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Most repairs are modest. A flapper, a fill valve or a new wax ring fixes the majority of running and leaking toilets, and none of these parts is hard to find. What makes a toilet problem costly is time: a slow leak at the base can soak the subfloor and the ceiling below for months before anyone sees a stain.
When a toilet is old, cracked or constantly clogging, replacement becomes the better repair. Current low-flow toilets use much less water per flush than older models, and a well-chosen one clears waste just as well.
Signs your toilet needs repair, from a running tank to a soft floor
- You hear water trickling into the bowl, or the tank refills on its own between flushes.
- The handle has to be held down or jiggled to finish a flush or to stop the water.
- The flush is weak or needs a second try, or the bowl drains slowly and gurgles.
- Water appears on the floor around the base after flushing.
- The toilet rocks or shifts when someone sits on it.
- The flooring around the toilet is stained, lifting or soft, or a stain shows on the ceiling below.
Running toilet repair: flapper, fill valve and the dye test for silent leaks
A toilet that runs is almost always losing water in one of two ways. Either the flapper at the bottom of the tank no longer seals, so water seeps into the bowl and the fill valve keeps topping up the tank, or the fill valve doesn't shut off and water spills into the overflow tube. Lift the lid and look: if the water rises above the top of the overflow tube and pours into it, the fill valve or its float needs adjusting or replacing; if the level is right but the tank still refills now and then, the flapper is the likely culprit. A chain that is too short or tangled can also hold the flapper open.
Some leaks make no sound at all. The City of Toronto's leak check is easy: add food colouring or a dye tablet to the water in the tank, leave the toilet unflushed for 10 to 15 minutes, then look at the bowl. Any colour there means the tank is leaking into the bowl. The dye test is worth doing even when you hear nothing, since the City also warns that a leaking toilet can waste up to 20 cubic metres of water a day.
Weak flush or clogged toilet: telling the causes apart
A weak flush and a partial clog look alike, since the bowl empties slowly in both cases. Check the tank first: if the water sits well below the fill line marked on the tank or the fill valve, the flush has too little water to work with, and adjusting the float usually fixes it. If the level is right, look under the rim: mineral scale can block the small rim holes and the siphon jet at the bottom of the bowl, especially where water is hard, and a plumber can clean them out.
If the water rises high in the bowl and drains slowly after every flush, something is lodged in the trapway, the curved passage moulded into the bowl. A flange plunger, the kind with a sleeve that fits into the drain opening, clears most clogs; a closet auger reaches further without scratching the porcelain. When plunging doesn't help, when several fixtures drain slowly, or when water comes up in the tub or a floor drain as the toilet is flushed, the blockage is in the drain line or the vent, and that is a job for a plumber.
Leak at the base or a rocking toilet: wax ring replacement and subfloor damage
Water around the base that shows up after each flush usually means the wax ring, the seal between the toilet's outlet and the floor flange, has failed. A toilet that rocks is often the cause, since every wobble breaks the seal a little more. Tightening the bolts can't restore a crushed ring, and overtightening can crack the porcelain. The repair is to shut off and empty the toilet, lift it, scrape away the old wax, check the flange, then reset the toilet on a new ring, shimmed level so it stays put.
Before blaming the seal, rule out the other sources: a sweating tank, a leaking supply connection, the bolts between tank and bowl, or a crack in the porcelain. If the flange is cracked, corroded or sits below the finished floor, it needs repair or a spacer so the new ring can seal.
A leak that has run for a long time rarely stops at the surface. Water seeping under the flooring rots the subfloor and can stain or soften the ceiling below. If the floor around the toilet feels soft or spongy, the plumber will see the extent of it once the toilet is lifted, and a water damage restoration company can dry and repair the structure before new flooring goes down.
What not to flush to keep your toilet and drains clear
Many clogs start with things that were never meant for a toilet. The City of Toronto lists the items below among those to keep out of toilets and drains. A small covered wastebasket in every bathroom gives everyone an easy alternative.
- Wipes of any kind, including bathroom, baby and cleaning wipes.
- Tampons, sanitary pads and liners, and condoms.
- Cotton swabs, dental floss, facial tissue and paper towel.
- Fats, oils and cooking grease.
- Medication, whether pills or liquid.
- Household hazardous products such as paint, pesticides and cleaning products.
Toilet repair or a new low-flow toilet?
Tank parts are standard and easy to replace, so a running toilet on its own is rarely a reason to buy a new one. Replacement makes more sense when the porcelain is cracked, when the toilet clogs often despite careful use, when parts for an older or unusual model can't be found, or when it is an old high-volume model that uses much more water per flush than current ones.
When choosing a new toilet, measure the rough-in, the distance from the finished wall to the centre of the drain, and think about bowl height and shape for the people who will use it. Taking out the old toilet is also the right moment to replace the shut-off valve and supply line and to inspect the flange and subfloor.
Low-flow toilet rebates: check your municipality before you buy
Some municipalities encourage water savings with a rebate on a new low-flow toilet. These programs come and go, are often limited to residents with a municipal water account, and may ask for proof of purchase and a photo of the new toilet showing its flush rating. The City of Lethbridge, for example, runs its 2026 program from April 22 through December 31, or until funding runs out.
Before replacing a toilet, look on your city's or utility's website for a current program, read the eligibility rules and keep the receipt and the label.
When to call a licensed plumber for toilet repair
Replacing a flapper or adjusting a float is routine upkeep. Call a plumber when the toilet keeps clogging, when water backs up elsewhere in the house, when the flange or the drain beneath it is damaged, when the shut-off valve won't close, or when a toilet has to be moved or added.
In Quebec, plumbing work is reserved for holders of the right licence from the Régie du bâtiment du Québec, and the CMMTQ describes the narrow exception for owners working on the single-family home they live in. In other provinces, ask the provincial licensing body or your municipality who may do the work and whether moving a toilet needs a permit.
Toilet Repair: frequently asked questions
Why does my toilet refill by itself every so often?
That's usually a slow leak from the tank into the bowl, most often a worn or warped flapper or a dirty seat under it. As the level in the tank drops, the fill valve switches on to top it up. A dye test confirms it, and a new flapper that matches the flush valve usually solves it.
Is it safe to keep using a toilet that leaks at the base?
Try not to. Each flush pushes some waste water under the toilet and into the floor, which is unsanitary and damages the subfloor. Use another bathroom if you can, and have the wax ring replaced soon.
Should I pour chemical drain cleaner into a clogged toilet?
It's better not to. Chemical cleaners rarely clear a toilet clog, they can harm some pipes and seals, and they leave caustic water in the bowl for whoever plunges it next. Use a flange plunger or a closet auger, and call a plumber if those don't work.
How do I stop a toilet that is about to overflow?
Close the shut-off valve behind the toilet by turning it clockwise. If you can't reach it or it won't turn, lift the tank lid, press the flapper down and raise the float to stop the filling. Don't flush again until the clog is cleared.
Sources
Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides
