Why Does My Drain Keep Clogging? Causes and Fixes
Understand the common reasons drains clog again and again, and learn when professional drain cleaning is the right solution.
Read More →That steady hiss is wasting hundreds of gallons of water a month. Here's how to diagnose and fix a running toilet yourself.
A running toilet is one of the most common plumbing problems in American homes, and it is also one of the most wasteful. A toilet that runs continuously can waste anywhere from 200 to 30,000 gallons of water every month, depending on the severity of the leak. That wasted water shows up directly on your utility bill, sometimes adding $50 or more to your monthly costs.
The good news is that most running toilet repairs are simple, inexpensive, and well within the reach of a careful homeowner. In most cases, the fix takes less than an hour and costs less than $20 in parts. In this guide, we'll walk through the most common causes of a running toilet, how to diagnose them, and how to fix them step by step.
A toilet runs when water leaks from the tank into the bowl (past the flapper), or when the fill valve fails to shut off once the tank is full. Understanding which of these is happening is the first step toward a fix. Here are the most common culprits:
Start by removing the tank lid and watching the mechanism during and after a flush. You'll usually spot the problem within a minute or two. If the water keeps trickling into the bowl, the flapper is the likely culprit. If the tank keeps refilling and water pours down the overflow tube, the fill valve or water level is the issue.
The flapper is a rubber seal at the bottom of the tank that lifts when you flush and drops back down to hold water. Over time, heat, chlorine, and hard water cause it to warp, harden, or crack. A failing flapper is responsible for the majority of running toilets.
If your water is hard, also clean the flush valve seat with fine sandpaper or a cloth and vinegar to remove mineral deposits that prevent a seal. You can read more about how minerals affect your plumbing in our guide to understanding hard water.
If your toilet keeps refilling and water spills down the overflow tube, the fill valve is not shutting off. Fill valves are simple mechanical devices, and many can be fixed by adjusting them or cleaning the inlet. If the valve is worn out, a replacement kit costs about $15 to $25 and takes roughly 30 minutes to install.
Adjust the water level first. Most modern fill valves have an adjustment screw or a rotating collar on the top. Set the water level so it sits about one inch below the top of the overflow tube. If the valve still runs, shut off the water, disconnect the supply line, and clean any debris from the valve inlet. When cleaning doesn't help, replace the valve entirely — a new valve with fresh seals will eliminate the problem for years.
Always turn off the water supply before working on any part of the tank, and inspect the supply line for cracks while you have it disconnected. A brittle supply line is a common cause of unexpected water damage, so replace it if it shows any signs of wear.
Before calling a plumber, work through these quick checks. Each takes just a few minutes and covers the remaining common causes of a running toilet:
If the toilet still runs after these steps, the problem may be internal — such as a cracked tank, a bad tank-to-bowl gasket, or a corroded flush valve assembly. At that point, professional help is the safest route. A plumber can also spot problems you can't see, like stress cracks that could eventually flood your bathroom floor.
At EliteHomePlumbers, we connect homeowners with licensed plumbing professionals who handle toilet repairs, drain issues, fixture installation, and more. Our network provides:
Whether you need a simple repair or a full bathroom renovation, we can match you with a trusted professional near you. Explore our plumbing services or find a plumber in your area on our locations page.
Understand the common reasons drains clog again and again, and learn when professional drain cleaning is the right solution.
Read More →Essential maintenance tips to keep your water heater running efficiently and extend its lifespan.
Read More →Quick action during a plumbing emergency can prevent serious water damage while you wait for help.
Read More →