If a toilet fill valve won’t shut off, the toilet will run continuously and waste many gallons of water. There are a few reasons this can happen. The valve may be old, dirty, rusty, or damaged. A broken valve can leak and be unable to close. However, you don’t always need a plumber to fix a toilet fill valve. We’ll explain how you can deal with the situation before calling a technician.

What Is a Toilet Fill Valve?

The fill valve shuts off the flow of water when the tank has filled. It’s part of the flush assembly, opening and closing as you flush the toilet. While it’s open, water can enter and refill the tank. A toilet fill valve can be a float ball type with a round ball and float arm. The float cup type is more common in modern toilets.

How to Repair a Toilet Fill Valve

It is generally not difficult to fix a toilet fill valve (it’s usually located behind the toilet). Here are some steps you can take to address the issue:

• Loosen the Valve: Gently wiggle the valve back and forth in alternating clockwise and counterclockwise motions. It should loosen until you can turn it and shut it off. 
• Tighten the Screw: The fill valve has a central screw that holds it together. If the valve won’t loosen, hold it with a pair of pliers and tighten this screw.
• Heat the Valve: Fill a small bucket with hot water and soak a cloth. Place the hot cloth on the valve (while wearing rubber gloves to avoid burning your hands). After a couple of minutes, the valve should warm up and be easier to close.

Another effective method is to heat the valve with a hairdryer.

• Use a Spray Lubricant: You can use WD-40, which won’t damage the rubber washer. Spray it onto the valve and leave it for 10 minutes. You should then be able to turn the valve.

Replace the Toilet Fill Valve

If the toilet fill valve doesn’t shut off, it may need to be replaced. To replace the valve, turn off the main water supply shut-off valve (it’s usually in the basement or laundry room). Next, remove excess water from the pipes by turning on a faucet lower than the toilet valve. Water will flow down the pipes until there’s none left to supply the toilet tank. 

Place a bucket under the toilet shut-off valve and close the toilet supply line. Using a crescent wrench, disconnect the supply line and valve by removing the bolt connecting them. Now you can remove the shut-off valve. If it has a compression joint, use the wrench to remove the bolt holding the pipe to the valve, while holding the pipe with pliers. If the valve has sweated copper pipes, use a tube cutter, leaving enough pipe from the wall to install a new fitting.

To install the new valve, place a compression nut on the toilet pipe. Attach the valve to it, using a pair of crescent wrenches to secure the compression nut to the valve’s stem threads. Make sure the valve’s outlet faces upward. You can now turn on the toilet supply and main water supply lines.

Look For Other Sources of the Problem

Other issues can cause a running toilet. If it’s not because the toilet fill valve won’t shut off, the source of the problem may be the:

• Flapper: A cracked flapper (tank ball) can fill with water as the tank drains, causing it to close too soon. The part can also deteriorate over time and provide an ineffective seal.
• Flush Valve: The flapper rests on the flush valve. If this valve is chipped or eroded, it may not be sealing the water in the tank and should be replaced.
• Flush Lever: If the flush lever isn’t tightly secured to the tank, try to tighten its lock nut. If any parts are worn, bent, or separated, install a new flush lever assembly.
• Float Cup: Adjust the fill height if the float cup is positioned too high. If so, water can enter the overflow tube and then the toilet bowl, causing the fill valve to keep turning on.
• Flush Handle/Flapper Chain: A faulty flush handle or short flapper chain can cause the toilet to cycle continuously.
• Stopper Valve: An improperly seated stopper valve won’t provide a good seal, causing your toilet to run. To fix the issue, adjust the valve’s hinges or replace it.

If the toilet fill valve is the source of the problem, the signs (aside from a running toilet) can include a hissing noise or a leak from the supply line coupling. Call a plumber if you can’t resolve the issue or aren’t comfortable attempting a DIY fix.

Contact Us If Your Toilet Fill Valve Won’t Shut Off

At Sky Heating & Air Conditioning, our licensed plumbers can provide any type of toilet repair. They can replace the fill valve and, if necessary, replace the toilet. Whether the unit is running constantly, leaking, or not flushing, a technician will arrive at your Portland or The Dalles home promptly and fix the issue quickly. Use our online contact form or call (888) 900-2109 to request help.