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Why Is My Toilet Not Filling Up With Water? What to Do?

The average toilet tank should typically recharge three minutes after flushing. Nevertheless, there are instances where you may find it’s slow to fill or not filling at all.

So, you may be curious “Why is my toilet not filling up with water?” It can be one or more of these four reasons.

  1. Water supply issues
  2. A faulty fill valve
  3. Low float height
  4. Misaligned or worn-out flapper

Troubleshooting these potential issues should get the water back in your toilet tank. Other not-so-common causes include a damaged trip lever and a broken toilet bowl.

We’ll guide you on how to fix a slow-filling toilet tank. This will include potential problems, troubleshooting tips, and solutions.

Why Is My Toilet Not Filling Up With Water?

Maybe you’re short of time and don’t want to be bogged down by excessive explanations. If that’s the case, you can draw quick insight from our cause and solution chart in the table below.

NoPotential CauseSolution 
1Water supply issuesCheck your water source for pressure issues
Fully open the main shut-off valve
Set the pressure regulator to high
Clean the supply line for clogs
Replace pipes if broken
2Faulty fill valveAdjust the fill valve
Clean the fill valve
Replace the toilet fill valve
3Low float heightAdjust the float to a higher level
4Misaligned/worn-out flapperCheck that the flapper seals tightly against the flush drain
Replace the flapper if worn out
5Broken toilet bowlPatch with plumber’s putty or porcelain epoxy if it’s a hairline crack
Replace the toilet for larger cracks
6Damaged trip assemblyReplace the toilet handle
why toilet not filling up with water

Toilet Not Filling Up With Water: A Detailed Discussion

The following section covers the causes and solutions in detail to help you understand better.

1. Water Supply Issues

It’s very likely that there isn’t enough water pressure getting in your toilet. Basically, water pressure to the toilet should border 40 to 55 PSI. Other than broken pipes that need replacing, the primary causes of low water pressure are:

  • Shut-off valve issues
  • A clog in the hose (supply line) leading to the fill valve
  • Pressure regulator set low
  • Well failure

There’s also a likelihood of low water pressure from your municipal source.


  1. First, you want to rule out the possibility of low water pressure from the municipal source or private well. If you’re on municipal water, inquire about a water main break or hydrant flushing that could be causing a pressure drop.
  2. For a good source, check that your booster pump is running and the well hasn’t dried.
  3. Afterward, inspect the main valve leading to your house. It could be that it’s slightly closed, in which case you have to open it fully.
  4. Also, check that the water pressure regulator isn’t set too low.

This video shows how to adjust your water pressure regulator

  • Move on to the shut-off valve behind the toilet. Oftentimes, you may turn it off accidentally or leave it partially open. Check to ensure that the valve is fully open.
  • If the tank is still not filling, close the shut-off valve and disconnect the supply line at the bottom of the toilet.
  • Run the hose into a bucket and open the shut-off valve. If water doesn’t come out or very little comes out, you likely have a clog.

In that case, your first option would be to clean the supply line. You can consider a homemade cleaning solution, preferably one cup of vinegar and one cup of baking soda solution. Then follow the steps below.

  • Step 1: Disconnect the supply line from both the shut-off valve and the tank. Close one end and pour in the solution, letting it sit for an hour or two.
  • Step 2: Rinse the supply hose with hot water. If still clogged, run a plumber’s snake through the hose and rinse with a high-pressure jet.
  • Step 3: Reconnect the supply hose to the shut-off valve.  Run the hose in a bucket and open the shut-off valve.

If there’s little or no water, it may be time you replace your supply line. In rare cases, the culprit may be a supply line nut failure. The nut may develop cracks from over-tightening and excessive pull, causing leaks. Call a licensed plumber in this scenario.

2. Faulty Fill Valve

If your toilet tank is not filling up but the water is running, check the fill valve. Essentially, this is the valve that controls water flow into the tank.

Generally, there are two types of fill valves – traditional ballcocks and newer floating cup designs. And all fill valves work on the same principle. When you flush your toilet, the fill valve opens to allow water to flow from the main water supply line into the tank.

Nevertheless, the working of a fill valve may fail due to the length of time it’s been in use and debris and limescale buildup. For the record, a toilet fill valve has an average lifespan of 5 years.


If your toilet fill valve is not working, your options are to adjust, clean, or replace it. To adjust your fill valve:

  • Step 1: Locate the adjustment screw. It’s typically on top of the valve.
  • Step 2: Turn the screw clockwise to allow more water to flow into the tank.

If adjusting the fill valve doesn’t work, try cleaning it. So, how do you clean a fill valve?

  • Step 1: Close the shut-off valve and remove the top of the fill valve. You should see an opening.
  • Step 2: Hold a mug over the opening and turn on the shut-off valve. This should clear the debris.
  • Step 3: Shut off the water and replace the fill valve top. Turn the water back on.
  • Step 4: If the valve still doesn’t allow water into the tank, disconnect from the supply line and disassemble it as per the manufacturer’s instructions.
  • Step 5: Clean the parts in a solution of vinegar and baking soda to remove stubborn debris and limescale buildup.
  • Step 6: Reassemble and reconnect the fill valve. Turn the water back on.

If you’re still unlucky, disconnect and replace your old fill valve with a new one. Follow the instructions that come with the new fill valve.

The best replacement fill valves we recommend are the Fluidmaster 400A and Korky universal fill valve. They’re adjustable and last twice as long as your typical fill valves.

For a general guideline, here’s a video on how to replace a toilet fill valve for beginners.

3. Low Float Height

The float controls the water level in the tank. Essentially, it moves up and down with the water level, signaling the valve to open or close. If the float is set too low, it will stop water flow into the tank.


  1. You’ll have to adjust the float. It can be the traditional ball-and-arm float or a cylinder float. Let’s examine the procedure for each float type.
  2. For a ball-and-arm float, turn the screw on the fill valve counterclockwise. This should raise the float ball and allow water to fill the tank.

A cylinder float may have an adjustment screw or a release clip. If it’s an adjustment screw, the same rule applies.

  • Turn it counterclockwise to raise the float.
  • In the case of a release clip, pinch the clip to raise or lower the float.

4. Misaligned/Worn-Out Flapper

The flapper regulates water flow from the tank to the bowl. If it’s worn out or misaligned, it will cause water to leak from the tank to the bowl. If such is the case, the tank will not fill up. According to research, a leaking flapper can let through up to 200 gallons of water daily right under your nose.


A simple inspection and potential replacement of the flapper may resolve this issue. To diagnose whether the flapper is indeed the culprit, take these steps:

  • Step 1: Check that the chain connecting the flapper to the flush lever is properly attached. If loose, it will prevent the flapper from sealing tightly after a flush.
  • Step 2: Ensure no debris or build-up is preventing the flapper from sealing tightly against the flush valve.
  • Also, a leak may be due to a flush valve that has developed cuts, most often from the abrasive effects of grit. This will cause the flapper to lose its seal.

If neither issues are present, replace the flapper following these steps:

  • Step 1: Close the shut-off valve and flush the tank. Use a sponge to remove any remaining water.
  • Step 2: Disconnect the chain to the flapper and loosen the plastic tab securing the flapper to the overflow tube. Now remove the old flapper.
  • Step 3: Position your new flapper in the same position as your old one by aligning it with the valve seat. Secure it in place by hooking the flapper arms to pins on the overflow tube.
  • Step 4:  Adjust your flapper chain. Primarily, you want it tight enough to lift the flapper when flushing your toilet. But it shouldn’t be so loose that it leaves the flapper open.
  • Step 5: Turn on the water to test your new flapper.


Let’s address common questions and concerns you may have about the topic.

Q: Why is my toilet bowl not filling all the way?

We can attribute this to a damaged or incorrectly positioned fill tube within the tank. The fill tube is what controls the amount of water entering your toilet bowl.

Q: How do you fix a shut-off valve that is stuck closed?

Lubricate it with WD-40 spray at the joint between the valve stem and body, leaving it for 30 minutes. Twist the shut-off valve in quarter turns between open and closed positions until you get no resistance. Then fully open the valve.

Q: Are there best practices to minimize the risk of toilet tanks not filling quickly?

Regularly clean the fill valve and flapper to remove dirt, mineral buildup, or corrosion. Also, avoid using harsh chemicals like bleach and drain cleaners that can damage your toilet’s inner workings.


Your toilet tank not filling up may be due to a faulty fill valve, a low float height, a faulty flapper, or a clogged supply line. You should be able to fix all these issues through our simple DIY repairs.

Nevertheless, if the issue persists despite your attempts, it may indicate a serious underlying issue. This will call for the expertise of a professional plumber to address the root cause of the problem. Be that as it may, it’s highly unlikely that our DIY solutions will fail, not unless you’re not confident in plumbing works.