How to Fix a Running Toilet

Diagnose and repair the most common causes of a toilet that keeps running, including the flapper, fill valve, float and refill tube.

Difficulty: BeginnerTime: 20–45 minutesTypical cost: $8–$45

Safety first: Turn the toilet’s shutoff valve clockwise before removing tank components. If the valve is seized or begins leaking, stop and arrange professional service.

In this guide

Symptoms
Likely causes
Tools and materials
Step-by-step procedure
Common mistakes
When to call a professional

Common symptoms

Water continues flowing after the tank has refilled
The toilet cycles on briefly every few minutes
The handle must be jiggled to stop the water
Water is flowing into the overflow tube

Likely causes

Start with the simplest observable cause and avoid replacing parts until the failure has been identified.

A worn, warped or mineral-coated flapper
A chain that is too tight, too loose or snagged
A float set too high
A fill valve that no longer shuts off reliably
A refill tube pushed too far into the overflow pipe

Tools and materials

Adjustable pliers
Sponge or small towel
Replacement flapper or fill valve as required

Step-by-step procedure

Remove the tank lid and observe a complete flush. Identify whether water is leaking past the flapper or entering the overflow tube.
Check the flapper chain. Leave a small amount of slack when the flapper is closed so the chain cannot hold the flapper open.
Clean the flapper seat and inspect the rubber. Replace the flapper if it is stiff, cracked, misshapen or heavily coated with mineral deposits.
If water enters the overflow tube, lower the float according to the fill-valve design. Refill the tank and confirm the water stops below the marked fill line.
Replace the fill valve when adjustment does not stop the flow. Follow the valve manufacturer’s instructions and use the supplied rubber washer inside the tank.
Clip the refill tube above the overflow opening rather than pushing it down into the tube, which can create a siphon.
Restore the water, flush several times and inspect the tank connection and supply line for leaks.

Field tip: Add a few drops of food colouring to the tank and wait 15 minutes without flushing. Colour in the bowl confirms a leaking flapper.

Common mistakes to avoid

Replacing parts before observing where the water is escaping
Overtightening plastic nuts beneath the tank
Using in-tank chemical tablets that can deteriorate rubber seals

Verify the repair

Test the repaired component through several normal operating cycles. Watch, listen and feel for leaks, heat, movement, unusual noise or odour. Stop immediately if the condition worsens. Document the work and retain part numbers, receipts and manufacturer instructions for future maintenance.

When to call a professional

Call a plumber if the shutoff valve leaks, the tank is cracked, the toilet rocks at the floor, or water appears around the base.

Editorial note

This guide is written for general homeowner education. Building codes, product instructions, warranties, condominium rules and licensing requirements vary. The safest compliant method for your property always takes precedence.