A toilet that leaks or runs are an easy homeowner fix—if you know how to diagnose the trouble. ID parts and problems with this handy guide, and hit the hardware store with confidence.

Know Your Parts to Fix a Leaking Toilet

Refill Tube

Replaces water in the bowl after flush. If the toilet runs intermittently, check that tube’s end is above the water level in the tank.

Ball Cock

On/off valve regulated by float ball fills tank and bowl after flush. If the toilet runs intermittently, the ball cock could be faulty and may need to be replaced.

Float Cup

When it comes time to retire an old ball-cock flush mechanism, the all-in-one plastic replacements stocked by home centers make for an easy fix. Float-cup mechanisms go in quickly and adjust easily for simple repairs.

Float Ball

Shuts off ball cock when water filling tank reaches the correct level.

Chain

Opens flapper at beginning of flush. If the toilet runs constantly, check that chain isn’t too short or long, thus interfering with flapper closing.

Overflow Tube

Prevents the tank from overflowing. If tank water is constantly draining into the tube, bend the arm of the float ball down slightly or lower the float cup on the replacement fill-valve assembly.

Flapper

Lifts to let tank water flow into the bowl. If the toilet runs intermittently, scrub mineral deposits off it (or flush-valve seat under it) to tighten the seal. If that doesn’t help, replace it.

Gasket

Seals connection between tank and bowl.

Wax Ring

Seals connection between the bottom of toilet and drain. If water leaks out the base of the bowl, replace the ring.

Closet Bolt

Holds bowl to the flange. If toilet rocks, tighten nuts attached to these bolts. To avoid cracking bowl, secure no more than a quarter-turn past finger-tight.

Closet Flange