How to Replace a Toilet Fill Valve?

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Most people don’t know the first thing about fill valves, but it’s perfectly fine — you don’t want to mess with it until it’s broken.

But now you are reading this post, so we can safely assume that your fill valve is ready for replacement. How do you replace a toilet fill valve?

It’s a four-step process. You must empty the toilet tank, remove the old fill valve, install a new item, and turn on the water supply. The whole process is slightly harder, but you’ll figure it out after reading this article.

Tools You’ll Need to Replace the Fill Tube

A toilet fill valve is easy to access, which means you won’t need many tools to change it. Here is the list of necessary equipment:

  • A sponge to empty the toilet tank
  • A bucket to collect the remaining water from the tank
  • Pliers or an adjustable wrench
  • A new toilet fill valve

Even if you don’t have one of these tools, you’ll probably replace the fill valve without it. The only exception is the actual fill valve — you can’t repair the toilet without a new model.

A Step-by-Step Guide on How to Replace a Toilet Fill Valve

We already showed you the basic steps, but it’s important to delve deeper into the fill valve replacement process. That’s the only way to install a new valve without causing toilet tank leaks.

Step 1: Empty the Toilet Tank

The first task is to close the water supply line and empty the tank. There is a small valve next to your toilet or behind it. You need to turn its knob clockwise to prevent water from flowing into the toilet tank.

In case the shutoff valve is too stiff to shut off, use WD-40 penetrating oil to loosen it. The substance requires only 10 minutes to work, so you can tighten the valve after that.

Now you can empty the tank – flush the toilet, and hold down the flush lever until all of the water flows out of the tank. Without water in the tank, you are free to open the lid with your hands or a flathead screwdriver.

Take a dry sponge and wipe the tank bottom with it. It’s a simple way to collect the remaining droplets from the tank, and it helps you avoid getting dirty and wet while working.

Finally, you can detach the water supply line hose. It’s a metal tube that transfers water from the shutoff valve to the toilet tank — it connects directly to the toilet fill valve. You’ll probably see the water supply tube touching the bottom of the toilet tank.

Step 2: Detach the Old Fill Valve

Detaching the old toilet fill valve is the second step in this process. You can do it with your hands, but sometimes you might need pliers to unscrew the fill valve’s lock nut. 

The lock nut is a metal ring right under the toilet tank, and it secures the toilet fill valve. When you use pliers, do it softly because the toilet tank is plastic — it can crack if you push too hard. 

When you unscrew the nut, remember to remove the refill tube that leads from the toilet fill valve to the overflow pipe. After that, you can disconnect the fill valve. 

Pick it with your hands — the plastic coupling is lightweight, requiring little to no force to lift it.

Pro Tip: You might as well clean the toilet tank while it’s open. You probably don’t do it frequently, so seize the chance to clean the inside of the tank. It will prevent black mold from forming in your toilet.

Step 3: Install the New Fill Valve

Installation is the third step, and it’s probably the easiest one. You need to place the new fill valve in the correct position and then secure it with the lock nut.

Put the new fill valve on its gasket — it’s a rubber opening that seals the inlet hole in the toilet tank. Our advice is to check whether the gasket is functional — if you notice it’s worn out, perhaps it’s best to replace the gasket as well.

Once the fill valve is in its position, you should check its height — the part should sit a couple of inches below the tank top. At the same time, the fill valve must be two inches higher than the overflow tube.

If the position is right, you can put back the refill tube that connects the toilet fill valve with the overflow pipe. After that, secure the fill valve by screwing the threaded nut under the toilet tank.

The nut must seal well clockwise to prevent leaks. The last task is to attach the water supply tube to the fill valve.

Step 4: Open the Water Supply Valve

The last step is to open the shutoff valve. Turn it counterclockwise — you’ll feel it rotating easily because you already sprayed it with WD-40 penetrating oil. However, remember to check for leaks around the toilet fill valve and toilet tank.

This is crucial because it’s not hard to damage something while replacing the fill valve. If everything’s in order, flush the toilet and watch how the new fill valve does its job.

How Do You Know the Fill Valve Is Damaged?

How can you tell that your fill valve is not working? Sometimes it’s difficult, but there are three common signs you should look for.

Firstly, your toilet tank is not filling with water, or it’s taking too long to refill. It’s a clear signal that the toilet fill valve is not working because that’s the only purpose of this item.

Secondly, you may notice that the water can’t stop running out of the toilet. The problem occurs when the fill valve can’t close — it keeps sending water to the tank, so the overflow tube constantly sends excess water to the toilet bowl.

Thirdly, you’ll know that the fill valve is damaged because the flush system is too weak. It’s easy to figure out why — the fill valve doesn’t allow water into the tank, so your toilet doesn’t flush strongly enough to remove waste.

inside toilet tank

How Does Your Fill Valve Work?

You probably want to replace a toilet fill valve and forget about it, but we want to indulge the most curious readers, too. Toilets are relatively simple mechanisms where each part has a highly specific role.

That’s the case with the toilet fill valve, as its purpose is to help the tank load with water after flushing. Here’s how the entire structure functions.

It all begins with you flushing the toilet — you press the flush handle, and it triggers a chain reaction. The handle has a long arm inside the tank, which raises a metal chain to lift the toilet flapper.

The flapper sits on the flush valve opening, so it lifts and allows water to exit the tank when you flush the toilet. As the water drains, the toilet flapper slowly returns to its primary position.

As the water goes down the drain, the tank float (a plastic ball) lowers to reach the bottom of the tank. In the process, the tank float opens the fill valve, and the tank starts refilling.

The float controls the water level in the tank, so refilling stops when it reaches the original position.

On the other hand, the refill tube connects the fill valve with the overflow tube — its main purpose is to send some water back into the bowl after flushing. That stops bad smells from going back into the bathroom.

The mission of the overflow tube is to control the fill valve. A broken fill valve keeps sending water into the tank, so the overflow tube releases some of it to the toilet bowl to prevent the tank overflow. 

Finally, a water supply tube brings water from the main supply system to the toilet tank.

The Bottom Line

Replacing the fill valve is probably not how you want to spend your afternoon, but it’s necessary because the toilet can’t work without it. The good thing is the simplicity of the process:

  • Close the water shutoff valve and empty the tank
  • Remove the broken fill valve
  • Insert the new fill valve
  • Open the water supply line

Follow our instructions, and you’ll replace the fill valve quickly. Are you ready to give it a go?


Is it hard to replace a toilet fill valve?

It’s not hard to replace a toilet fill valve. On the contrary, you can do it in minutes if you already have a new fill valve available. The process of installing a new fill valve is easy even for inexperienced homeowners.

To replace the toilet fill valve, you need to close the water supply. Then, remove the old valve and install a new toilet fill valve. After that, you can open the water supply and use your toilet again.

Are toilet fill valves universal?

Toilet fill valves are not universal. Although most of them can fit the same rubber gasket, there are differences in shapes and sizes. That’s why you have to pay attention to the dimensions of the fill valve before purchasing a new item.

If the old valve worked properly for years, we suggest buying the same model. That way, you don’t need to think about the details — all it takes is to install the same type of toilet fill valve.

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