How To Fix A Slow Filling Toilet Tank

slow filling toilet

Are you having problems with your slow filling toilet or a toilet that won’t refill at all? This is a very common problem that plumbers come in to repair. There are a few reasons why it happens and a lot are daily easy to fix and inexpensive, but regardless they are best resolved by a professional plumber. That way they can identify the issue quickly and fix them before they turn into a bigger problem. Here is a look at some of the common reasons for toilets not filling properly and how a professional might go about fixing it.

Three common reasons for slow filling toilet

While how quickly a toilet tank refills varies depending on the home’s water pressure, on average it takes about a minute. If you notice there is a big difference in that speed and it is a lot slower there are three common reasons for that.

1. A problem with the water supply valve

The knob that sticks out from the wall just under the tank of the toilet is the water supply valve. This controls the water that flows to the tank. If it is not working or there is a problem with it then it does not allow the right amount of water at the speed it used to. The build-up of dirt and debris in the valve can also restrict the flow of water and slow the speed down.

2. A float ball that is waterlogged

The float ball is what sits on the surface of the water and controls how much water comes in. If you notice the toilet not refilling properly it could be a waterlogged float ball.

3. Problems with the fill valve tube

Another common cause is an issue with the fill valve. It is attached to a tube-shaped vertical part inside the tank. It controls the level of water and over time they wear down, shift out of place or get clogged up and that can cause issues with the re-fill.

Fixing a slow filling toilet

Steps to finding and fixing the problem of toilet tank not refilling properly that a plumber will follow.

  1. Opening the water supply valve – If it is only slightly turned opening it all the way can help.
  2. Making adjustments to the fill valve – To do this the rank lid needs removing first to find the valve on the side of the tank. Ensure it is secure and attached to the tube. With toilets that are older, you can use a screwdriver to loosen them and raise them to let in more water. For newer types, you just need to use your hand and turn the adjustment knob. When the toilet cistern is not filling up make sure the level of water in the tank is around 2 cm lowers than the overflow tube. Flush and check it now refills at a better rate. Check if the toilet cistern is in need of replacing as well.
  3. Cleaning the fill valve – If you can see gunk and mineral buildup in the valve it needs cleaning as that can cause the problem that the toilet tank won’t fill with water. Turn off the water supply and take off the tank lid. Unscrew the screws on the fill valve and take off the cap. Turn on the water supply slowly with a hand over the valve so you do not get wet. Let the water fun so it flushes out any buildup. After a few seconds turn it back off. Get the washer from the fill cap and clean it off. If there are cracks replace them. Replace it all as it was and turn on the water and check it’s fixed.
  4. Replacing or fixing a flat ball that is waterlogged – Look at the float arm and float ball in the tank if your toilet won’t refill. Bend the arm to have the ball raise high in the toilet tank so more water can come in. You can replace the float ball or your plumber can upgrade to a newer type.
  5. Repairing issues with the valve tube – If the toilet not refilling is because of a clogged valve tube then this needs cleaning. Shut off the water first and then remove the hardware. With a bottle brush or similar small wire brush clean the tube. Open and close the water valve several times to flush the dirt away. Check to see if the toilet now refills better.

Bonus Read: Is Your Toilet Not Flushing? Here Is The Fix!


There are a lot of reasons that may cause a slow filling toilet and simple checks and fixes could help it get back to normal. But if you’ve done all the steps we’ve given and you’re still having that issues, it is high time for you to contact the best plumbers near you!

Here at Best Plumbers Club, our network of verified plumbers can help you with all your toilet plumbing issues. They are backed up with experience, checked and verified by a Level 5 Google local guide and offers a lifetime workmanship guarantee. So all you need to do is get in touch with us and we will do the rest for you!