Why Your Toilet Tank Is Not Filling Up With Water

The bathroom toilet is one of the most used things in your home, yet it’s not commonly thought about when doing routine maintenance. When the water in the toilet tank no longer fills up, it can be quite an annoying issue to encounter. This can often result from a combination of multiple different things, especially if you haven’t been keeping up with the maintenance of it. 

Your toilet tank is designed to fill up with water immediately after you flush. If the toilet tank is not filling up, then you have a plumbing issue on your hands. Before you call a plumber to come to take a look at it, there are some things you should check out and fix beforehand. Here we cover some of the main reasons why your toilet might not be filling up with water and ways to fix it.

toilet tank diagram

Toilet Float Not Adjusted At Correct Levels

The toilet float connects to the toilet fill valve and controls the level of water in your toilet bowl. Setting the toilet float ball low reduces the water that enters the tank and vice-versa.

You might need to adjust the float valve to increase the water level to acceptable levels. Here are steps on how to tweak the float for greater water flow:

  • First, you need to turn the shut-off valve clockwise to stop water from flowing into the toilet bowl. Then flush out any water left in the toilet and detach the toilet tank lid.
  • Next comes the actual float change. How you do that depends on what type of float valve you have — whether its a float cup or float ball. Most modern toilets use a float cup, which is smaller than the float balls used in older models.f
  • If your toilet uses a float cup, find the screw between the fill valve and float arm. Turn this screw clockwise with a flathead screwdriver until the water reaches 1/2 - ⅓ below the overflow tube. If your toilet uses a float ball, find the plastic screw connected to the float arm and turn the screw.
  • You want to be careful when you adjust the float valve. Turn the screws slowly and ensure that the water doesn't overflow. It’s often best to let the water reach ½ inches below the overflow tube.

Faulty Toilet Flapper

The toilet flapper blocks the opening to the flush valve so that the toilet tank can fill up for the next flush. When you flush, what happens is that the worn out flapper opens to let water through before it closes again.

A lift chain links the flapper to the toilet flush lever. Pushing down the handle unseats the flapper, and releasing it returns it to its position.

Ensure the chain has some slack, around ½ inches. A tight chain can unseat the flapper, which means your toilet tank won't fill up with water. A short chain can also result in the water not flushing all the way down.

This problem also occurs when the lift chain hangs loosely or hooks on another part of the tank. The flapper cannot block the cavity, so the toilet won't refill properly after you flush.

Debris may also be the reason your toilet won't fill up. Occasionally, minerals and debris will build up around the toilet flapper, preventing it from sealing the flush valve opening. If your toilet tank won't fill up because of this issue, clean the toilet flapper and remove all minerals and debris deposits.

Your last resort is to replace the worn out flapper, especially if the other steps don’t work. Inspect the flapper for signs of wear or warping to know if it needs replacement. Here is a handy guide for replacing the toilet flapper:

  • Locate the shut-off valve and turn it clockwise to restrict the water supply to the toilet. Afterward, flush out water from the toilet and remove the toilet lid.
  • The next step requires unhooking the lift chain from the toilet handle and detach the flapper from the overflow tube. Now, you can clean the flush opening and remove any dirt preventing the flapper from seating properly.
  • Install the flapper and secure it to the overflow tube. You'll still need to hook the lift chain to the handle for it to work correctly.
  • Rotate the shut-off valve anti-clockwise to get water into the toilet tank. Confirm that the tank refills quickly before returning the lid to its position.
toilet tank not filling

Low Water Pressure 

A common reason many toilets don’t fill up quickly is due to low water pressure. This problem is usually the combination of different factors, such as mineral buildups, leaks, or poor water supply.

Before anything else, find out if the low water pressure is limited to your bathroom or other places like your bathroom sink and kitchen. If this issue affects only your toilet, the water supply line could be clogged leading to an issue in the flush cycle. Make sure to check if things like kitchen faucet work or other places around the home. If that’s the case, you might need something like a water pressure booster to increase the water pressure around the entire house.

If it’s limited to the toilet, uninstall the pipe and remove any material blocking the flow of water. That should solve the problem, and if it doesn't fix it, contact your plumber to check the main pipes that supply your toilet with water.

Overflow Tube Needs To Be Replaced

The overflow tube transfers excess water from the toilet tank into the toilet tube to prevent the former from overflowing.

In some cases, a toilet not filling up problem can be caused by a faulty overflow tube. The tube can crack, which means water continually leaves the tank even if the latter isn't full.

It doesn't take a lot to install a new overflow tube. Simply remove the old cracked overflow tube from the flush valve base and insert the replacement—just make sure you get the correct size.

Cracked Toilet Bowl

A cracked toilet bowl can be why the water in your toilet tank won't rise. Water will leak out of the toilet, making your tank look empty even when it runs perfectly.

Although broken toilet bowls are rare, you want to rule out all possibilities. Look at the bowl and check for any holes and cracks. And if you notice the toilet bowl is cracked anywhere, buy a replacement. This issue can also cause low water in the bowl itself.

If your toilet bowl is cracked, you will want to replace it whether your toilet doesn’t fill up or not. A crack often signals that it’s met its end, and you don’t want things to break down when someone uses the bathroom. 

Broken Fill Valves

The toilet fill valve connects to the water supply line, toilet float, and overflow tube. The fill valve sends fresh water into the tank when you flush, so there's always water for flushing.

A broken fill valve can cause a slow-filling toilet tank, so you'll want to replace the fill valve. This is a common problem that many homeowners face, but it's luckily an easy problem to fix. Here is how to troubleshoot a faulty fill valve:

  • For starters, you need to stop the inflow of water into the toilet and flush out the bowl. Next, turn the fill valve cap counterclockwise to remove it. Check the valve seat for debris and clean it with water.
  • You also want to confirm if the fill valve is connected to the overflow tube. When the toilet fill valve disconnects from the overflow tube, the water supply to the tank will reduce. Once you link both parts, your toilet tank should start filling up normally.
  • If the fill valves are beyond repair, buy a replacement online or at your local hardware store. They’re quite easy to find, so you’ll have no trouble finding a cheap fill valve that suits your needs.

Shut-off Valve Needs Fixing

This is one of the most common issues that gets looked over by most people. Before you start looking for complex issues, make sure that the shut-off valve is open.

To find the shut-off valve, check the toilet's rear area. Small toilets might have this located in other places. Once you locate the valve, rotate it counterclockwise to open the water supply line to the toilet tank. If your shut-off valve has a push/pull mechanism, you'll need to press the valve handle to get water flowing through the toilet again.

If your toilet fills up slowly or won't fill up at all, make sure that the aforementioned factors aren't causing the problems. Most require basic DIY fixes you can perform without needing to hire a pro. In the unlikely case that these fixes don't work for you, you will need to call a professional plumber to come and take a look at your issue.

About the author 

Nelson Salas is the owner of Amigo Rooter & Plumbing in Goodyear, Arizona, a suburb of Phoenix. He has worked as a master plumber in Arizona and Texas for over 14 years.

Leave a Reply

Your email address will not be published. Required fields are marked

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}