A toilet that keeps running is usually caused by a faulty, misaligned, or dirty flapper that fails to create a proper seal, allowing water to leak from the tank into the bowl. Other common causes include an improperly adjusted float, a chain that is too long or tangled, or a malfunctioning fill valve.
If your toilet keeps running long after you flush, you are not alone. A running toilet is one of the most common plumbing problems homeowners face, and in most cases it is simple and inexpensive to fix. A constantly running toilet is usually caused by a worn flapper, an improperly adjusted float, or a failing fill valve. In this guide, you will learn exactly why your toilet keeps running, how to diagnose the issue, and step by step instructions to fix it yourself and when you should call a professional plumber.
Why You Should Fix a Running Toilet Quickly
A running toilet might seem like a small annoyance, but it can waste a surprising amount of water. Even a slow, silent leak can send hundreds of gallons of clean water down the drain every day.
Here is why you should not ignore the problem:
- Higher monthly water bills
- Wasted water and environmental impact
- Increased wear on toilet components
- Risk of internal damage inside the tank
A continuously running toilet can waste between 200 and 500 gallons of water per day depending on the severity of the leak. Over the course of a month, that could mean thousands of gallons of unnecessary water use.
The good news is that most repairs cost less than twenty dollars and take under thirty minutes.
How a Toilet Works (Quick Overview)
Before you fix the problem, it helps to understand how your toilet functions.
Inside your toilet tank are several key components:
- Flapper
- Flush valve
- Fill valve
- Float
- Overflow tube
- Chain and handle
When you press the handle, the chain lifts the flapper. Water rushes from the tank into the bowl. Once the tank empties to a certain level, the flapper falls back into place and seals the opening. The fill valve then refills the tank with water. As the water rises, the float rises with it. When the water reaches the correct level, the float tells the fill valve to shut off.
If any part of that process fails, the toilet continues to run.
1. The Flapper Isn’t Sealing Properly (Most Common Cause)
This is the most common reason toilets run continuously. The flapper is a rubber valve at the bottom of the tank. Over time, it can:
- Warp
- Crack
- Become brittle
- Accumulate mineral buildup
- Lose flexibility
If the flapper does not create a tight seal, water slowly leaks from the tank into the bowl. When the tank water level drops, the fill valve activates to refill it. This cycle continues indefinitely.
How to Check the Flapper
- Remove the toilet tank lid.
- Flush the toilet and watch the flapper.
- After it closes, look for water trickling into the bowl.
- If you hear water running and the tank water level slowly drops, the flapper is likely leaking.
How to Replace the Flapper
- Turn off the water supply valve behind the toilet.
- Flush to empty most of the tank.
- Disconnect the chain from the flush lever.
- Unhook the flapper from the overflow tube.
- Install the new flapper in the same position.
- Reattach the chain with slight slack.
Flappers typically cost between five and fifteen dollars. Make sure you bring the old one to the hardware store to find a compatible match.
2. The Chain Is Too Tight or Too Loose
The chain connecting the flush handle to the flapper must have a small amount of slack. If the chain is too tight, it can prevent the flapper from fully closing.
If it is too loose, it can get stuck under the flapper. Either issue can cause water to leak continuously.
How to Adjust the Chain
- Remove the tank lid.
- Inspect the chain length.
- Adjust it so there is about half an inch of slack.
- Ensure it does not catch under the flapper.
This quick adjustment can immediately solve the issue in many cases.
3. The Float Is Set Too High
If your toilet constantly sounds like it is refilling, the water level may be too high. When the float is set too high, water spills into the overflow tube. This causes the fill valve to continue adding water.
There are two common types of floats.
Ball Float
Older toilets have a large plastic or metal ball attached to a metal arm.
To adjust it:
- Gently bend the metal arm downward to lower the water level.
Cup Float
Newer toilets use a cylindrical float that slides up and down the fill valve.
To adjust it:
- Locate the adjustment screw on the fill valve.
- Turn the screw clockwise to lower the water level.
- The correct water level should sit about one inch below the top of the overflow tube.
4. The Fill Valve Is Worn Out
If adjusting the float does not fix the problem, your fill valve may be worn out.
Signs of a bad fill valve include:
- Hissing sounds
- Slow tank refill
- Water that never fully shuts off
- Intermittent refilling
Fill valves wear out over time due to mineral buildup and normal use.
How to Replace a Fill Valve
- Turn off the water supply.
- Flush the toilet and sponge out remaining water.
- Disconnect the water supply line under the tank.
- Unscrew the locknut holding the fill valve in place.
- Remove the old fill valve.
- Insert the new valve and secure it.
- Reconnect the water supply line.
- Turn the water back on and test.
Most fill valves cost between ten and twenty five dollars and are beginner friendly to install.
5. The Overflow Tube Is Cracked
If water continuously flows into the overflow tube, there may be a crack in the tube or an issue with the flush valve assembly.
In some cases, the entire flush valve assembly must be replaced. This requires removing the tank from the bowl.
If you are not comfortable disconnecting the tank bolts and handling internal seals, it may be best to contact a plumber.
How to Test for a Silent Leak
Sometimes a toilet runs quietly and you do not notice it.
Here is a simple dye test:
- Add several drops of food coloring to the tank water.
- Wait fifteen to twenty minutes.
- Check the toilet bowl without flushing.
If colored water appears in the bowl, the flapper is leaking.
This simple test can help you catch water waste early.
When to Call a Plumber
Most running toilet issues can be fixed with a simple flapper or fill valve replacement, but there are situations where calling a professional is the smartest choice. If you have replaced the flapper, adjusted the float, and even installed a new fill valve and the toilet still will not stop running, there may be a deeper issue inside the flush valve assembly or with the tank itself. Cracks in the tank, persistent leaks around the base of the toilet, or water pooling on the floor are signs that the problem goes beyond a basic DIY repair.
You should also contact a plumber if the shut off valve behind the toilet does not fully stop the water flow, or if the toilet needs to be removed to replace internal components. Working with tank bolts, seals, and wax rings can be messy and sometimes lead to accidental water damage if not handled correctly. A licensed plumber can quickly diagnose the issue, make the proper repair, and ensure everything is sealed and functioning properly so you do not have to worry about ongoing leaks or hidden damage.
Preventing Future Toilet Problems
Preventing a running toilet starts with simple, routine maintenance. Once or twice a year, remove the tank lid and inspect the internal components. Look for signs of wear on the flapper, corrosion on the chain, mineral buildup on the fill valve, or water levels that sit too high. Catching these small issues early can prevent continuous leaks and unexpected spikes in your water bill. It is also a good idea to test for silent leaks occasionally by using the food coloring method to ensure the flapper is sealing properly.
Avoid using chemical drop in tank cleaners, as they can break down rubber seals and shorten the lifespan of internal parts. If you live in an area with hard water, mineral deposits can accumulate more quickly, so periodic cleaning of tank components can help extend their life. Replacing the flapper every few years as preventative maintenance is inexpensive and can stop problems before they start. A few minutes of inspection each year can save you from larger repairs and wasted water down the line.
Final Thoughts About Fixing Running Toilets
Fixing a running toilet may seem intimidating at first, but in most cases it is one of the easiest plumbing repairs you can handle as a homeowner. The majority of issues come down to a worn flapper, an improperly adjusted float, or a failing fill valve. Taking the time to address it quickly prevents wasted water, reduces your utility bill, and protects your bathroom from potential long term damage.
The key is to approach the repair step by step. Start with the simplest fixes and work your way through the common causes before assuming it is a major issue. If you ever feel unsure or discover signs of leaks outside the tank, do not hesitate to contact a licensed plumber for help. Whether you handle the repair yourself or call in a professional, resolving a running toilet promptly ensures your plumbing system stays efficient, quiet, and reliable.
If your toilet will not stop running, Iron Mountain Plumbing can quickly diagnose the issue and provide reliable repairs to restore efficiency and prevent wasted water in your home.
Frequently Asked Questions About Toiler Repair
Why does my toilet keep running after I flush?
A toilet usually keeps running because water is leaking from the tank into the bowl. The most common cause is a worn or warped flapper that no longer creates a tight seal. When water slowly escapes through the flush valve opening, the tank level drops and triggers the fill valve to refill it. This cycle can continue indefinitely. Other possible causes include a misadjusted float, a faulty fill valve that will not shut off completely, or a chain that is preventing the flapper from closing properly. Identifying which component is failing is the first step toward fixing the problem.
How much water can a running toilet waste?
A running toilet can waste anywhere from 200 to 500 gallons of water per day depending on the severity of the leak. Over the course of a month, that can add up to thousands of gallons and significantly increase your water bill. Even a small, silent leak inside the tank can cost you more than you realize. Because toilets account for a large portion of indoor water usage, addressing a continuous running issue promptly can result in noticeable savings on your utility costs.
Why does my toilet randomly start running hours after I flush?
If your toilet seems to refill at random times, it is usually due to a slow internal leak. Water gradually escapes from the tank into the bowl through a worn flapper or improperly seated seal. Once the water level drops enough, the float activates the fill valve to refill the tank. This can happen even hours after the last flush. Because the leak may be slow and silent, many homeowners do not notice it until they hear the tank refilling unexpectedly.