How to Change the Toilet Fill Valve Assembly to Fix a Continuously Running Toilet

Table of Contents

If simple adjustments to stop a toilet from running don’t do the trick, then you may have to change out the toilet fill valve. 

Fill valve replacement is simple, and if you know how the thing works, you’ll find it even easier. So, before we start changing a fill valve, we’ll start with how they work to fill your toilet tank with water.

The toilet fill valve assembly

Looking at your toilet from the front you’ll notice there’s a connection to the wall. This is the water connection to your home’s plumbing. There’s a valve on the wall, from the valve you’ll find a piece of tubing leading to the bottom of the toilet tank.

The connection on the bottom of the toilet tank is part of the toilet fill valve assembly. The toilet fill valve is a complete assembly that you can purchase from the hardware store. Part of this assembly is a threaded portion that slips through a hole in the bottom of the toilet fill tank. It’s this threaded connection that you see the tubing from the wall connected too.

The toilet fill valve gasket

The toilet fill valve needs a watertight seal between the tank and the tubing connection to the wall. The toilet fill valve gasket is the piece that does this job.

Looking at the outside bottom of the toilet tank you’ll see the threaded connection of the toilet fill valve. On this connection two things happen. First, there’s the nut that tightens against the porcelain bottom of the toilet tank. Second, there’s the nut that connects the pipe from the wall valve to the fill valve.

From the inside of the tank you’ll see a rubber gasket between the bottom of the fill valve assembly and the inside porcelain. This is the toilet fill valve gasket. 

When you remove the nut from the outside bottom of the porcelain tank this gasket will loosen. Naturally, if you loosen the nut when there is water in the tank, water will leak from the opening. So, keeping this gasket compressed against the inside of the tank keeps the water in the tank, not on your floor.

The toilet fill valve ballcock

The rest of the fill valve assembly you see on the inside of the toilet water tank is the fill valve ballcock. The ball cock opens and closes when the water level in the toilet tank lowers or raises. Lower water levels, the ballcock opens letting water flow from the wall valve. Higher water level, the ballcock closes stopping the water flow from the wall valve.

If the ballcock doesn’t close well when the water level raises, it won’t stop the water flow from the wall valve. And that’s why your toilet is constantly running if your toilet fill valve, and its ballcock is old and worn.

And that gets us to replacing your toilet fill valve assembly.

Ten steps to remove and replace the toilet fill valve assembly

  • Step one: Prepare a bucket, a sponge, a pipe wrench, and some dry towels and place them near the work area. You’ll be dealing with some leaking water.
  • Step two: Close the wall valve and then flush the toilet. If you watch the fill valve assembly after you flush, you’ll see the float go down with the water level. As discussed above, this would be when the ballcock opens allowing water to flow from the wall valve.  But since we have the valve closed, there is no water flow refilling the tank.
  • Step three: Scoop the remaining water from the bottom of the toilet tank.  Even though you’ve flushed and there is no water coming in from the wall valve, there will still be water in the bottom of the tank. Before you go further, with a paper cup scoop the water as best you can and put it either in the toilet bowl or the bucket. When you can’t scoop anymore water use a dry towel to sop up the rest.
  • Step four: With the tank empty and dry, grab the nut of the pipe connected to the threads of the protruding part of the fill valve assembly. This is the part located on the bottom of the porcelain tank. Adjust the pipe wrench to grasp the nut and give it a twist counterclockwise. Once lose you can set the wrench aside and remove the nut by hand.
  • Step five: The nut at the bottom of the porcelain is the nut that compresses the gasket inside the tank as discussed above. With your hand, or wrench if needed, twist the nut counterclockwise. Unthread the nut entirely from the threads.
  • Step six: From the inside of the toilet tank, grab the entire fill valve assembly and gently lift it from the tank. Notice that there is a small tube that is attached to a stand tube near the center of the tank. There’s usually a little clip, remove the clip and raise the tube with the assembly.
  • Step seven: From the inside of the tank, grab the new fill valve assembly and place it inside the tank. Be sure the threaded portion protrudes through the bottom of the porcelain and be sure that the fill valve gasket is between the inside porcelain and the bottom of the fill valve assembly. This is the gasket that will seal the tank from water leaks as discussed above.
  • Step eight: From the bottom of the tank, grab the new fill valve assembly nut and thread it onto the threads. Tighten the nut firmly giving it a firm turn with the wrench if needed to make sure the gasket is sealed.
  • Step nine: Reattach the water line nut. Twist the nut clockwise until firmly seated. If needed give the nut a firm turn with the wrench.
  • Step ten: Reattach the small fill tube with the clip on the inside of the tank and turn on the wall valve. Check for leaks and tighten connections if needed.

Adjusting the new toilet fill valve

When you turned the water on, water should flow into the tank raising the ballcock float. When the float is adjusted correctly the ballcock will close at the top level. If you see, or hear that water is still flowing you’ll need to adjust the float.

If your float is a ball floating off an arm, then you need to twist the ball counterclockwise. Notice there are threads at the base of the ball. Just like a beach ball under water, you want to put the ball further beneath the water line. This is what causes the ball cock to close.

If your float is the new style that floats up and down the tube of the fill valve assembly like an elevator, you’ll notice a place to put a screwdriver. Using a screwdriver, adjust the float so it goes deeper below the water level. This will cause the ballcock to close hard stopping water flow.

Completing the replacement of the toilet fill valve assembly

At this point you have successfully changed out a toilet fill valve assembly. If you’re still having problems, then you may have a flapper that’s not seating tightly against the bottom flush hole to the toilet bowl. If so, you’ll have to replace the toilet flapper.

You can always give Fountain plumbing a call. We serve Tyler, Texas for every plumbing need. Give us a ring if you need some help, we’ll be glad to help you along and fix your leaking toilet fill valve assembly.