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Toilet keeps running? The three parts that usually cause it

General home information from Prufloop. Updated October 28, 2026.

The short answer. A running toilet is almost always the flapper, the chain or the fill valve. If water keeps flowing into the overflow tube, lower the float. If the tank refills on its own every so often, the flapper is leaking. If the chain is tangled or too short, the flapper can't seal. These parts are inexpensive; a plumber can replace them if you'd rather not.

What you can safely check

Take the tank lid off and watch. Water spilling into the overflow tube means the fill level is set too high: lower the float.
Put a few drops of food coloring in the tank and wait 15 minutes without flushing. Color in the bowl means the flapper is leaking.
Make sure the chain has a little slack and isn't caught under the flapper.
Turn off the valve behind the toilet before replacing parts.

When to call a plumber

The shut-off valve behind the toilet won't turn or leaks
Water leaks at the base of the toilet
New parts don't stop the running
The tank or bowl is cracked

What a plumber will usually do

Replaces the flapper, fill valve or flush valve
Replaces the shut-off valve and supply line
Resets the toilet on a new wax ring if it leaks at the base

Asking an AI assistant to book it

Once Prufloop launches (planned for Q4 2026 around Charlotte), you'll be able to ask the AI assistant you use something like this, and it can book a verified pro at a posted price in a real open slot. This is how it's planned to work; no assistant is connected yet.

Example request. “My toilet keeps running and the valve behind it is stuck. Book a plumber in Huntersville at their posted price.”

Before a job is booked, you see the pro's posted price, including any trip or diagnostic fee. Anything extra needs your OK first. When the work is done, you confirm it's fixed with a quick text. That's Proof of Done™.

Questions

Does a running toilet waste much water?

Yes. A steadily running toilet can waste hundreds of gallons a day, which shows up on your water bill.

Why does my toilet refill by itself at night?

That's a slow leak from the tank into the bowl, usually a worn flapper.

Can my AI assistant book a plumber for this through Prufloop?

Not yet. Prufloop is being built so the AI assistant you already use can book a verified plumber at a posted price, starting with the Charlotte-area pilot planned for Q4 2026 in Mecklenburg, Union, Cabarrus, Iredell, Gaston and Lincoln counties in North Carolina, plus York and Lancaster counties in South Carolina. No AI assistant is connected yet.

Are you a Charlotte-area plumber?

Free to join. Only pay on jobs completed: 10% on jobs under $2,500, less on bigger jobs, charged when the job is marked done. No lead fees. Founding pros get a guaranteed spot and founding terms locked for 24 months.

Secure your spot

How it works for pros