If your toilet has constant running water, the fix is usually much simpler than people think. Most plumbers will tell you it’s almost always one of two parts inside the tank — and you can fix it in minutes.
The #1 Cause: A Worn Flapper
Inside the tank, the flapper valve seals the opening that lets water flow into the bowl.
When it becomes warped, cracked, or stiff, water slowly leaks through — and the tank keeps refilling nonstop.
✔ Simple Plumber’s Fix (10–15 minutes)
- Turn off the water supply (valve behind the toilet).
- Flush to empty the tank.
- Unhook the old flapper from the overflow tube.
- Take it to a hardware store and buy the same size replacement.
- Snap the new flapper in place.
- Turn water back on and test.
💰 Cost: Usually under $10.
🔧 Difficulty: Very easy.
The Second Common Cause: Fill Valve Set Too High
If water constantly trickles into the overflow tube:
- Adjust the float lower using the adjustment screw or clip.
- Water level should sit about 1 inch below the overflow tube.
If adjusting doesn’t help, replacing the fill valve is inexpensive and straightforward.
Quick Test to Confirm a Flapper Leak
Put a few drops of food coloring in the tank.
Wait 15–20 minutes without flushing.
If color appears in the bowl → the flapper is leaking.
Why Fix It Quickly?
A running toilet can waste hundreds of gallons per day, increasing your water bill significantly.
Bottom Line
In most cases, the “experienced plumber’s secret” is simply:
👉 Replace the flapper.
👉 Adjust or replace the fill valve.
No expensive tools. No major repairs.
If you’d like, I can also show you how to tell which internal toilet system you have before buying parts, so you don’t get the wrong replacement.
