How to Fix a Running Toilet Without Calling a Plumber

Why You Should Not Ignore a Running Toilet

A toilet that runs continuously can waste 200 gallons of water per day -- that is over 6,000 gallons per month. Even an intermittent run (the kind that cycles on and off every few minutes) can waste 1,000 gallons monthly. Beyond the water bill, the constant flow puts unnecessary wear on the fill valve and other tank components. And if others in the house have noticed the shower pressure drops when someone flushes, a constantly running toilet makes that worse too.

The good news is that this is one of the most straightforward home repairs you can do. You do not need a plumber, you do not need special tools, and the parts cost a few dollars at any hardware store.

Understanding What Is Inside Your Toilet Tank

Lift the tank lid and look inside. You will see a few key components:

• Flapper -- the rubber seal at the bottom of the tank that lifts when you flush and drops back down to stop water from flowing into the bowl.
• Fill valve -- the tall mechanism (usually on the left side) that refills the tank after a flush. It is connected to the water supply line.
• Overflow tube -- the open pipe in the center of the tank. If the water level gets too high, excess water flows down this tube into the bowl to prevent flooding.
• Float -- either a ball on an arm or a cup that rides up and down the fill valve. It tells the fill valve when to stop filling.

Step 1: Diagnose the Problem

Before replacing anything, figure out which component is failing.

Fix 1: Replace the Flapper

This is the most common cause of a running toilet and the easiest fix.

The flapper is a rubber or silicone seal that deteriorates over time. Hard water, chlorine in municipal water, and simple age cause it to warp, crack, or lose its flexibility. When the flapper no longer creates a watertight seal, water slowly leaks from the tank into the bowl, triggering the fill valve to run periodically.

What you need: A replacement flapper ($3 to $8 at any hardware store). Universal flappers fit most toilets, but bring your old one to the store to match the size if you are unsure.

How to do it:

1. Shut off the water supply valve behind the toilet.
2. Flush the toilet to empty the tank.
3. Unhook the old flapper from the overflow tube ears (the small pegs on either side of the tube) and disconnect the chain from the flush lever.
4. Hook the new flapper onto the same ears and reconnect the chain. Leave about half an inch of slack in the chain -- enough that the flapper sits flat but the chain is not tight.
5. Turn the water back on and let the tank fill.
6. Flush once and watch. The flapper should drop cleanly and stop all water flow into the bowl.

Fix 2: Adjust the Float Level

If water is flowing into the overflow tube, the fix is usually a simple adjustment rather than a replacement.

For ball-and-arm floats (the round ball on a metal arm): Bend the arm slightly downward. This lowers the point at which the float tells the fill valve to stop. The goal is a water level about 1 inch below the top of the overflow tube.

For cup-style floats (a cylinder that slides up and down the fill valve): Look for an adjustment clip or screw on the float. Squeeze the clip and slide the float down the rod, or turn the adjustment screw counterclockwise to lower the float position.

After adjusting, flush the toilet and confirm that the water stops filling at the correct level and does not reach the overflow tube.

Fix 3: Replace the Fill Valve

If the fill valve hisses, runs continuously, or does not shut off even when the float is at the correct level, the valve itself is worn out and needs replacement.

How to replace a fill valve:

1. Shut off the water supply and flush to empty the tank. Sponge out remaining water.
2. Place a towel under the tank. Disconnect the water supply line from the bottom of the fill valve (use pliers if hand-tight does not work).
3. Remove the lock nut on the underside of the tank that holds the fill valve in place. Lift the old valve out.
4. Adjust the height of the new fill valve so the top is at least 1 inch above the overflow tube (most valves are adjustable by twisting).
5. Insert the new valve through the tank hole, hand-tighten the lock nut underneath, and reconnect the water supply line.
6. Attach the refill tube to the overflow tube (it clips on) and turn the water back on.
7. Adjust the float to set the correct water level.

The entire process takes about 15 to 20 minutes and requires no specialized tools beyond pliers.

When Something Else Is Going On

In rare cases, the problem is not the flapper, float, or fill valve.

Cracked overflow tube. If the overflow tube itself is cracked below the waterline, water will leak into the bowl continuously. The overflow tube is part of the flush valve assembly, which is a bigger replacement job. This is one situation where calling a plumber may be worthwhile unless you are comfortable removing the tank.

Warped tank-to-bowl gasket. The large rubber gasket between the tank and the bowl can deteriorate and allow water to leak externally. You will notice water on the floor around the toilet base. Replacement requires removing the tank, which adds complexity.

Related: Why Does the Shower Pressure Drop When Someone Flushes? · Why Does My Drain Smell Like Rotten Eggs? · Garbage Disposal Humming But Not Spinning