How to Fix a Running Toilet
A running toilet is almost always caused by a worn-out rubber flapper, an improper chain length, or a faulty fill valve. You can fix most of these issues yourself in under 20 minutes with inexpensive parts from the hardware store.
Diagnose the Problem
Before replacing parts, take off the tank lid and observe the mechanics while you flush to see exactly where the failure is occurring.
- Check if the rubber flapper is sealing completely over the drain hole at the bottom.
- Look at the water level; if it's pouring into the overflow tube, the fill valve is the issue.
- Ensure the chain isn't tangled or caught under the flapper.
Adjust or Replace the Chain
If the chain connecting the flush handle to the flapper is too short, the flapper can't close. If it's too long, it can get trapped under the flapper seal.
- Unhook the chain and adjust the clip so there is only a small amount of slack.
- Trim excess chain with pliers so it doesn't interfere with the seal.
- Test the flush to ensure the flapper lifts properly and seats firmly.
Replace a Leaky Flapper
Over time, rubber flappers warp or degrade due to chlorine in the water, causing a silent, continuous leak into the bowl.
- Shut off the water supply valve behind the toilet and flush to empty the tank.
- Unhook the old flapper from the overflow tube pegs and pull it out.
- Snap a new, correctly sized flapper into place and reattach the chain.
Adjust the Fill Valve
If water is continuously spilling into the vertical overflow tube, the float is set too high, telling the fill valve to keep adding water.
- Locate the adjustment screw on top of the fill valve or the clip on the float rod.
- Turn the screw counterclockwise to lower the float level.
- The water should stop filling about one inch below the top of the overflow tube.
When to Call a Professional
Call a plumber if replacing the flapper and fill valve doesn't stop the running, or if the toilet is leaking water onto the floor around the base.
What a Plumber Will Do
A plumber will rebuild the entire tank internals, replace a worn flush valve seat, or pull and reset the toilet with a new wax ring if it is leaking at the base.
Frequently Asked Questions
How much water does a running toilet waste?
A constantly running toilet can waste over 200 gallons of water per day, resulting in a significant spike in your water bill.
Do I need tools to fix a running toilet?
Most toilet tank repairs require no tools at all, though a pair of pliers can be helpful for adjusting the chain or removing stubborn parts.
What if replacing the flapper doesn't work?
If a new flapper doesn't solve the leak, the flush valve seat (the rim the flapper sits on) may be corroded or chipped, requiring a full flush valve replacement.
Why does my toilet randomly run for a few seconds?
This is called "phantom flushing," caused by a very slow leak at the flapper. The fill valve briefly turns on to refill the lost water.