3 Reasons Why Your Toilet Is Slow to Fill

3 Reasons Why Your Toilet Is Slow to Fill blog banner

Does it seem like your toilet water is too slow to fill after a flush? If so, you’re not alone. A slow-filling toilet is a common problem for homeowners, but one that can be solved.

There are a few different reasons why this issue might happen. While none are especially serious or expensive to resolve, identifying the problem can help you apply the correct solution to get the toilet running optimally again as soon as possible.

In this article, we’ll explain three common causes of a slow-filling toilet, how to troubleshoot the problem, and the steps you can take to fix it.

Three Possible Reasons for a Slow-Filling Toilet

Depending on the water pressure in your home, a toilet tank will usually refill in about a minute. If you notice it’s taking a lot longer, you may have an issue that requires attention.

Here are three possible reasons your toilet water is slow to fill:

Water Supply Valve Problem

The water supply valve is the knob protruding from the wall just below your toilet tank, and it controls the water flowing into your toilet tank. If it’s partially closed or not functioning correctly, it may not be able to deliver the correct amount of water at the right speed. Yet another potential issue with the valve is a buildup of debris that can restrict water flow, inhibiting the valve’s filling speed.

Troubleshooting tip: Check the valve to make sure it’s completely open. If a fully opened valve is still not producing the right amount of water to refill the tank, contact a licensed plumber to check the valve for debris buildup.

Waterlogged Float Ball

A float ball sits on top of the water in the tank and controls the amount of incoming water in order to prevent tank overflows. If the float ball is waterlogged, it will not allow the tank to fill efficiently. As a result, it can prevent the adequate amount of water from entering the tank, or the water may refill slower than the desired rate.

Troubleshooting tip: Remove the toilet tank lid and check the water level. If it’s only partially full or the ball is not floating near the top of the tank, you may have a waterlogged float ball. The good news is that replacing the float ball is not a major plumbing feat. It’s as easy as pulling the old one off the float arm and putting the new one in its place.

It's worth noting that a float ball is old toilet technology. If this mechanism is going bad, consider replacing your inner toilet parts with modern components.

Fill Valve Tube Issues

The fill valve is attached to a vertical tube-shaped device inside the toilet tank. The fill valve’s job is to control the water level in the tank. Over time, fill valves can wear down, become clogged, or shift out of alignment. Any of these issues can prevent the toilet from filling with water properly.

Troubleshooting tip: If you’ve determined the problem is not the water supply valve or a waterlogged float ball, it’s time to take a closer look at the fill valve. Inspect the valve for signs of wear and tear or incorrect positioning inside the tank. It should typically be mounted on the left side of the tank with a tailpiece extending through the bottom of the tank, where it attaches to the supply tube and shut-off valve.

How to Fix a Slow-Filling Toilet

Now that you have a better idea of what may be causing your toilet tank to fill slowly, here are actual steps you can take to fix the problem.

1. Open the water supply valve.

Sometimes the water supply valve might be only partially open. Check the valve to make sure that it’s open all the way. If the water valve is already open, proceed to step two.

2. Adjust the fill valve.

Follow these steps to adjust the fill valve:

  • Remove the tank lid and find the fill valve — it’s usually on the left side of the tank.
  • Make sure the fill valve is securely and evenly attached to its tube.
  • For older toilets, use a flathead screwdriver to loosen the adjustment screw and raise the fill valve to let more water into the tank.
  • For newer toilets, turn the fill valve adjustment knob with your hand to let more water into the tank.
  • For all toilets, make sure the water level is about an inch below the top of the overflow tube.
  • Flush the toilet and then check to see if the tank fills at the right rate and with the right amount of water.

3. Clean the fill valve.

Notice mineral buildup or gunk on the valve? Here’s how to clean it:

  • Shut off the toilet’s water supply and remove the tank lid.
  • Remove the screws on top of the fill valve and remove the fill cap.
  • Slowly turn on the water supply, cupping your hand over the valve to prevent getting sprayed.
  • Let the water flow freely through the valve, which flushes out debris and buildup.
  • Turn the water supply off after a few seconds of letting it flow.
  • Flip the fill cap and find the washer. Remove it with a screwdriver and gently scrub away mineral buildup.
  • If you notice cracks, replace the fill valve.
  • Finally, replace the valve, secure it with the screws, and turn the water on to see if you’ve fixed the problem.

4. Fix or replace a waterlogged float ball.

  • Check to see if the float arm attached to the float ball is fixed too low in the tank. If that’s the case, bend the arm slightly upward so the ball rises higher in the tank, allowing more water to flow in.
  • If this doesn’t work and you still think the float ball is the issue, you may need to install a replacement float ball or contact your local plumber about upgrading to a newer style mechanism.

5. Fix a valve tube problem.

To fix a clogged valve tube, you must clean debris out of the tube.

  • Begin by shutting off the water supply.
  • Remove the hardware from the valve.
  • Use a slim wire or bottle brush to clean out the tube.
  • Open and shut the water supply valve a few times to flush away any remaining residue and clear all of the clogs.
  • Replace the hardware and the tube and check to see if the toilet begins to fill properly after flushing.

If the tube has holes, tears, or looks worn or damaged, install a replacement valve tube.

In general, if the issue causing your toilet to fill slowly involves a broken pipe or buildup in the pipes, we strongly recommend that you call a plumber with the experience you need to avoid further issues.

Choose Mr. Rooter® Plumbing for Toilet Repair and Replacement Services

Want to save time, avoid troubleshooting hassles, and get reliable toilet repair from the pros? The team of licensed plumbers at your local Mr. Rooter Plumbing can provide you with the toilet repair and replacement services you need. Call today or request an estimate online to get started.