How to Fix a Running Toilet

A running toilet might not seem like a major issue at first, but it can waste hundreds of gallons of water each day and cause your utility bills to spike. Fortunately, you don’t need to call a plumber right away most toilet issues can be fixed with a few basic tools and a little patience. If your toilet won’t stop running, this guide will walk you through how to fix a running toilet step-by-step, helping you save water, money, and frustration.

Why Is a Running Toilet a Problem?

When a toilet continues to run after flushing, it usually means one or more components inside the tank are malfunctioning. While it might sound like a small nuisance, a constantly running toilet can:

• Waste over 200 gallons of water per day

• Increase your water bill significantly

• Lead to long-term wear or internal tank damage

The good news? Most running toilet repairs are simple and inexpensive. With a little know-how, you can fix the issue yourself often in under an hour.

Tools and Supplies You Might Need

Before you begin, gather a few basic tools and materials. Here’s what you might need to fix a running toilet:

• Adjustable wrench

• Rubber gloves

• Sponge or towel (to soak up water)

• Replacement toilet parts (flapper, fill valve, float)

• Bucket (optional)

• Flashlight (to inspect inside the tank)

You can find most of these items at a local hardware store or online, often bundled as toilet repair kits.

How a Toilet Works (Quick Overview)

To understand how to fix a running toilet, it helps to know the basic parts inside the tank:

• Flapper: A rubber seal that lifts when you flush and lets water flow into the bowl.

• Fill Valve: Controls water flow into the tank and shuts off when it reaches the correct level.

• Float: Rises with the water level and signals the fill valve to stop.

• Overflow Tube: Prevents the tank from overfilling.

If any of these parts fail or become misaligned, water may continue to flow causing your toilet to run nonstop.

Guide to Fix a Running Toilet

Let’s go through the most common causes and how to fix them.

1. Check the Flapper

One of the most common reasons for a running toilet is a faulty flapper. Over time, the rubber can warp, crack, or become misaligned.

How to check it:

• Remove the tank lid and flush the toilet.

• Watch the flapper lift and fall back into place.

• Press down on the flapper with a stick or tool. If the toilet stops running, the flapper is likely the issue.

Fix:

• Turn off the water supply (located behind the toilet near the floor).

• Flush to drain the tank.

• Unhook the old flapper from the pegs on the overflow tube.

• Attach a new flapper and connect the chain to the flush lever arm.

• Turn the water back on and test the flush.

This simple running toilet repair often solves the problem immediately.

2. Inspect the Fill Valve

If water continues to run into the tank after replacing the flapper, the fill valve may be the issue.

How to inspect:

• Look for water constantly entering the tank from the supply line.

• If you hear hissing or see ripples on the water surface when the toilet isn’t being used, your fill valve may be stuck or misadjusted.

Fix:

• Turn off the water and drain the tank.

• Unscrew the old fill valve and replace it with a new one, following the product instructions.

• Reconnect the supply line and turn the water back on.

• Adjust the float height to ensure the tank stops filling at the correct level.

3. Adjust the Float

If the water level in your tank is too high, it may spill into the overflow tube, causing the toilet to keep running.

Types of floats:

• Ball float: Large plastic ball on a metal arm

• Cup float: Vertical cylinder attached to the valve body

How to adjust:

• For a ball float, gently bend the arm downward to lower the water level.

• For a cup float, turn the adjustment screw or clip to change the float’s height.

Adjust the float so the water level sits about 1 inch below the top of the overflow tube.

4. Examine the Overflow Tube

Even if your fill valve and flapper are working properly, a damaged or too-high overflow tube can cause water to constantly drain into the bowl.

What to do:

• Check if water is draining into the overflow tube.

• If the fill tube (a small hose) is inserted too far into the overflow tube, it can siphon water continuously.

Fix:

• Trim or reposition the fill tube so it’s clipped just above the top of the overflow tube—not inside it.

Final Test and Prevention Tips

Once you’ve completed the repairs:

1. Turn the water supply back on.

2. Let the tank fill.

3. Flush the toilet and watch carefully for leaks or unusual sounds.

4. Listen for the tank to refill and then stop completely.

If everything looks and sounds normal, congratulations you’ve successfully repaired your running toilet.

Prevention Tips:

• Check inside the tank every few months.

• Avoid using in-tank cleaning tablets, which can wear down rubber parts.

• Test for leaks by adding food coloring to the tank and waiting 15 minutes—if color appears in the bowl, the flapper may still be leaking.

When to Call a Plumber

While most running toilet issues can be fixed DIY, there are times when it’s best to call in a professional:

• If tank components are severely corroded or broken

• If the shutoff valve is stuck or leaking

• If you’ve replaced key parts and the toilet still won’t stop running

• If you’re unsure about local plumbing codes or complex internal repairs

A licensed plumber can identify deeper issues and ensure everything is up to code, especially if your plumbing system is older.

Conclusion

Knowing how to fix a running toilet is one of the most useful DIY skills a homeowner or renter can have. With just a few tools and a little time, you can resolve a frustrating problem, avoid costly water bills, and gain confidence in your ability to tackle home repairs.