Quick answer
Turn off the water supply under the toilet. Check the fill valve for clogs or damage and replace if needed. Ensure the float arm isn't stuck or misaligned.
Confirm the symptom
- Toilet tank doesn't refill after flushing
- Water shuts off immediately after flush
- Toilet bowl water level drops but tank doesn't refill
Tools and prep
- Adjustable wrench
- Screwdriver
- Plumber's putty
- Replacement fill valve or flapper
- Bucket or towel
- Turn off water supply valve
- Wipe up any spilled water before starting
Step-by-step troubleshooting
- Check Water Supply ValveDo: Locate and ensure the water supply valve under the toilet is fully open.Observe: Water flows freely to the tank.Means: Valve is open and functional.Next: If valve is closed, open it and wait 10 minutes to see if the tank fills.
- Inspect Fill ValveDo: Look inside the tank for the fill valve. Check for clogs, cracks, or damage.Observe: Fill valve is clogged or damaged.Means: Valve needs cleaning or replacement.Next: Clean the valve or replace it with a new one.
- Adjust Float ArmDo: Check the float arm to see if it's stuck or misaligned.Observe: Float arm moves freely and reaches the correct water level.Means: Float arm is functioning properly.Next: Adjust the float arm if it's misaligned.
- Test Flapper ValveDo: Press down on the flapper valve to see if it seals properly.Observe: Water leaks from the tank to the bowl when the flapper is pressed.Means: Flapper is worn or damaged.Next: Replace the flapper valve.
- Check for Clogs in Inlet TubeDo: Inspect the inlet tube for mineral buildup or clogs.Observe: Inlet tube is clogged with debris.Means: Inlet tube needs cleaning.Next: Clean the inlet tube with a wire or replace it if necessary.
- Verify Tank Water LevelDo: Check the water level in the tank. It should be about 1 inch below the overflow tube.Observe: Water level is too low or too high.Means: Adjust the float arm or fill valve to set the correct water level.Next: Adjust the float or fill valve as needed.
Common causes
| Cause | Likelihood | Difficulty | Part often needed |
|---|---|---|---|
| Clogged or faulty fill valve The fill valve may be blocked by mineral deposits or damaged, preventing water from entering the tank. | Common | Easy–Medium | Fill valve |
| Closed water supply valve If the shut-off valve under the toilet is closed, water cannot flow into the tank. | Common | Easy | None |
| Stuck or misaligned float arm A float arm that is stuck or improperly adjusted can prevent the tank from filling to the correct level. | Common | Easy | Float arm or fill valve |
| Worn or damaged flapper valve A faulty flapper can cause water to leak into the bowl, lowering the tank water level. | Sometimes | Easy | Flapper valve |
| Clogged inlet tube Mineral buildup in the inlet tube can restrict water flow to the fill valve. | Sometimes | Easy | Inlet tube |
| Faulty overflow tube If the overflow tube is damaged or improperly positioned, water may not fill the tank correctly. | Rare | Medium | Overflow tube |
Parts matching
Common parts needed for a toilet tank not filling up after flush:
- Fill valve: Controls water flow into the tank.
- Flapper valve: Seals water in the tank until flushed.
- Float arm: Regulates the water level in the tank.
- Inlet tube: Connects the water supply to the fill valve.
Purchase parts compatible with your toilet model for the best results.
When to call a professional
- The tank still doesn't fill after replacing the fill valve and flapper.
- Water continues to leak from the tank despite repairs.
- You notice cracks or damage to the toilet tank itself.
- The issue persists after multiple attempts to fix it.
FAQ
Why is my toilet tank not filling after I replace the fill valve?
Ensure the new fill valve is properly installed and the water supply valve is fully open. Check for clogs in the inlet tube.
Can a low water pressure cause the toilet tank to not fill?
Yes, low water pressure can prevent the tank from filling properly. Check your home's water pressure and ensure it's within the normal range (40–80 psi).
How do I know if the float arm is the problem?
If the float arm is stuck or not moving freely, it can prevent the tank from filling. Try adjusting or replacing the float arm to see if it resolves the issue.
Is it normal for the toilet tank to take a long time to fill?
No, the tank should fill within a few minutes. A long fill time may indicate a clog or a faulty fill valve.