How to Replace a Toilet Fill Valve

Step 1: Make sure the fill valve is the likely problem

1. Take the tank lid off and flush the toilet once.
2. Watch the refill cycle. A bad fill valve is a likely match if the tank refills very slowly, the valve hisses or chatters, the water level keeps rising too high, or the toilet keeps running because water never shuts off cleanly.
3. Check that the flapper is able to seal and that the chain is not holding it open. If the flapper is leaking, replacing the fill valve alone will not stop a constant run-on refill.
4. Look for obvious cracks in the tank, severe rust on hardware, or water dripping from the shutoff valve or supply line.

If it works: You have refill symptoms that point to the fill valve, and the tank and shutoff area look sound enough for a normal replacement.

If it doesn’t: If the toilet only runs because the flapper leaks or the chain is misadjusted, fix that first. If the shutoff valve will not close fully, plan to replace or repair that before changing the fill valve.

Step 2: Shut off the water and empty the tank

1. Turn the toilet shutoff valve clockwise until it stops.
2. Flush the toilet and hold the handle down to drain as much water from the tank as possible.
3. Use a sponge or towel to soak up the remaining water in the bottom of the tank.
4. Place a bucket or pan under the supply connection below the tank to catch drips.

If it doesn’t: If water keeps entering the tank after the shutoff is closed, the shutoff valve is not sealing and needs attention before this repair will stay dry.

Step 3: Remove the old fill valve

1. Unscrew the water supply line from the bottom of the fill valve shank under the tank.
2. Disconnect the small refill tube from the overflow tube inside the tank.
3. From underneath the tank, loosen and remove the fill valve locknut. Hold the valve body inside the tank if it wants to spin.
4. Lift the old fill valve straight up and out of the tank.
5. Wipe the tank opening clean so the new rubber seal can sit flat.

Step 4: Set the new fill valve and install it in the tank

1. Adjust the new fill valve height before installing it so the top of the valve will sit above the overflow tube and within the tank's usable height range.
2. Place the new seal or washer on the valve as directed by the part design, then insert the valve through the tank opening.
3. From underneath the tank, thread on the locknut and tighten it snugly. Do not overtighten plastic threads.
4. Attach the refill tube to the valve and clip the other end to the overflow tube so the tube points into the overflow without being shoved down inside it.

Step 5: Reconnect the water line and set the water level

1. Reconnect the supply line to the new fill valve shank and tighten it snugly without forcing the threads.
2. Slowly turn the shutoff valve back on while watching underneath the tank for leaks.
3. Let the tank fill completely.
4. Adjust the fill valve so the water level stops at the tank's marked water line or about 1 inch below the top of the overflow tube if no mark is visible.

Step 6: Flush several times and confirm the repair held

1. Flush the toilet at least three times in a row.
2. Listen for hissing, chattering, or a delayed shutoff after each refill.
3. Watch the bowl and tank for a few minutes after the last flush to make sure the water level stays stable and the toilet does not start refilling on its own.
4. Check once more under the tank for slow drips around the supply line and fill valve locknut.

If it works: The toilet refills normally, shuts off cleanly, and stays quiet and dry between flushes.

If it doesn’t: If the toilet still runs after the new fill valve is adjusted correctly, inspect the flapper, overflow height, and flush valve seal for the real cause.