What is a Toilet Fill Valve?

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  • Written By: Lori Kilchermann
  • Edited By: Lauren Fritsky
  • Last Modified Date: 15 March 2020
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A toilet fill valve is located in the tank portion of a toilet and controls the water flowing into the tank. Attached to the float mechanism, the toilet fill valve is activated when the float begins to drop in the tank. Once the water reaches its predetermined full level, the toilet fill valve closes and halts the flow of water into the toilet tank.

Made of plastic, the toilet fill valve is not subject to corrosion or rust; however, scale as well as mineral build-up from hard water can occasionally render the valve inoperable. Most in-bowl toilet-cleaning chemicals can prevent this build-up and keep the toilet fill valve in working condition for years. Proper float adjustment is critical for long toilet fill valve life, as most broken fill valves are due to improperly functioning floats.

The fill valve is located in the toilet tank directly above the incoming water line. In order to replace the fill valve, the water must first be turned off at the water line. With the water off, the toilet can be flushed and drained of its water supply. This will provide ample dry room to remove the toilet fill valve and replace it with another valve. It is a wise decision for users to replace the float and flapper mechanism at the same time to prevent having to drain the system again at a later date.


Once the fill valve is replaced, the water can once again be turned on. The float must be set to turn the water off as it reaches the full level. Typically, the float can be adjusted by bending the metal rod that attaches it to the fill valve. To turn the water flow off, the float ball must be bent down toward the water. This will cause the fill valve to close sooner; conversely, bending the rod upward will allow the water to flow longer before tripping the fill valve and shutting off the flow.

A properly-operating toilet fill valve will be silent once the tank has reached its full water level. Any noise or sound coming from the tank is an indication that water is continuing to flow out of the fill valve. Typically, a minor adjustment to the float arm will correct this problem. Other reasons that the fill valve may continue to allow water to flow into the tank are sticking flapper valves or an incorrectly-adjusted flushing arm chain. To cure this problem, users should make certain that the chain is letting the flapper valve close completely.


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Post 2

The way it was explained to me at the home improvement store, it was much easier to replace the entire toilet fill valve instead of trying to open the unit up and repair it. I thought I might need to hire a professional plumber to install the new toilet tank fill valve and flapper valve, but I watched a home repair show on PBS and figured out how to do it myself.

The worst part about the removal and installation of toilet parts, at least to me, is the cramped and messy work space. It's not always easy to reach the bolts that hold things in place, and when you do reach them, they're usually wet and dirty. I managed to get the old toilet fill valve assembly removed, but I had trouble seating the new one in place at first. A second pair of hands would have helped.

Post 1

You wouldn't thing a toilet tank fill valve would be that problematic, but I've had to replace two of them since I installed this toilet in our guest house in 1998. The first one had just worn out from years of service, but the second one was clearly defective from the start. Water wouldn't flow through through the tube and into the tank. Instead, it dribbled out of the sides of the valve assembly. Eventually enough water would leak out that the float would stop the flow, but it took a long time for the tank to refill between flushes.

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