It's 2 AM and you hear it. That hiss from the bathroom. Before you call anybody, give it ten minutes. It might be a cheap piece of rubber, not a plumber's visit.
Last updated: October 2026 · By Gen X Still Standing
A toilet that keeps running often has a worn flapper. That's the rubber seal at the bottom of the tank. When it wears out, water sneaks past it into the bowl, and the tank keeps refilling.
A new flapper typically runs $10 to $25. A lot of service calls cost $100 to $150 just for the guy to show up.
Keep one hand near the shutoff valve the first time you turn the water back on. If it still leaks after a correct flapper swap, it's probably the fill valve or the valve seat, not the flapper.
Call a plumber if the shutoff valve won't close, the tank bolts leak, or you see a crack in the porcelain. Those aren't flapper problems.
I learned the trades hands-on and ran my own construction company in Colorado. I've watched other contractors do to homeowners exactly what this page teaches you to stop. Not knowing is where the upsell lives. Now you know.
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Why does my toilet keep running?
Often it's a worn flapper letting water sneak from the tank into the bowl. A chain with no slack can also be the problem. If it still leaks after a correct flapper swap, it's probably the fill valve or valve seat.
How much does a toilet flapper cost?
A new flapper typically costs $10 to $25 at a hardware store.
How do I know if it's the flapper?
Put a few drops of food coloring in the tank, wait 10 minutes without flushing, and look in the bowl. If color shows up, the flapper is leaking.
Do I need a permit to replace a flapper?
No. Replacing a flapper is permit-free maintenance.
What if it still runs after I swap the flapper?
If it still leaks after a correct swap, it's probably the fill valve or the valve seat. If the shutoff won't close, the tank bolts leak, or the porcelain is cracked, call a plumber.
Educational only. Follow the manufacturer's instructions and your local codes. When in doubt, call a licensed plumber. Built by a Gen Xer with AI, for Gen Xers.
