Why does my toilet keep running?

A toilet that runs constantly — or refills on its own every few minutes — is almost always a worn flapper or a faulty fill valve inside the tank. It's a small part failing, but a big water bill: a running toilet can waste 200+ gallons a day. The parts cost $10–$25, and this is the most DIY-friendly plumbing fix there is.

Likely causes

• Worn flapper — The rubber seal at the tank bottom warps with age and chlorine — water seeps into the bowl silently.
• Faulty fill valve — The toilet runs on after flushing or the valve hisses — the shutoff mechanism is worn.
• Chain or handle problem — A chain that's too long or kinked holds the flapper open.
• Cracked overflow tube — Water spills into the overflow — less common, needs a new flush valve assembly.

What you can check yourself

• Drop food coloring in the tank: if color appears in the bowl without flushing, the flapper leaks. Replace it — a 15-minute job, mostly no tools.
• Check the water level: it should sit about an inch below the overflow tube; adjust the fill valve if water spills over.
• Jiggle test first: if jiggling the handle stops the running, it's the chain or flapper alignment.

Typical cost

DIY parts run $10–$25. A plumber in Chicago, IL typically charges $150–$350 for the repair visit; full toilet replacement runs $350–$700 installed.

When to call a pro

Water on the floor at the base, a toilet that rocks, or a sewer smell — that's a wax-ring or flange problem, not a flapper. Call before the subfloor rots.

Plumber pros in Chicago, IL

• Environmental Systems Design · 175 W Jackson Blvd, Chicago, IL · +13123721200
• Mr. Rooter Plumbing of Chicago · 28 E Jackson Blvd, Chicago, IL · (847) 807-3978
• Millennium Piping Inc · 162 N Franklin St Ste 300, Chicago, IL · 13123450560
• Sewer Drain Cleaning Chicago · 27 N Wacker Dr Ste 133, Chicago, IL · (773) 678-5312
• Magic Men Service Inc · 306 S Halsted St, Chicago, IL · 3125979678
• US Chicago Plumbing For Paid version Home Service Chicago · 150 N Michigan Ave, Chicago, IL · (312) 465-1767
• Homex · 333 N Michigan Ave, Chicago, IL · +18554663948
• Jireh Plumbing · 1 E Erie St Ste 525, Chicago, IL · +17732998262

Get free quotes from Chicago, IL pros →

Data by Servik — verified local pros from official license records and public sources. Cost figures are typical ranges, not quotes; a pro's written estimate is the real number.