Running toilet: what causes it and how to fix it
A toilet that keeps running, refills on its own every few minutes, or hisses in the middle of the night is wasting water every hour. The good news is that most running toilets come down to a few inexpensive parts inside the tank.
The usual causes
- Worn flapper. The rubber flapper at the bottom of the tank hardens or warps over time and stops sealing. Water leaks into the bowl, and the tank refills on its own ("phantom flushing").
- Chain too short or tangled. If the chain holds the flapper slightly open, the toilet never stops running.
- Fill valve set too high. If the water level rises above the overflow tube, it spills down the tube nonstop.
- Worn fill valve. An old fill valve can hiss, refill slowly, or fail to shut off.
- Cracked overflow tube or flush valve. Less common, and usually a bigger repair.
A two-minute test
- Take the tank lid off and set it somewhere safe (they break easily).
- Look at the water level. Is it above the top of the overflow tube? If so, the fill valve needs adjusting or replacing.
- Put a few drops of food colouring in the tank and wait 15 minutes without flushing. If colour shows up in the bowl, the flapper is leaking.
- Check that the chain has a little slack when the flapper is closed.
If you are not comfortable going further, close the shut-off valve behind the toilet (clockwise) to stop the water until it is fixed. If that valve won't turn or starts dripping, leave it and send us a photo.
Typical price ranges (published sources)
These are typical ranges from cost guides, not our prices:
| Job | Typical range | Source |
|---|---|---|
| Fix a toilet (Canada) | $200–$400 | HomeStars Canada cost guide |
| Toilet repair (Ottawa reviews) | average reported $344 | HomeStars Ottawa cost guide |
| Toilet installation (Canada) | $260–$683 | HomeStars Canada cost guide |
Sources: HomeStars Canada plumbing cost guide and HomeStars Ottawa plumbing cost guide, both updated Aug. 2026.
When it is more than a flapper
Some signs point to a bigger job:
- Water on the floor around the base (possibly a failed wax seal or a cracked bowl)
- Water dripping from the bolts under the tank
- A crack anywhere in the tank or bowl
- A very old toilet where replacement parts no longer fit well
In those cases, replacing the toilet can make more sense than repairing it, especially with an older high-volume model.
Why it's worth fixing soon
A constantly running toilet adds to your water and sewer bill every day. In rental units and condos, a running toilet is also one of the most common reasons for a surprise high bill. Property managers: if you have several units with the same model, one photo set can help price the parts for all of them.
Get a personal quote from photos
Send us:
- A photo inside the tank with the lid off
- A photo of the shut-off valve and supply line behind the toilet
- A short note on what you hear or see (hissing, refilling, water on the floor)
A licensed plumber reviews every request and replies with a personal quote. No automatic estimates and no obligation. This is a small pilot, so we can't promise a response time, and the form is not for emergencies.