The toilet fill valve controls how water enters the toilet tank after each flush. When this component wears out or becomes clogged with mineral deposits, the toilet may refill slowly, fail to refill at all, or continue running after flushing.
Replacing an old or defective fill valve is a straightforward repair that usually takes less than 30 minutes and requires only basic tools. Start by confirming the symptoms below, then follow the steps to install a new fill valve.
Quick Answer
A faulty fill valve can prevent the toilet tank from refilling properly or cause the toilet to run continuously. Replacing the fill valve typically restores normal refill operation.
Common Signs of a Faulty Fill Valve
- Toilet tank does not refill after flushing
- Tank fills very slowly
- Toilet continues running after refill
- Hissing sound comes from inside the tank
- Refill flow of water is inconsistent or weak
Likely Causes
Fill valve problems commonly result from:
- Internal wear of valve components
- Mineral or sediment buildup
- Stuck or misaligned float
- Aging plastic parts
- Debris entering plumbing after work on water pipes
Tools & Materials
You may need:
- Replacement fill valve kit
- Adjustable wrench or pliers
- Sponge or towel
- Bucket
- Rubber gloves
Most fill valve kits include installation hardware and adjustment instructions.
Step-by-Step: How to Replace a Toilet Fill Valve
1. Shut Off Water and Empty the Tank
Turn the water shutoff valve clockwise to stop water flow.
Flush the toilet and hold the handle down to empty the tank. Use a sponge or towel to remove remaining water.
Disconnect the supply line from the bottom of the tank.
2. Remove the Old Fill Valve
Inside the tank, disconnect the small refill tube from the overflow tube.
From underneath the tank, loosen the retaining nut that holds the fill valve in place.
Lift the old valve assembly out of the tank.
3. Prepare the New Fill Valve
Adjust the height of the new fill valve according to manufacturer instructions.
The top of the valve should sit slightly above the overflow tube once installed.
Insert the valve through the tank opening.
4. Secure the Valve
Install the mounting nut beneath the tank and tighten it by hand, then snug slightly with pliers.
Avoid over-tightening, which can damage the tank.
Reconnect the water supply line to the valve inlet.
5. Connect the Refill Tube
Attach the small refill tube from the fill valve to the overflow tube.
Use the clip provided with the valve kit to hold the tube in place.
6. Restore Water and Adjust the Float
Turn the water supply back on and allow the tank to fill.
Adjust the float so the water level stops about 1/2 inch below the top of the overflow tube.
Flush several times to confirm normal operation.
When the Problem May Be More Serious
If the toilet still fails to refill properly after replacing the fill valve, the issue may involve:
- Low household water pressure
- Blocked water supply line
- Faulty shutoff valve
- Internal plumbing restrictions
If other fixtures also show weak water flow, you’ll need to call a plumber.
Preventing Future Fill Valve Problems
- Periodically inspect tank components
- Replace an aging fill valve before it fails
- Flush plumbing at faucets after municipal water work
- Avoid debris entering supply lines during repairs
To Hire a Plumber…
If the repair turns out to be more complicated than expected, you can always find a plumber near you.
For hiring advice, see Trade Secrets for Hiring the Right Plumber.
Related Articles
If you’re not sure what’s causing the problem, see our
Toilet Repair and Troubleshooting Guide for a complete diagnostic overview.
Also see:
