If your toilet still runs after replacing the flapper and adjusting the chain, the problem is usually deeper inside the tank. In these cases, the toilet may appear to work normally but continues refilling periodically or produces a constant trickling sound.
When the common fixes don’t solve the problem, the cause is often a worn fill valve, a damaged flush valve seat, or an issue with the tank water level. Fortunately, these problems are still usually inexpensive to repair.
Quick Answer
If a toilet keeps running even after replacing the flapper, the most likely causes are a faulty fill valve, a damaged flush valve seat, or tank water that rises into the overflow tube. Inspect and adjust the overflow tube and fill valve first, then check the flush valve assembly.
Signs the Problem Is Not the Flapper
If the flapper has already been replaced, look for these clues:
The tank refills periodically without being flushed
Tank water flows into the overflow tube
The fill valve cycles on and off
The tank water level slowly drops
The toilet runs randomly throughout the day
These symptoms usually point to a fill valve or flush valve problem rather than the flapper.
Step-by-Step: What to Check Next
1. Check Whether Water Is Entering the Overflow Tube
Remove the tank lid and watch the water level after the toilet refills.
Water should stop about ½ inch below the top of the overflow tube.
If water spills into the tube, the fill valve is allowing too much water into the tank.
Fix: Adjust the float downward until the water stops below the overflow tube.
See: Toilet Bowl Water Level Too High or Too Low: How to Fix It
2. Test the Fill Valve Shutoff
Sometimes the fill valve can’t shut off completely.
Watch the fill valve after the tank finishes refilling.
Signs of failure include:
a faint hissing sound
water trickling from the valve
the valve turning on and off repeatedly
Fix: Replace the fill valve. Modern replacement valves are inexpensive and universal.
3. Inspect the Flush Valve Seat
Even with a new flapper, the toilet may still leak if the flush valve seat is rough or damaged.
Lift the flapper and inspect the circular rim where it seals.
Look for:
mineral buildup
debris
rough or pitted porcelain
Fix: Clean the surface with a cloth or nylon pad to remove buildup. If the seat is damaged, you’ll probably need to replace the flush valve.
4. Check the Refill Tube Position
The small refill tube should direct water into the overflow tube but must not extend below the water level inside the tube.
If it does, it can create a siphon that slowly drains the tank.
Fix: Clip the refill tube to the top of the overflow pipe so the end sits above the opening.
5. Look for Hairline Tank Leaks
Rarely, a toilet tank may leak internally.
Signs include:
constant refill cycling
unexplained water loss from the tank
dampness around tank bolts or seals
If internal tank components are deteriorated, replacing the flush valve assembly or tank hardware may be necessary.
When Replacement Is the Better Option
If multiple components inside the tank are worn, replacing all the internal hardware can sometimes be easier than troubleshooting individual parts.
Complete toilet rebuild kits include:
fill valve
flapper
flush valve
tank bolts and seals
These kits are inexpensive and can restore older toilets to reliable operation.
When to Call a Plumber
Professional help may be needed if:
the toilet continues running after internal parts are replaced
the tank or bowl is cracked
drain or vent problems are suspected
Persistent running can waste hundreds of gallons of water per day, so it’s worth resolving quickly.
To Hire a Plumber…
If the repair turns out to be more complicated than expected, you can always find a plumber near you.
For hiring advice, see Trade Secrets for Hiring the Right Plumber.
Related Articles
If you’re not sure what’s causing the problem, see our
Toilet Repair and Troubleshooting Guide for a complete diagnostic overview.
Also see:
How to Fix a Running Toilet
How to Replace a Toilet Flapper
How to Replace a Toilet Fill Valve
How to Replace a Toilet Flush Valve
Toilet Repair Costs
