Why Does My Toilet Keep Running? 6 Common Causes Explained
Why Does My Toilet Keep Running? 6 Common Causes Explained
A toilet that keeps running after flushing might seem like a minor inconvenience, but it can waste a surprising amount of water and increase your household water bill.
Sometimes the problem is obvious. You might hear water constantly refilling the cistern or notice a steady trickle running into the toilet bowl. Other times, the leak is almost silent and can go unnoticed for weeks.
According to the Queensland Government, a visibly leaking toilet can waste up to 18 buckets of water every day.
The good news is that many running toilet problems have relatively straightforward causes, such as a worn seal, faulty inlet valve or incorrectly adjusted float.
In this guide, we'll explain six common reasons your toilet keeps running, how to identify a possible leak and when it's time to contact a licensed plumber.
Why Does My Toilet Keep Running After Flushing?
When you flush a toilet, water stored in the cistern is released into the bowl. The cistern then refills through an inlet valve until the water reaches its intended level.
Once the cistern is full, the inlet valve should shut off and the toilet should stop running.
If water continues flowing, something may be preventing the cistern from sealing properly or stopping the refill process.
The problem generally involves one of two situations:
Water continuously entering the toilet bowl: Often caused by a worn flush valve seal, a flush mechanism that isn't closing properly or water overflowing inside the cistern.
The cistern constantly refilling: Often caused by a faulty inlet valve, incorrectly adjusted float or water escaping from the cistern into the bowl.
Understanding which problem you're experiencing can help narrow down the cause.
6 Common Causes of a Toilet That Keeps Running
1. A Worn or Damaged Flush Valve Seal
One of the most common causes of a running toilet is a worn seal at the bottom of the flush mechanism.
This seal helps prevent water from escaping from the cistern into the toilet bowl between flushes.
Over time, rubber seals can deteriorate, become distorted or develop a buildup of debris that prevents them from closing properly.
When this happens, water slowly escapes into the bowl, causing the cistern to refill repeatedly.
Common signs include:
Water trickling into the toilet bowl between flushes
The cistern refilling unexpectedly
A faint running-water sound
Water movement inside the bowl when the toilet hasn't been used
A plumber can inspect the flush valve and determine whether the seal or another component needs replacing.
2. A Faulty Toilet Inlet Valve
The inlet valve controls how water enters the toilet cistern after flushing.
Once the water reaches the correct level, the valve should close automatically.
If the inlet valve becomes worn, damaged or obstructed by debris, it may fail to shut off completely.
This can cause water to continue entering the cistern even after it has filled.
Common signs include:
A constant hissing or filling sound
Water continuing to enter the cistern after flushing
Water flowing into the internal overflow
The toilet taking an unusually long time to stop refilling
A faulty inlet valve may require cleaning, adjustment or replacement, depending on its condition.
3. An Incorrectly Adjusted or Faulty Float
Most toilet cisterns contain a float mechanism that helps regulate the water level.
As the cistern fills, the float rises and signals the inlet valve to stop supplying water.
If the float is incorrectly adjusted, obstructed or damaged, the inlet valve may not close at the appropriate water level.
This can cause the cistern to overfill, with excess water flowing into the toilet bowl through the internal overflow.
What should you look for?
If the water level inside the cistern continues rising until it reaches the overflow opening, the float or inlet valve may not be operating correctly.
The exact arrangement varies between toilet models, including modern dual-flush systems.
4. A Sticking Flush Button or Flush Mechanism
Sometimes the issue isn't with the water supply at all.
The flush mechanism itself may be sticking or failing to return to its normal position after the toilet is flushed.
This can prevent the flush valve from closing completely, allowing water to continue flowing into the bowl.
Common signs include:
The toilet continues flushing after the button is released
The flush button feels stuck or doesn't return normally
Water keeps entering the bowl immediately after flushing
The problem occurs intermittently rather than after every flush
The cause may be a sticking button, an incorrectly positioned component or wear within the flush mechanism.
If the issue continues, the mechanism should be inspected to identify the faulty component.
5. Sediment or Debris Inside the Cistern
Sediment, mineral deposits and other debris can sometimes interfere with the moving parts inside a toilet cistern.
For example, debris around a flush valve seal may prevent it from closing tightly.
Similarly, buildup within the inlet valve may affect how it opens and closes.
Possible symptoms include:
Intermittent leaking into the bowl
The toilet continuing to run after some flushes
A valve that doesn't shut off consistently
Visible sediment or buildup inside the cistern
Cleaning accessible components may help in some cases, but persistent problems can indicate that parts are worn or need professional attention.
6. Ageing or Damaged Cistern Components
Like other plumbing fixtures, toilet cistern components wear out over time.
Rubber seals can harden, plastic mechanisms can become brittle and moving parts may eventually stop operating as intended.
In older toilets, several components may be approaching the end of their useful life at the same time.
Common signs include:
Repeated running-water problems
Several previous cistern repairs
Intermittent flushing issues
Visible wear or deterioration inside the cistern
Depending on the toilet's condition, replacing individual components may be sufficient.
However, if the toilet is older and experiencing repeated problems, a licensed plumber can advise whether more extensive repairs or replacement would be worthwhile.
How to Tell If Your Toilet Is Leaking
Not every leaking toilet makes an obvious sound.
Some cistern leaks are slow enough that homeowners don't notice them until their water consumption increases.
Fortunately, there's a simple way to check whether water is escaping from the cistern into the bowl.
The Food Colouring Test
The Queensland Government recommends using food colouring to identify a possible leaking toilet cistern.
Here's how the test works:
Carefully remove the cistern lid, if it is designed to be removed easily.
Add a small amount of food colouring to the water inside the cistern.
Leave the toilet without flushing and watch for colour appearing in the bowl.
If the colouring enters the bowl without flushing, water is likely leaking past the flush mechanism.
Flush the toilet twice after the test to help prevent staining.
This test can identify water escaping from the cistern into the bowl, although it won't necessarily identify which component has failed.
If you discover a leak, the next step is to determine whether the flush valve, seal or another component requires attention.
Why Does My Toilet Keep Running Every Few Minutes?
If your toilet is quiet for several minutes and then suddenly starts refilling, it may be experiencing an intermittent refill cycle.
This can happen when water slowly escapes from the cistern into the bowl.
As the water level drops, the inlet valve opens to replace the lost water.
Once the cistern reaches its normal level, the valve closes again.
The cycle can repeat throughout the day, even when nobody is using the toilet.
A worn flush valve seal is one possible cause, but the inlet valve and other cistern components should also be checked.
How Much Water Can a Running Toilet Waste?
A constantly running toilet can waste significantly more water than many homeowners realise.
The Queensland Government states that a visibly leaking toilet can waste up to 18 buckets of water per day.
Even a smaller, less noticeable leak can contribute to unnecessary water consumption over time.
The amount wasted depends on the severity of the leak and how continuously water is escaping.
If your water bill has increased unexpectedly, checking your toilets is a sensible place to start.
You can also use your property's water meter to investigate unexplained water consumption.
For more information, read our guide on How to Tell If You Have a Hidden Water Leak in Your Home.
Can You Fix a Running Toilet Yourself?
Some running toilet problems are relatively simple to identify.
Homeowners can safely start by observing how the toilet behaves, checking for visible water movement and performing the food colouring test.
In Queensland, certain limited plumbing maintenance tasks are classified as unregulated work.
According to the Queensland Building and Construction Commission (QBCC), examples include replacing specific toilet cistern components such as a drop valve washer, float valve washer or suction cup rubber.
However, this does not mean every toilet repair can legally be completed without a plumbing licence.
Replacing a toilet, undertaking broader plumbing repairs or working on regulated plumbing components generally requires an appropriately licensed tradesperson.
If you're unsure what is causing the problem or whether a particular repair is permitted, contacting a licensed plumber is the safest approach.
Should You Repair or Replace a Running Toilet?
In many cases, a running toilet can be repaired without replacing the entire fixture.
Problems involving worn seals, faulty inlet valves or sticking flush mechanisms can often be resolved by repairing or replacing the affected components.
However, replacement may be worth considering when:
The toilet has recurring problems despite previous repairs
Multiple cistern components are deteriorating
Replacement parts are difficult to obtain
The cistern or toilet pan is cracked or damaged
The existing toilet is outdated and no longer operating reliably
A licensed plumber can assess the condition of the toilet and explain whether a repair or replacement is the more practical option.
When Should You Call a Plumber for a Running Toilet?
A toilet that continues running shouldn't be ignored, particularly if the problem persists after basic checks.
Consider contacting a licensed plumber when:
Water continuously flows into the toilet bowl
The cistern keeps refilling without being flushed
The flush button or mechanism repeatedly sticks
You suspect a faulty inlet valve
Your water bill has increased unexpectedly
Previous repairs haven't resolved the problem
The toilet is leaking externally or showing signs of damage
A running toilet is not always a plumbing emergency, but addressing it promptly can help prevent unnecessary water waste and ongoing inconvenience.
If water is leaking onto the floor or causing damage, arrange professional assistance as soon as possible.
Who Is Responsible for Fixing a Leaking Toilet in Brisbane?
For owner-occupied properties, the homeowner is generally responsible for maintaining the plumbing fixtures within their property.
The Queensland Government explains that property owners are responsible for plumbing and fittings on their side of the water meter connection point, including water lost through leaks.
In Brisbane, Urban Utilities manages the public water and wastewater network, while private plumbing repairs generally remain the property owner's responsibility.
If you're renting, report the problem to your property manager or landlord so the appropriate repair arrangements can be made.
Running Toilet in Brisbane? MSV Plumbing Services Can Help
A toilet that keeps running can be frustrating, but identifying the cause early can help reduce water waste and prevent the problem from continuing.
Whether the issue involves a worn flush valve seal, faulty inlet valve or damaged cistern component, the right repair depends on what's causing the water to escape.
At MSV Plumbing Services, we provide residential plumbing services across Brisbane, helping homeowners with leaking toilets, faulty fixtures, damaged pipework and other common plumbing problems.
Founded by Matthew Main, a licensed plumber with more than 15 years of industry experience, MSV Plumbing Services focuses on practical solutions and reliable workmanship.
Is your toilet constantly running or leaking? Contact MSV Plumbing Services to arrange a plumbing inspection or repair.
About the Author
Matthew Main – Founder, MSV Plumbing Services
Matthew Main is the founder of MSV Plumbing Services and a licensed Queensland plumber with more than 15 years of hands-on experience. He established MSV Plumbing Services in 2020 and provides residential and commercial plumbing services across Brisbane, including plumbing repairs, blocked drains, hot water systems and emergency plumbing.
Learn more about Matthew's experience and qualifications.
Sources & Further Reading
The following official Queensland resources provide additional information about leaking toilets, household water consumption and licensed plumbing work.
1. Queensland Government – Household Water Leaks
Official guidance on detecting leaking toilets, checking your water meter, performing the food colouring test and understanding household water loss.
https://www.qld.gov.au/environment/water/residence/use/home/leaks
2. Queensland Building and Construction Commission – Plumbing Problems: What Queensland Homeowners Need to Know
Information about regulated plumbing work, toilet repairs and the importance of using appropriately licensed plumbers in Queensland.
https://qbcc.qld.gov.au/news/plumbing-problems-heres-what-queensland-home-owners-need-know
3. Queensland Building and Construction Commission – Unregulated Plumbing Guide
Explains which limited plumbing maintenance tasks homeowners may undertake without a plumbing licence, including certain toilet cistern washer replacements.
https://www.qbcc.qld.gov.au/news/unregulated-plumbing-guide
4. Brisbane City Council – Water Supply and Sewerage
Information about Brisbane's water supplier, Urban Utilities, and responsibilities for water leaks, wastewater services and private plumbing.
5. Logan City Council – Water Leaks and Water Main Breaks
Local government guidance on checking for toilet cistern leaks, including using food colouring to identify water escaping into the bowl.
https://www.logan.qld.gov.au/residents/water-and-wastewater/water-leaks-and-mater-main-breaks
Disclaimer
This article provides general information about running toilets, leaking cisterns and residential plumbing in Queensland. Plumbing systems and toilet mechanisms vary between properties, and the symptoms described may have several possible causes. While certain minor plumbing maintenance tasks are permitted without a licence in Queensland, regulated plumbing work must be completed by an appropriately licensed tradesperson. For advice specific to your property, contact a licensed plumber.
