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How to Replace a Toilet Fill Valve - DIY Guide

A faulty or noisy fill valve is another common cause of a running toilet. Replacing it is an easy DIY job that takes about 15–20 minutes.

Hands holding a toilet fill valve with a black tube in a bathroom with white tiled walls, showcasing plumbing repair work.

What You’ll Need

  • Replacement fill valve

  • Adjustable wrench or channel-lock pliers

  • Towel or small bucket


1. Turn Off the Water

Locate the shut-off valve behind the toilet and turn it clockwise until the water stops.


2. Drain the Tank

  • Flush the toilet to empty most of the water.

  • Hold the handle down if needed to get as much out as possible.

  • Use a towel to soak up any remaining water at the bottom of the tank.


3. Disconnect the Water Supply Line

Under the tank, loosen the nut that attaches the supply line to the fill valve. Place a towel or bucket underneath to catch drips.


4. Remove the Old Fill Valve

Inside the tank:

  • Unscrew the large plastic nut holding the valve in place (usually hand-tight).

  • Lift the old fill valve straight up and out.


5. Install the New Fill Valve

  • Adjust the height of the new valve so the top sits 1 inch above the overflow tube.

  • Insert it into the tank opening.

  • Tighten the locknut underneath by hand—then snug it gently with pliers.

Tip: Don’t overtighten; it can crack the tank or damage the plastic threads.


6. Reconnect the Water Supply Line

Attach the supply line and tighten until secure. Make sure the refill tube clips onto the overflow pipe correctly.


7. Turn On the Water and Test

  • Turn the shut-off valve counterclockwise to restore water flow.

  • Let the tank fill.

  • Adjust the float height if needed so the water stops at the correct level.

Watch for leaks around the base of the fill valve or supply line.


You’re Done!

A new fill valve should stop hissing, trickling, or nonstop refilling—and improve how smoothly the toilet operates.

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