Step-by-step fix
Step 1: Shut off the water and empty the tank
- Turn the toilet shutoff valve clockwise until it stops.
- Flush the toilet and hold the handle down to drain as much water from the tank as possible.
- Use a sponge or towel to remove the small amount of water left in the bottom of the tank.
- Place a bucket or container under the supply connection below the tank.
If it works: The tank is mostly empty and no more water is entering it.
If it doesn’t: If the tank keeps refilling, the shutoff valve may not be closing fully. Try closing it gently again. If water still flows steadily, stop and address the shutoff valve before replacing the fill valve.
Stop if:- The shutoff valve will not close and water continues entering the tank.
- The shutoff valve or supply line starts leaking when touched.
Step 2: Disconnect the supply line and remove the old fill valve
- Unscrew the water supply line from the bottom of the fill valve shank under the tank.
- Loosen and remove the plastic or metal locknut holding the fill valve to the tank.
- From inside the tank, lift the old fill valve straight up and out.
- Remove the old refill tube from the overflow tube if it is still attached.
If it works: The old fill valve is out and the tank opening is clear.
If it doesn’t: If the locknut is stuck, use pliers or a wrench for gentle extra leverage. Do not twist hard enough to crack the tank.
Stop if:- The tank flexes or makes cracking sounds while you loosen the nut.
- The supply line or tank fitting is heavily corroded and will not loosen safely.
Step 3: Prepare the new fill valve
- Compare the new fill valve to the old one to confirm the shank size and overall height are similar.
- Adjust the new valve height if the design allows it so the top of the valve will sit above the overflow tube once installed.
- Make sure any rubber washer provided with the new valve is positioned as directed for the tank opening.
- Attach the refill tube to the new valve if the kit requires it before installation.
If it works: The new fill valve is adjusted to a reasonable height and ready to install.
If it doesn’t: If the new valve does not match the opening, connection, or tank space, do not force it. Recheck the replacement part before continuing.
Stop if:- The new valve does not fit the tank opening or supply connection.
- The valve body is too tall or too wide to sit correctly in the tank.
Step 4: Install and secure the new fill valve
- Insert the new fill valve into the tank opening with the float and body clear of the flush valve and tank walls.
- From under the tank, thread the locknut onto the fill valve shank and tighten it until snug.
- Hold the valve so it stays upright while tightening, but do not overtighten.
- Clip or place the refill tube onto the overflow tube so the tube sends water into the overflow without being pushed down inside it.
If it works: The new fill valve is secure, upright, and the refill tube is positioned correctly.
If it doesn’t: If the valve shifts or leans, loosen the nut, reposition the valve, and retighten. If the refill tube is too long, trim it so it fits neatly.
Stop if:- The locknut will not tighten evenly or the valve will not sit flat.
- The refill tube cannot be routed without kinking or being forced into the overflow tube.
Step 5: Reconnect the water and check for leaks
- Reconnect the supply line to the bottom of the new fill valve and tighten it snugly.
- Slowly turn the shutoff valve counterclockwise to restore water.
- Watch under the tank and around the fill valve opening as the tank fills.
- If you see a small drip, shut the water back off and tighten the leaking connection slightly.
If it works: The tank fills and there are no leaks at the supply line or fill valve connection.
If it doesn’t: If leaking continues after a small retightening, shut the water off and inspect the washer, nut alignment, and supply connection for cross-threading or a poor seal.
Stop if:- Water leaks steadily from under the tank after retightening.
- The shutoff valve itself begins leaking when reopened.
Step 6: Set the water level and test the flush
- Let the tank fill completely and note where the water stops.
- Adjust the fill valve so the water level sits below the top of the overflow tube and near the marked fill line if the tank has one.
- Flush the toilet several times to confirm the tank refills properly and the water shuts off cleanly.
- Listen for continued running or hissing after the tank is full.
If it works: The toilet flushes normally, refills to the correct level, and stops running when full.
If it doesn’t: If the toilet keeps running, recheck the water level, refill tube placement, and the flapper or flush seal. A separate flush valve or flapper issue may also be present.
Stop if:- Water rises into the overflow tube and will not stop.
- The toilet still runs continuously after basic adjustment.
Replacement Parts
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FAQ
Do I need to replace the supply line too?
Not always. If the supply line is in good shape and reconnects without leaking, you can usually reuse it. Replace it if it is old, kinked, corroded, or drips after reconnection.
Why is my toilet still running after I replaced the fill valve?
The water level may be set too high, the refill tube may be placed incorrectly, or the flapper or flush seal may also be leaking. Check those items before replacing more parts.
How tight should the fill valve locknut be?
Tight enough to hold the valve securely and prevent leaks, but not so tight that you stress the porcelain tank. Snug plus a small additional turn is usually enough.
Can I replace a toilet fill valve without turning off the house water?
Usually yes, if the toilet's local shutoff valve works properly. If that valve does not fully close, you may need to shut off water to the home before continuing.
What if the old locknut will not come off?
Try steady pressure with pliers or a wrench while supporting the valve. If corrosion is severe or the tank starts flexing, stop rather than risk cracking the tank.