Why Does My Toilet Keep Running? (And How to Fix It)

That constant hiss or periodic refilling isn't just annoying — a running toilet can waste 200+ gallons of water a day and quietly inflate your water bill. Here's why it happens.

The usual culprits

• A worn flapper. The rubber flapper at the bottom of the tank hardens over time and stops sealing, letting water trickle into the bowl. This is the #1 cause and an easy fix.
• A bad fill valve. If the valve won't shut off, the tank overfills and drains into the overflow tube.
• The float is set too high. Water rises above the overflow tube and runs continuously.
• A too-short or tangled flush chain that holds the flapper slightly open.

Quick things to check yourself

Lift the tank lid. If the water is spilling into the center overflow tube, lower the float. If the water level is fine but you still hear running, the flapper is likely the problem — push it down with a stick; if the running stops, replace the flapper.

When to call a plumber

If you've swapped the flapper and adjusted the float and it still runs, the fill valve or the toilet's internals may need replacing. That's a quick, affordable toilet repair for us — usually under an hour and well worth it given how much water a running toilet wastes.