Toilet Won't Stop Running: Complete Fix Guide

Diagnose the Problem

Is water going into the overflow tube?

• Yes → Float is set too high or fill valve is faulty
• No → Flapper is leaking or chain is too tight

What You’ll Need

Fix 1: Adjust the Float

The float controls the water level in your toilet tank. If it’s set too high, water will continuously flow into the overflow tube, causing the toilet to run.

Step 1: Remove the Tank Lid

Carefully lift the ceramic lid off your toilet tank and set it aside on a protected surface. This exposes the internal components.

Step 2: Identify the Float Mechanism

Locate the float, which is typically a ball on an arm or a cylinder that slides up and down the fill valve shaft. This component rises with the water level.

Step 3: Adjust the Water Level

For ball floats, gently bend the float arm downwards. For cylinder floats, pinch the clip on the side of the fill valve shaft and slide the float down. Aim for the water level to be about 1 inch below the top of the overflow tube.

Step 4: Flush and Observe

Flush the toilet and watch the tank refill. Ensure the water stops filling when it reaches the new, lower level, without overflowing into the tube.

Fix 2: Inspect and Replace the Flapper

The flapper creates a watertight seal at the bottom of the tank, holding water until you flush. A worn or misaligned flapper is a very common cause of running toilets.

Step 1: Turn Off Water Supply

Find the shut-off valve on the wall behind the toilet, usually near the floor. Turn it clockwise until the water flow completely stops. Flush the toilet to empty the tank.

Step 2: Disconnect the Flapper Chain

Locate the chain connecting the flush handle to the flapper. Unhook it from the flush handle lever, noting how it was attached to ensure proper reinstallation.

Step 3: Remove the Old Flapper

Unseat the flapper from the flush valve drain opening. Most flappers have “ears” that slide onto posts on either side of the flush valve. Gently pull them off the posts.

Step 4: Install the New Flapper

Slide the ears of the new flapper onto the posts of the flush valve. Make sure it sits flat and creates a good seal over the drain opening. Reattach the flapper chain to the flush handle lever, ensuring there is only a small amount of slack (about 1/2 inch) when the flapper is closed.

Step 5: Restore Water and Test

Turn the water supply back on by rotating the shut-off valve counter-clockwise. Allow the tank to refill completely, then flush the toilet several times to confirm the new flapper seals properly and the toilet stops running.

Fix 3: Replace the Fill Valve

If adjusting the float and replacing the flapper don’t resolve the running, the fill valve itself may be faulty and continuously allow water into the tank.

Step 1: Turn Off Water and Empty Tank

Turn off the water supply valve and flush the toilet to drain all water from the tank. Use a sponge to remove any remaining water in the bottom of the tank.

Step 2: Disconnect Water Supply Line

Unscrew the water supply line from the bottom of the fill valve using pliers. Have a towel ready for any drips. Hold the fill valve stem inside the tank to prevent it from turning.

Step 3: Remove Old Fill Valve

Underneath the tank, unscrew the large nut that secures the fill valve to the tank. Once the nut is removed, lift the old fill valve straight out of the tank from the inside.

Step 4: Install New Fill Valve

Insert the new fill valve into the hole at the bottom of the tank. Ensure the rubber washer is correctly positioned on the shank inside the tank. Secure it from underneath with the large retaining nut, hand-tightening first, then a quarter-turn with pliers.

Step 5: Reconnect Water Line and Adjust

Reconnect the water supply line to the new fill valve, hand-tightening it first, then a quarter-turn with pliers. Turn on the water supply and check for leaks. Adjust the float on the new fill valve as per “Fix 1” to set the proper water level.

When to Call a Pro

Call a plumber if you’ve followed these steps and the toilet still runs, or if you notice water leaking from the base of the toilet (which could indicate a wax ring issue). Complex leaks involving cracked tanks or bowls, or if you’re uncomfortable working with plumbing, also warrant professional help. A professional can quickly diagnose and fix issues that are beyond basic DIY repair.

FAQ

How much water does a running toilet waste? A continuously running toilet can waste hundreds to thousands of gallons of water per day, significantly increasing your water bill. Even a small, silent leak can add up to over 6,000 gallons per month.

Why does my toilet run intermittently? Intermittent running, or “ghost flushing,” often indicates a slow leak, most commonly from a flapper that isn’t sealing perfectly. Water slowly drains, causing the tank to refill periodically. This can also be caused by a faulty fill valve.

Can a running toilet cause damage? While a running toilet primarily wastes water, a persistent leak could eventually contribute to rot or mold if water escapes the tank or bowl and isn’t noticed. It also puts continuous strain on your plumbing system.

How can I tell if my flapper is leaking? Add a few drops of food coloring to your toilet tank. Do not flush. Wait 15-20 minutes. If the colored water appears in the toilet bowl without flushing, your flapper is leaking and needs replacement.