4 Reasons Your Toilet Takes A Long Time To Fill | How To Fix

Does it seem to take a long time for your toilet to fill back up after you flush it? While the issue isn’t an emergency, it can be frustrating when the commode doesn’t work as efficiently as it should. 

This is a common problem that many people face. Luckily, the fix is relatively easy and inexpensive, so keep reading to find out how to troubleshoot the problem and fix it accordingly.

Reasons for A Slow Filling Toilet Tank

The reason your toilet is filling slowly could be because of several different reasons. Most have to do with normal wear and tear, so it isn’t much you can do to prevent them from happening, but rest assured, they are simple to fix. Let’s take a look at the causes of a slow-filling toilet, so you can identify the problem and get it fixed quickly. 

1. Issue with Water Supply Valve

The water supply valve is the knob that sits behind/below your toilet that allows water to flow into the tank. This knob can be turned on and off to regulate the flow of water into the toilet.

To allow the right amount of water to flow into the tank when the toilet is flushed, the water supply valve must be open all the way. Sometimes, however, this knob can inadvertently get turned the opposite way, restricting the flow of water into the tank, or stopping it altogether. 

If it seems like it is taking forever for your toilet to fill after flushing, check that the water supply valve is open all the way. If it is and your toilet is still filling slowly, you may need to call in a plumber as the water fill valve may be blocked by mineral deposits (hard water buildup) or other debris. 

2. Tank Float Ball Has Water In It

Older toilet models use a float arm and a float ball to regulate the water level inside the toilet tank. If this ball becomes waterlogged, it won’t be able to accurately measure the amount of water in the tank. Sometimes, a waterlogged float ball will only allow the tank to fill partially, and sometimes, it will cause the water to fill slowly after flushing. 

To find out if this is the reason for your slowly filling toilet, take the cover off the tank and observe the water level. If it isn’t as high as it should be, check to see if the float ball is in the right position. If it isn’t sitting at the top of the water, it is likely cracked and filled with water. 

To fix this problem, simply pull the damaged float ball off the float arm and replace it with a new one. 

*Note: The float arm/float ball mechanism is old-school toilet technology. Today’s models don’t have these parts. If your toilet still has a float arm and float ball, consider replacing them with modern toilet technology that eliminates this potential issue. 

3. Swollen Fill Valve Seal

Modern toilets have fill valves rather than float balls. This technology isn’t without its problems, though. The fill valve sits in the toilet tank and regulates the water level inside. 

There is a rubber seal in the fill valve that can become swollen over time due to chlorine in the water or simple wear and tear. When this happens, water can flow more slowly into the toilet. Sometimes, debris can build up around the seal, causing water to flow more slowly as well. 

The easiest way to fix this issue is to head to your local hardware store and purchase a new fill valve seal and replace it yourself. The process is relatively simple, and I will cover it step-by-step later in this article. 

4. Faulty or Blocked Fill Valve

The fill valve in your toilet is attached to a vertical tube that helps measure the water level inside the tank. Over time, these parts can wear out, become blocked, or shift out of alignment, any of which can cause your toilet to fill more slowly than normal. 

If you have determined that none of the other causes listed above is the issue with your slow-filling toilet, the problem could be with the fill valve and/or the fill tube. The fill valve and tube are located on the left side of the toilet tank with the bottom of the tube passing through the bottom of the tank to attach to the water supply valve outside the tank. 

How Can I Fix A Slow-Filling Toilet?

Now that you know the reason your toilet is filling slowly, it is time to fix it. Below, I will give you step-by-step guidance to fix these common slow-filling toilet issues. 

*Note: For all these fixes, remember to close the water supply valve completely before beginning the repair. 

Replace Fill Valve Seal

  • 1. Purchase a replacement fill valve seal from Amazon.com
  • 2. Remove the tank cover and locate the fill valve on the left side of the tank. 
  • 3. Disassemble the fill valve by twisting the top of the tube to remove it from the bottom. 
  • 4. Identify the rubber seal and pry it out of the tube taking care not to damage the pin that is in the center. 
  • 5. Install the new seal and twist the tube back together. 
  • 6. Turn the water back on and test. 
toilet fill valve - Toilet Takes A Long Time To Fill

How To Replace Toilet Fill Valve Unit

If you can’t diagnose the problem, your best bet is to simply replace the entire fill valve unit completely. This will likely fix any issues with a faulty valve seal, blockage, or misalignment within the unit. If you aren’t comfortable with making the repairs yourself, call a reputable plumber. If you fancy yourself a capable do-it-yourselfer, proceed with the replacement following the steps below. 

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  • 1. Ensure that the water is shut off to the toilet and put a towel down under the water supply valve. You may also want to put a small bucket under the water supply valve to catch any water that remains inside the tank. 
  • 2. Flush the toilet. This will remove the water in the tank. 
  • 3. Detach the water supply line.
  • 4. Remove the fill valve from the tank.
  • 5. Install the new fill valve in the tank, you can purchase a replacement unit here at Amazon.com
  • 6. Reconnect the water supply line. 
  • 7. Turn the water back on. Check for leaks.
  • 8. Observe the water level in the tank. It should stop one inch below the top of the fill tube. Adjust the level accordingly. 

Toilet Bowl Filling Slowly

By now, you should have a good idea of why your toilet takes a long time to fill. The issue is likely caused by a worn or damaged ball float or fill valve. While the inner workings of a toilet are relatively simple, it can still be challenging to identify the cause of an issue like a slowly filling toilet. Let’s run down some of the causes again. 

  • 1. Check the water fill valve. Is it open all the way? If not, turn the knob counterclockwise until you can’t turn it anymore. 
  • 2. If your toilet has a float arm and ball float, check that the ball float isn’t cracked or otherwise damaged. If it is, it probably has water inside that keeps it from rising and measuring the water level inside the tank properly. Replace the float. 
  • 3. If your toilet has a fill valve instead of a ball float, the rubber seal inside could be swollen, which can impede water flow. The fill tube may be misaligned as well, which can cause the water in your toilet to fill more slowly than it should. Replace the seal or the entire fill valve unit to fix the issue. 

Again, while these fixes are easy enough for the average homeowner to address themselves, if you don’t feel comfortable making the repairs yourself, don’t hesitate to call a reputable plumber in your area. There is no reason to stress over a slow-filling toilet issue. 

You may also be interested in 5 Reasons Your Toilet Is Flushing Slowly

Verdict: Toilet Takes A Long Time To Fill

When a toilet takes a long time to fill, it is often a fill valve or ball float issue. Hopefully, this article has helped you figure out why your toilet takes a long time to fill. Whether it is a partially closed water supply valve, an issue with the fill valve, or a worn float arm and ballcock, you are now informed and prepared to fix the issue yourself if you want. 

Most hardware stores and big-box home improvement stores carry the parts you will need to fix your slow-filling toilet issues, and while the cost will vary from one retailer to the next, you should find the parts to be relatively inexpensive and easy to find. 

If your toilet takes a long time to fill, don’t worry because the solution is easier than you think. With the fixes outlined above, your toilet will be running efficiently once again before you know it.

Plumber and HVAC Technician | Website | + posts

As a retired Master Plumber Jamie has over 30 years of hands-on experience, making his plumbing knowledge second to none. He has also worked on both residential and commercial HVAC installation and repair projects.