How to Fix a Running Toilet
A running toilet usually comes down to the flapper or the fill valve. Here is how to find the cause and stop the water waste.
Last updated:
- Time
- Often 15–30 minutes
- Difficulty
- Easy to moderate
- You need
- Food coloring, rag, replacement parts
A running toilet is usually caused by a worn flapper that no longer seals or a fill valve that will not shut off. Before buying parts, shut off the water supply and check the water level and flapper first.
Start at the shut-off valve
Turn the small valve behind the toilet clockwise to shut off the water. Flush once to empty the tank. This makes the repair calmer and prevents overflows.
Find the cause
- Water level: if it is above the overflow tube, the fill valve is letting in too much water.
- Flapper test: add a few drops of food coloring to the tank, wait 15 minutes without flushing, and check the bowl. Color in the bowl means the flapper is leaking.
- Flapper condition: look for warping, mineral buildup, or a chain that is too tight or tangled.
- Fill valve: if the tank keeps filling or makes noise after it should stop, the fill valve or float is likely faulty.
Common fixes
- Adjust the water level so it sits below the overflow tube.
- Clean or replace a flapper that is warped or coated with minerals.
- Reposition or shorten a chain that is catching.
- Replace the fill valve if it will not shut off.
Replacement parts are inexpensive and widely available. Take a photo of the inside of the tank or the old part to the store to match it.
When to call a plumber
- The tank, bowl, or supply line is cracked.
- Water is leaking at the base of the toilet, which can mean a failed wax ring or flange.
- The shut-off valve will not close or is frozen.
- A repair you tried keeps failing.
Sources and assumptions
This guide covers common residential toilet designs. Models vary, so follow the manufacturer's instructions for your toilet.
Frequently asked questions
- Why does my toilet keep running after I flush?
- The most common cause is a flapper that no longer seals, letting water leak from the tank into the bowl so the fill valve keeps running. A stuck float or faulty fill valve can also be the cause.
- Does a running toilet waste a lot of water?
- Yes. A constantly running toilet can waste a large amount of water over time and raise your bill. Fixing it is usually inexpensive and worth doing promptly.
- How do I know if I need a new flapper?
- If the flapper looks warped, cracked, or coated with minerals, or if the dye test shows water leaking into the bowl, replace it. Flappers are inexpensive and simple to swap.