. Adjust the Float Ball

Most toilets contain a toilet float ball (aka a “ball float”) which works to regulate water inside of the tank. This ball is attached to a 10–12 inch metal rod that’s connected to the tank’s fill valve. 

(It’s important to note that some newer toilet models may not have this traditional toilet ball, though most do.)

After some time, the float ball’s arm can drop from its original position or become worn out, which may cause the toilet to leak or prevent it from filling properly. You can adjust the ball manually if it’s fallen from its position. 

To do this, first remove the toilet lid. Next, grab the float arm and bend it upwards about 1/8 of an inch. If your float arm has a screw attachment, you can also manipulate this part as well. If you need more instructions, check out our step by step guide to adjusting a toilet float.

After doing so, flush the toilet to see if the tank fills properly. If it’s still low, adjust the float arm until the water fills to the right level.

2. Adjust the Fill Valve

This part is also known as the “flush valve” and, more often than not, the cause of a slow filling toilet tank.

A fill valve is a tube assembly located inside the tank, and is responsible for refilling it after the toilet is flushed. 

The actual setup of this assembly may vary by brand, but you should still be able to adjust it rather easily. 

If you have a fill valve that has a screw on the top, you can typically adjust it with a flat head screwdriver. To do so, turn the valve clockwise — this’ll allow more water inside the tank. 

And, of course, just turn the valve counter-clockwise if you overdo it. Then, flush the toilet to check the new water level and keep adjusting if needed. 

If you have the type of fill valve with a screw that has a clip on the side, use your index finger and thumb to slide it up to increase the water level (to decrease the water level, just move it down). You may need to play with it a bit to get the level just right.

3. Replace the Trip Assembly

Sometimes the trip assembly inside the toilet can fail, causing the toilet to fill up with less water than it should — this is an L-shaped metal or plastic lever that’s connected to the toilet handle. 

When you press the toilet flush handle, the lever lifts to open up the slapper inside the tank, thus allowing the water to drain out and fresh water to enter the bowl. 

Depending on the make and model of your toilet, the lever may also come attached with its own housing. 

With this in mind, if the lever becomes faulty or breaks, you’ll need to replace it with a new one. And, if it’s connected to an assembly, you’ll also need to purchase the entire repair kit. 

Still, it’s an easy and inexpensive fix.

4. Replace the Toilet Flapper

The toilet flapper is probably the most recognizable component inside the tank. 

This valve is typically made of rubber and is usually about 4–5 inches in diameter. It’s attached to the lift chain and drains the tank and bowl when the toilet is flushed. 

However, as this valve ages, it can become worn and may eventually harden. If it does, it’ll have to be replaced. Follow our tutorial on removing a hard flapper, before replacing with a new one. If you’re a handy person, this’ll be a rather easy DIY project. You can purchase a new flapper at your local hardware store. 

These valves are also usually universal, meaning that most will fit in various toilet brands and models. 

Need a visual? Check out this video to see how to replace it yourself:

5. Check the Water Pressure

Though this may seem like an obvious thing to check, it can be easy to overlook. If you suspect that low water pressure may be the issue with your toilet, you’ll need to do a bit of troubleshooting. 

Start by turning on the water in the bathroom sink. If the water doesn’t work, try the other sinks in your home. If none of them work, chances are you have a water supply line issue and you’ll need to reach out to your local water supply company. 

However, if it’s just the toilet, check the water valve located underneath to make sure that it isn’t in the shut-off position. Sometimes pets and small children can accidentally close the valve, causing the toilet’s water levels to change. 

To increase the water pressure, grab the valve with your hand or an Allen wrench (if it’s too stiff) and slowly turn it counter-clockwise. If the valve won’t turn, this means that it’s already open to the max. 

Turn it only about an eighth of an inch at a time. After each turn, flush the toilet and check to see if the water level is back to what it should be.

6. Replace the Overflow Tube

Sometimes the overflow tube inside the toilet’s tank can also cause water level issues. As a result, it’ll prevent water from filling up the toilet to the right level — or it can cause the toilet to fill up with too much water. 

When troubleshooting the cause of your water level issue, check the overflow tube to see if it is worn or damaged in any way. If so, you’ll need to replace it. 

To do this, start by turning off the water supply line at the water valve. Next, remove the washer, the plastic outlet ring, and the screws (there are usually four) that hold it in place. 

Then, pull the tube out from its position. Install the new tube, and be sure to fasten the screws with a screwdriver. Next, turn the water back on and flush the toilet to check the water level.

Have a look at this video to see exactly how it’s done:

7. Replace the Fill Valve

Sometimes the fill valve needs more than just a simple adjustment. In some cases, the valve is just too old or worn out to function properly. 

When this is the issue, the toilet will do one of two things: It will either continue to run, wasting gallons of water, or not fill properly. 

Fill valves are inexpensive — they can be purchased for around $10 — and you can replace one by yourself in about 15 minutes. 

Start by draining the toilet tank of as much water as you can — to do this, hold down the flush lever until the water gets as low as possible. Next, turn off the water at the supply valve. Then, remove the clip from the top of the fill valve and pull it out of its position. 

Place the new valve in its place and secure it using the included hardware. Once everything is in position, open up the toilet valve and flush it to see if the bowl and tank fill to the correct level. 

8. Check for a Cracked Toilet Bowl

While toilet cracks are the least common reason for water level issues, they can still happen and prevent your toilet from filling sufficiently. 

If all other components seem to be functioning properly and there is no issue with the water supply, this may very well be the culprit. 

To check for this, closely inspect your toilet, starting at the bowl. Do you notice any cracks near the floor or around the top? If you do, turn off the water supply at the valve asap. 

Next, tape a “do not use” sign to the toilet and refrain from using it until it’s replaced. 

A cracked toilet can easily collapse when used. And, as a result, it can actually flood your bathroom. Scary right? This definitely isn’t ideal, and can create a home-reno emergency in a heartbeat. 

If the bowl is cracked it’s best to replace the toilet as soon as possible.

9. Check for a Blocked Sewer Vent Line

Sometimes clogs in your sewer vent line can cause low fill levels in your toilet. If you notice any foul-smelling gases emitting from your toilet or gurgling noises coming from the bowl, this may be the issue. 

These clogs can be caused by a number of things, including non-biodegradable items being flushed down the toilet to leaves and carcasses from local wildlife getting caught. If this is the culprit, it’s best to clear the vent line of the blockage. 

You can attempt to do this yourself if you’re familiar with your home’s sewer system. However, it may be best to contact a licensed professional plumber who can use professional equipment to clear the line safely and quickly.


When a toilet tank is not filling up with water after flushing, there’s often an issue with an internal component side the tank. However, plumbing and sewer vent line issues can also be to blame. 

To troubleshoot the issue, start by inspecting the inner workings of the toilet. Many times, you’ll find the solution a simple fix. We hope these 9 common causes and DIY fixes has solved your problem and your toilet tank is now working again.

If not, you may need to contact a plumber for assistance. Good luck!