Toilet Tank Not Filling: Why & How to Fix It Fast

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Hubert Miles

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Residential and commercial toilets are one of the most straightforward and uncomplicated plumbing fixtures on your property. However, despite being easy to use and very low maintenance, toilets have their fair share of potential issues. Aside from clogs, having a toilet that won’t fill up is one of the most common problems in the bathroom. 

Several different things could be causing your toilet tank not to fill with water. While the most common reason for a toilet not filling is a busted fill valve, there could be many things happening. You could have a faulty flapper, water supply line, float, or even a leak. 

If your toilet tank won’t fill up with water, there’s a very good chance that it won’t flush. You won’t be able to use a toilet that doesn’t flush, which means it’s crucial to find a remedy. This article will look at all the possible reasons that your toilet isn’t filling and what to do about them. Let’s get flushing! 

How Does a Toilet Work? 

To better understand each of the problems associated with a toilet that won’t fill, you should first understand how a toilet works. Once you know the purpose of each component, it will make sense why any one of them can cause a problem. 

  1. You push the toilet flush lever or handle to initiate the flushing process. 
  2. The handle you push has an arm inside the toilet tank connected to a lift chain. 
  3. As you push the toilet handle down on the outside, the arm on the inside with the chain attached to it lifts. 
  4. The other end of the chain gets connected to a flapper. As the chain raises, it lifts the flapper to let water flow down the flush valve and into the toilet bowl. 
  5. When water has gone from the tank to the bowl, the flapper sits back down as the toilet handle returns to its resting position. 
  6. The flapper forms a perfect seal around the flush valve and keeps water flowing back into the tank from draining into the toilet bowl. 
  7. A fill valve in the toilet tank activates and allows water to flow from the supply line back into the tank. 
  8. Water flows from the base of the valve and fills the tank by entering through the refill tube. 
  9. There’s an overflow tube that the fill valve gets attached to that prevents water from overfilling in your toilet tank. 
  10. Your tank also gets equipped with a toilet float that rises with the water in it and signals the fill valve when the tank is full, and it’s time to shut off the water supply. 
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Top Reasons Why My Toilet Won’t Fill and What to Do 

Now that you know that each of a toilet’s components plays a vital role, let’s look at what can happen to them which causes your toilet not to fill. 

Water Supply Line Issues 

One of the most apparent possible problems is that you have a problem with your water supply line. Your supply line is connected to the back of your toilet, usually somewhere close to the ground. If you recently had your toilet worked on, it’s possible that you or your plumbing professional forgot to turn the water back on after you completed the repairs. 

It’s also possible that there’s a leak or clog in the water supply line. Your toilet tank may still fill with water with clogs and leaks, but very slowly. If your issue is the low water pressure is caused by a leak, the most likely location is at the water supply valve. 

How to Fix 

The most straightforward toilet problem in the world is if someone forgot to turn the water supply back on. Simply twist the valve on the supply line to the ON position, and you’re good to go. Clogs and leaks in the waterline, however, are a bit trickier. You’ll have to turn off the water supply to the entire house and drain the waterline. 

Next, disconnect the water supply line from the toilet and replace it and the water supply valve with new ones. If this doesn’t fix the problem, the issue may be in one of the main supply lines. If this is the case, you should turn over the job to a professional plumber. 

Faulty Fill Valve 

A faulty fill valve will cause a similar issue to a water supply problem. The fill valves’ only responsibility is to fill the toilet tank and bowl with water after the flush cycle is complete. The toilet fill valve is usually gets located on the left side of the toilet opposite the overflow tube. 

Depending on the type of water you have, mineral deposits can build up in the fill valve and cause a clog. Sediment deposits and old ages are possible reasons and definite signs of a faulty fill valve. Regardless of the problem stems from, however, the only way forward is to repair or replace the part. 

How to Fix 

The easiest way to get your toilet working again if the fill valve is the problem is simply to replace it. They’re relatively inexpensive and easy to install, especially those with some DIY or plumbing experience. 

  1. Turn the water line supply to the toilet OFF. 
  2. Lift the lid atop the toilet tank and set it aside. 
  3. Give the water level a double-check to make sure they’re low. 
  4. Flush the toilet to get rid of any water in the tank. 
  5. Use one hand to hold the bottom of the fill valve while using your other hand to give the top a ⅛ counterclockwise turn to loosen and remove it. 
  6. Inspect the tiny holes that allow water to flow into the tank for debris or blockage. 
  7. Use water or a screwdriver to poke debris free from the hole and open things up. 
  8. Removing debris could be a simple fix to the problem, but you can also opt to remove and replace the fill valve if it appears old or damaged. 
  9. To replace the fill valve, simply remove it and all its components from the toilet tank. 
  10. Install the new fill valve in its place, following the directions to a T. 

Issues with the fill valve are the most common reasons for a toilet tank that won’t fill. Therefore, it’s important to know how to service, repair, or replace the valve when necessary. 

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Problems With the Float 

The float is the part of the flushing process that tells your water supply when the tank is full, and it can stop releasing water into it. As the water level in the tank rises back to the top, the float rises with it. The float looks like a softball-sized balloon on older toilets and features a float arm and a float ball. On newer toilets, the float is attached to the side of the overflow tube and doesn’t float. 

Regardless of how your float looks, it can cause the same issues. If it’s set too low, gets stuck, or malfunctions for some reason, it won’t signal to the fill valve that it needs more water in the tank. The result is that water will shut off prematurely, and the tank won’t fill. 

How to Fix 

The easiest fix for your float is to readjust it and put it higher in the tank so that water rises high enough. However, if the issue is linked to the float itself rather than where it’s at, you’ll have to pursue other repairs. Your best bet is to replace the float. You can do this yourself by purchasing one at your local hardware store or contacting a local plumber to do the job. 

  1. Ensure the water gets turned off to the toilet as with all toilet repairs. 
  2. Remove the tank lid and set it aside. 
  3. Take note of which type of float system you have because you’ll perform different adjustments on them. 
  4. There should be a small screw with a float ball system where the float arm connects to the fill valve. 
  5. Use a Phillips screwdriver and turn the adjustment screw counterclockwise to raise the float ball and water levels. 
  6. With a float cup, there should be a long, plastic adjustment screw attached to the side of the float. 
  7. Turn it clockwise with your hand or a screwdriver to raise the water levels. 
  8. Your end goal should be for the water level to be around ½ inches below the top of the overflow tube. 

Your Toilet Flapper is Bad

Your flappers’ job is to form a perfect seal around the flush tube of your toilet and keep water from flowing into the bowl. When you flush your toilet, the flapper lifts and allows water to flow from the tank to the toilet. If you have an older toilet with an old flapper, there’s a good chance that it’s worn or that sediment deposits have gathered underneath it and won’t allow it to seal. 

If your flapper is the problem, likely, you’re also experiencing the problem of constantly running water. When this happens, the flow of is non-stop through the refill valve and flush tube at the bottom of the tank and into the bottom of your toilet bowl. Essentially, it’s like a non-stop flush cycle because water will continue to flow from the tank to the bowl. 

How to Fix 

If you think that your flapper is the issue, but it doesn’t appear bent, corroded, or twisted, you can fix it. 

  1. Turn off the water supply to the toilet. 
  2. Flush the toilet to empty the tank. 
  3. Manually lift the flapper and inspect the seal on the bottom. 
  4. If there are mineral deposits, you can use a soft brush, vinegar, and baking soda to wipe them away. 
  5. However, if the flapper is bent, twisted, or corroded, you’re better off removing it and installing a new flapper. 

The Trip Assembly 

The trip assembly refers to the toilet handle, the arm inside the toilet, and the flapper chain connected to it. These components can malfunction and cause a toilet problem, a running toilet, or you do not have enough water in your tank. A bent trip assembly, an old slack chain, or a disconnected chain can all be problems with the trip assembly. 

How to Fix 

If the trip assembly is bent or twisted, you can use your hands to twist it back into the proper position. Keep in mind that the material these things get made of is plastic, so be very gentle with them. 

If the problem lies with a slack chain, you can loosen it from the toilet arm and reattach it so that it’s tighter. You can do the same thing on the flapper side, but it’s usually easier to access and work with the lever arm. 

However, trip assemblies are relatively inexpensive pieces of equipment and are very easy to replace. It’s also one of the most common causes of toilet problems, which means that the necessary toilet parts will be readily available at your local hardware store. 

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Relates Questions 

Can I fix my toilet if I’m not a handy person? 

While it’s always best to have at least limited plumbing experience, toilets are fairly straightforward and often require easy fixes. As long as you have Google and the right tools, anyone can fix toilet problems. However, for more in-depth issues such as leaks or plumbing problems, you should contact a plumbing professional. 

Why won’t my toilet stop running? 

If you have the dual problem of a tank that won’t fill and a toilet that won’t stop running, the most likely culprit is your flapper. If the flapper doesn’t form a perfect seal around the flush valve, tank water will flow through the flush valve and into your toilet bowl or down your drain. 

What is the most common issue with a toilet that won’t fill? 

Each of the problems we’ve looked at is fairly common. However, issues with the fill valve and the flapper are most common in terms of overall popularity. If you experience one problem after the other with your toilet, you’re better off replacing it with a newer toilet. New toilets aren’t costly, and they will solve many issues. 

Final Thoughts 

As you can see, toilets aren’t overly complicated to operate, but they have a surprising number of moving parts. Each of these components plays a vital role in its operation. If your toilet won’t fill with water, your best bet is to go through each problem individually until you find the culprit. This process of elimination takes time, but it’s what a professional plumber would do, so it’s what you should do. 

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Hubert Miles

I've been conducting professional home inspections since 2002. I'm a licensed Home Inspector, Certified Professional Inspector (CPI), Certified Master Inspector (CMI), and FHA 203k Consultant. I started to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
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