Why Does My Toilet Keep Running? Causes and Fixes

A toilet that keeps running usually loses water through the flush valve or continues filling because the float, fill valve, chain, or water level is not working correctly. Watch one complete flush before buying parts. The direction of the water shows which component needs attention.

A running toilet can be obvious or nearly silent. This guide shows how to separate a leaking flapper, an incorrect water level, a fill-valve problem, and a leak at the base before you buy parts or arrange a repair.

Why Your Toilet Keeps Running

Lift the tank lid and flush while you watch. Everything you need to diagnose sits in plain view. The tank fills through the fill valve, the float shuts the valve off at the set water level, and the flapper seals the hole at the bottom between flushes.

The flapper fails first

The flapper is a rubber seal, and rubber degrades. After three to five years it warps, stiffens, or grows a coating of mineral scale, and it stops sealing the flush valve completely. Water then leaks from the tank into the bowl, the water level drops, and the fill valve runs to top it up. That cycle repeats around the clock.

The chain causes its own version of the problem. A chain with too much slack gets trapped under the flapper and holds it open. A chain set too tight prevents the flapper from seating at all. Either way, the tank never seals and the toilet never stops.

Fill valve and float problems

When the flapper checks out fine, look at the water level. Water spilling into the overflow tube means the float sits too high and the tank overfills. Adjust the float screw or clip until the water stops about 2.5 centimetres below the top of the overflow tube.

A fill valve that hisses, cycles on and off, or refuses to shut off has worn internals. Replacement valves cost $15 to $30 and install with basic tools. Old ballcock style valves in older Toronto and Markham homes fail more often than modern ones, and swapping to a current valve solves the problem for years.

What a Running Toilet Costs You in Toronto

Homeowners ignore running toilets because water looks free. The math says otherwise, especially at GTA water rates.

The water math

The EPA figure of 200 gallons per day equals roughly 757 litres, which works out to about 23 cubic metres per month. The City of Toronto charges just under $5 per cubic metre for water and wastewater in 2025. One running toilet therefore burns more than $100 every month it runs, and severe leaks waste several times that.

For scale, the average Toronto household uses about 230 cubic metres per year and pays about $1,078. A single neglected toilet doubles that annual consumption. The EPA also reports that household leaks overall waste more than 9,300 gallons per home per year, and toilets top the list of offenders.

Confirm the leak with the dye test

Silent leaks waste water without any running sound. Put a few drops of food colouring into the tank, wait fifteen minutes, and do not flush. Colour in the bowl proves water is passing the flapper. This test costs nothing and settles the diagnosis in one try, so run it on every toilet in the house once a year.

Your water meter gives you a second check. Pick a stretch when nobody uses water, note the meter reading, and read it again two hours later. Any movement means water left the house somewhere, and a leaking toilet stands first in line as the suspect. Landlords with basement suites and rental units should run this check between tenants, because a silent leak in an unoccupied unit runs for months unnoticed.

How to Fix a Running Toilet Yourself

Shut off the water at the valve behind the toilet, flush to empty the tank, and you have a safe workspace. No tools touch any pressurized line.

Replace the flapper in 30 minutes

New flappers are inexpensive, but matching the toilet matters more than choosing a package marked universal. Set the tank lid somewhere stable, photograph the existing chain position, and follow the replacement instructions for the toilet and part.

Buy a flapper matched to your toilet's make and model rather than trusting the universal label. Set the chain with slight slack, turn the water back on, and flush a few times to test. The tank refills and goes silent within about 30 seconds when the seal is right.

Adjust the float and replace the fill valve

Float adjustment takes two minutes. Turn the adjustment screw on the fill valve, or slide the clip on the float arm, until the fill stops below the overflow tube. Flush and confirm the valve shuts off cleanly.

A worn fill valve takes about an hour to replace. Shut off the supply, drain and sponge out the tank, disconnect the supply line, and swap the valve following the package instructions. If the supply connection, tank hardware, or shutoff is corroded, stop before forcing it. A small tank repair should not turn into a damaged valve or wet floor.

When to Call a Plumber Instead

Some running toilets outsmart the DIY fixes, and some hide bigger problems. Know the difference before you buy your third flapper.

Signs the problem is bigger than a flapper

Call a licensed plumber when you see any of these:

• The toilet still runs after a new flapper and fill valve
• The flush valve seat is cracked or pitted, so no flapper can seal against it
• Water pools around the base of the toilet
• The toilet runs and also rocks, gurgles, or drains slowly
• Your water bill stays high after every visible leak is fixed

A cracked flush-valve assembly may require the tank to come off. Water at the base points to the seal, flange, supply, or condensation and should be traced before the toilet is reset. These repairs fall within Seal Plumbing’s service and drain work across the GTA.

Repair or replace the toilet

A simple flapper or fill-valve repair may be practical when the porcelain, shutoff, supply connection, and flush components are otherwise sound. Replacement deserves consideration when parts are obsolete, the bowl or tank is damaged, the fixture remains unreliable after repair, or a renovation already requires the toilet to be removed.

Replacement makes particular sense when you already have other work planned. If you are adding a basement bathroom or renovating an ensuite, upgrading the old toilets in the same visit saves you a second service call.

Frequently Asked Questions

Why does my toilet keep running after I flush?

A worn flapper is the most common cause. The rubber seal loses its shape over time, lets water leak from the tank into the bowl, and forces the fill valve to keep refilling. A chain with too much slack or a float set too high produces the same constant running sound.

How do I know if my toilet flapper is bad?

Put a few drops of food colouring in the tank and wait fifteen minutes without flushing. If colour appears in the bowl, the flapper leaks. A bad flapper also shows visible warping, cracks, or mineral buildup when you lift the tank lid.

How much water does a running toilet waste?

The US Environmental Protection Agency reports that a constantly running toilet wastes 200 gallons of water or more every day. That equals roughly 757 litres a day, or about 23 cubic metres each month.

How much does it cost to fix a running toilet?

A replacement flapper costs $5 to $20 at any hardware store and takes about 30 minutes to install yourself. A plumber charges around $50 to $100 or more for a simple flapper repair, and the fix pays for itself quickly against the wasted water.

Can a running toilet increase my water bill?

Yes, by a lot. Toronto charges just under $5 per cubic metre for water in 2025, so a toilet wasting 200 gallons a day adds more than $100 a month to your bill. Many homeowners discover the problem only when the bill arrives.

How long should a toilet flapper last?

A toilet flapper lasts about three to five years with regular use. Hard water, in tank cleaning tablets, and frequent flushing shorten that lifespan. Check the flapper once a year with the food colouring test.

Repair the part that is actually leaking

If the tank adjustments do not stop the water, send the toilet model, a photo inside the tank, and where the water is moving or appearing. Seal Plumbing can then discuss repair versus replacement without pretending every running toilet has the same cause. Check the service area or request service online.