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Fix a toilet that will not fill

We'll check the water supply, fill valve, and float—then fix the cause or tell you when to call a plumber.

Troubleshooting · Home plumbing
10–25 min
What you'll need
  • Replacement fill valve (if needed)
  • Towel to protect the lid and catch drips
Step 1 of 6

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Steps

Goal: Confirm the symptom, check the water supply, then isolate the cause—fill valve or float.

  • Flush the toilet and watch the tank.
  • Good: The tank does not refill or refills very slowly—fill fault. Proceed to Check water supply.
  • Bad: The tank fills normally—no problem.

Check water supply

Goal: Rule out supply valve and line issues.

  • Locate the supply valve behind the toilet. Turn it counterclockwise to open fully.
  • Inspect the supply line for kinks, crushing, or leaks. Replace if damaged.
  • Good: Valve open and line clear. Proceed to Fill valve.
  • Bad: Valve will not open or line is damaged—call a plumber.

Fill valve

Goal: Clean, adjust, or replace the fill valve and float.

  • Lift the tank lid. Flush and watch the fill valve. If no water flows, turn off the supply, remove the fill valve cap, and rinse the filter screen. Reinstall and turn the water on.
  • Check the float moves freely. Adjust so the water level sits about one inch below the overflow tube.
  • Good: Fill valve flows and float is set correctly—the tank should fill.
  • Bad: Fill valve still does not flow—replace it or call a plumber.

When to get help

Call a plumber if:

  • You have opened the supply valve and cleaned the fill valve but the tank still does not fill.
  • The supply line is leaking.
  • No water flows from the supply when the valve is open.
  • You are not comfortable replacing the fill valve.

Verification

  • The tank refills after a flush.
  • The water level sits about one inch below the overflow tube.
  • The fill valve shuts off when the tank is full.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Verify the tank does not refill after a flush.
  2. Water supply Check the supply valve and line.
  3. Fill valve and float Clean, adjust, or replace the fill valve and float.
  4. Call a plumber Supply blocked, line leaking, or repeated failures—call a plumber.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Whether the supply valve is open
  • Whether water flows from the supply line
  • Fill valve and float condition
  • Steps already tried

Does the tank not refill after a flush?

Flush the toilet. If the tank does not refill or refills very slowly, the fill system has failed.

Flush the toilet. Watch the tank. Good: tank does not fill or fills slowly—fill fault. Bad: tank fills normally—no problem.

Yes No

You can change your answer later.

No action needed

The tank fills normally—no problem. No action needed.

Done

Is the supply valve fully open?

The valve behind the toilet must be open for water to reach the tank.

Locate the supply valve behind the toilet. Turn it counterclockwise to open fully. Check the supply line for kinks or leaks. Good: valve open and line clear. Bad: valve closed or line damaged—open valve or replace line.

Yes No

You can change your answer later.

Does the fill valve flow when the tank is empty?

Flush and watch the fill valve. Water should flow into the tank.

Lift the tank lid. Flush and watch the fill valve. Good: water flows—check float adjustment. Bad: no flow—clean or replace fill valve.

Yes No

You can change your answer later.

Is the float free to move and set correctly?

A stuck or misadjusted float can stop the tank from filling.

Check the float moves freely. Adjust so the water level sits about one inch below the overflow tube. Good: float works—tank should fill. Bad: float stuck or broken—replace fill valve or call a plumber.
Question

Is the float working?

Continue

You can change your answer later.

Call a plumber

Call a plumber if you have opened the supply valve and cleaned the fill valve but the tank still does not fill, if the supply line is leaking, or if no water flows from the supply when the valve is open.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a toilet tank not fill?
Common causes: water supply valve closed or partially closed, clogged or faulty fill valve, stuck or broken float, or a kinked or blocked supply line. Check the supply valve first, then the fill valve.
Can I fix a toilet that will not fill myself?
Yes. You can open the supply valve, clean the fill valve, and adjust or replace the float. A new fill valve costs about $15–30 and is a common DIY repair.
When should I call a plumber for a toilet that will not fill?
Call a plumber if you have opened the supply valve and cleaned the fill valve but the tank still does not fill, if the supply line is leaking, or if no water flows from the supply when the valve is open.

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