A constantly running toilet can be both annoying and costly, wasting gallons of water daily and increasing utility bills. Fortunately, most causes of a running toilet are easy to diagnose and fix with a bit of know-how. We’ll explore five common reasons why your toilet keeps running and provide DIY solutions to stop the water flow.
1. Faulty Flapper Valve

Cause: The flapper valve is a rubber seal that controls water flow from the tank to the bowl. If it becomes worn, warped, or dirty, it may not close properly, causing the toilet to run continuously.
Solution:
Inspect the Flapper: Open the toilet tank and check if the flapper is sealing the flush valve properly.
Clean the Flapper: If it’s dirty, gently clean it with a sponge and warm water.
Replace the Flapper: If the flapper is damaged or misshapen, replace it with a compatible model.
2. Float Position Is Too High
Cause: The float in the tank controls the water level. If the float is set too high, water will keep flowing into the overflow tube, causing the toilet to run.
Solution:
Adjust the Float: If your toilet has a float arm, bend it slightly downward. For newer toilets with a float cup, adjust the height using the adjustment screw on the fill valve.
Check for Water Level Markings: Look inside the tank for a water level mark, typically about an inch below the top of the overflow tube. Adjust the float to align with this mark.
Test the Adjustment: Flush the toilet after making adjustments to ensure the water level stops at the correct point. If issues persist, consider replacing the float mechanism.
3. Worn-Out Fill Valve

Cause: The fill valve refills the toilet tank after each flush. If it’s worn or damaged, it may fail to shut off, causing constant water flow.
Solution:
Inspect the Fill Valve: Listen for hissing sounds, indicating a faulty valve.
Replace the Fill Valve: Turn off the water supply, drain the tank (by flushing the toilet) and install a new fill valve according to the manufacturer’s instructions.
4. Chain Issues
Cause: The chain connecting the flush handle to the flapper can cause problems if it’s too short or too long.
Solution:
Adjust the Chain Length: If the chain is too tight, it may prevent the flapper from sealing. If it’s too loose, the flapper might not lift properly during a flush. Adjust the chain to ensure a slight slack.
5. Leaky Flush Valve or Overflow Tube

Cause: A cracked flush valve or improperly seated overflow tube can cause water to leak into the toilet bowl.
Solution:
Inspect the Flush Valve: Look for cracks or damage.
Replace the Flush Valve: If damaged, replace it with a compatible part.
Preventive Tips to Avoid a Running Toilet
Regular Maintenance: Inspect toilet components every few months to catch wear and tear early.
Avoid Harsh Cleaners: Use gentle cleaning products to prevent damage to rubber and plastic parts.
Replace Parts When Needed: Don’t wait until a small issue turns into a costly repair.
When to Call a Plumber

While most running toilet issues can be resolved with DIY efforts, you should call a plumber if:
The toilet continues to run after trying the above fixes.
You notice water damage around the toilet base.
You’re uncomfortable performing the repairs yourself.
By understanding these common causes and applying the right fixes, you can prevent a running toilet from draining your wallet and ensure your plumbing system runs efficiently. Regular inspections and timely maintenance can save you from costly water bills and unexpected plumbing emergencies.
The Great Plumbing Co.
For nearly three decades, The Great Plumbing Co. has been providing exceptional plumbing services for homeowners as well as business owners throughout Toronto and the GTA. Whether you’re dealing with a leaky hose bib, a clogged drain, or a toilet repair and service you can trust The Great Plumbing Co. to deliver timely solutions tailored to your specific requirements.
Contact us or book online to schedule your residential plumbing appointment.