Repair a water heater under 8 years old when the fault is a component — thermocouple, element, gas valve, thermostat — because those are $150–$800 fixes. Replace it once it is past 10, or the moment water is coming from the body of the tank, because a perforated tank cannot be patched. A tank swap runs $1,200–$2,500 installed. The one thing worth doing before either decision is finding out where the water is actually coming from.
The decision rule in one paragraph
Under 8 years, single fault, no rust in the hot water, no water from the tank itself — repair. Between 8 and 10, repair only if the quote is modest and the tank has been flushed regularly. Past 10, put the money toward a replacement rather than a part, because you would be buying a component for a vessel already at the end of its Ontario service life. Any leak from the tank seam or the base ends the discussion at any age.
What common water heater repairs cost in the GTA
- Diagnostic service call: $90–$150, typically credited toward the work if you proceed
- Thermocouple, on a gas tank that lights and will not stay lit: $150–$300
- Gas control valve, where the pilot lights but the burner never fires: $400–$600
- Heating element on an electric tank — lukewarm water often means the lower one has gone: $200–$400
- Thermostat, T&P relief valve, drain valve or a leaking fitting: small parts at the bottom of the $150–$800 range
- Minor repairs generally: $150–$800, and worth considering if the unit is under 8 years old
Tankless repairs sit higher because the diagnosis is more involved and the parts are brand-specific: flow sensors, igniters and control boards on a wall-hung unit are not the same class of job as a thermocouple on a tank.
What a replacement costs
- Gas or electric tank, installed, including removal of the old unit: $1,200–$2,500
- Tankless conversion, installed with the venting and gas work: $3,500–$6,500
- Owning a tank outright over its life: $1,500–$3,000 for a quality gas unit plus occasional maintenance
- Renting instead: $25–$45 a month with annual increases, roughly $4,500–$8,000 across a 15-year tank life
That last pair of rows is the comparison most GTA households never run. A rented tank costs two to four times what the same appliance costs to own, and the rental agreement often outlives the tank. The full picture is in what it costs to replace a water heater in Ontario.
Find where the water is coming from before you decide anything
Water on the floor is not automatically a dead tank. Dry the area completely, put paper towel down at each of the points below, and check it a few hours later. Which one is wet decides whether you are looking at a small repair or a replacement.
- The discharge pipe from the T&P valve — repairable, and often a thermal expansion problem rather than a valve problem
- The drain valve at the base — repairable, and usually just a plastic valve that has stopped reseating after a flush
- The cold inlet or hot outlet fittings at the top — repairable; unions and nipples loosen and corrode
- Condensation running down a cold gas tank in a humid basement — not a leak at all, and common in July
- A relief line from a nearby appliance that happens to drain past the tank — not the water heater
- The seam or the base of the tank itself — not repairable; the steel has corroded through and it needs replacing now
Three faults people replace a tank over, and should not
Free quotes, written pricing.
The first is a pilot that keeps going out on a modern gas tank. Current tanks have a sealed combustion chamber with a flame-arrestor screen at the base, and in a basement with a nearby dryer or a workshop that screen loads up with lint and dust. A blocked screen starves the pilot. Cleaning it is a service call, not a new water heater.
The second is an electric tank producing no hot water at all. Behind the upper access panel there is a high-limit reset button — the ECO — that trips after an overheat event. Pressing it is free; finding out why it tripped is the actual repair, and it is usually a failed thermostat.
The third is hot water running out far sooner than it used to, with no leak and no noise. That is often a cracked dip tube letting cold water mix straight into the hot outlet, which is a cheap part. Those and the rest are set out in why a water heater stops producing hot water.
Repair or replace, compared
- Cash today — repair $150–$800; replacement $1,200–$2,500 for a tank
- What it buys — repair returns the unit to whatever life it had left; replacement restarts an 8-to-12-year clock
- Downtime — both are normally finished in one visit, and a tank swap takes a few hours
- Risk — a repaired 11-year-old tank can still perforate onto a finished floor; a new one comes with a warranty
- Efficiency — a repair changes nothing; a new tank is better insulated and loses less heat standing still
- Opportunity — a replacement is the natural moment to price a tankless conversion or to end a rental agreement
Check the warranty before you agree to either
Tank water heaters carry a manufacturer warranty on the tank itself, commonly six to twelve years depending on the model, and it usually runs to the original purchaser with proof of purchase. A tank that fails inside that window often means a free replacement vessel with the installation billed separately.
So before you accept a replacement quote, find the serial number on the rating label, note the model, and ask the contractor to check coverage. On a rented unit the answer is different again: repairs are the rental provider's responsibility, and paying someone else to fix their tank is money you do not need to spend.
The verdict
- Under 8 years, one component at fault, no rust and no tank leak — repair
- Eight to 10 years, quote under a few hundred dollars, flushed regularly — repair and start planning
- Past 10 years with any significant repair quote — replace
- Water from the tank seam or base at any age — replace immediately and shut the water off
- Rusty hot water, or repairs in two consecutive years — replace
- Renting the current unit — get the buyout terms before you price anything else
The best version of this decision is the one you make on a Tuesday rather than the morning of a cold shower. If your unit is heading past a decade, price the replacement while nothing is wrong — that is when a tankless conversion, a rental buyout and an off-peak install date are all still on the table. Keeping up with water heater maintenance is what buys you that timing, and how long a water heater lasts in Ontario tells you where yours sits.
ZK Mechanical repairs and replaces water heaters across the GTA and Hamilton, with a diagnostic that gets credited toward the work and written pricing on both options before anything starts. If you have water on the floor right now, shut the supply off and call us.
Frequently asked questions
When should I replace rather than repair my water heater?
Replace once the unit is past 10 years, once any repair quote is large relative to the $1,200–$2,500 a new tank costs installed, or the moment water appears from the tank body itself. Repair is the right call under 8 years for an isolated component — thermocouple, element, gas valve or thermostat. Between 8 and 10 it depends on the size of the quote and whether the tank has been flushed each year.
How much does it cost to repair a water heater in the GTA?
Most repairs fall between $150 and $800, plus a $90–$150 diagnostic that is usually credited toward the work. A thermocouple that will not hold the pilot is $150–$300. A gas control valve where the pilot lights but the burner never does is $400–$600. A heating element on an electric tank is $200–$400. Tankless repairs run higher because the parts are brand-specific and the diagnosis takes longer.
How much does a new water heater cost installed?
A gas or electric tank runs $1,200–$2,500 installed, which covers the unit, removal of the old one and the labour. A tankless conversion runs $3,500–$6,500 including the venting and gas work it needs. Ask for an itemized quote either way — permit, disposal and any gas or venting changes should appear as their own lines rather than being discovered on installation day.
Can a leaking water heater be repaired?
It depends entirely on where the water is coming from. Leaks at the T&P discharge, the drain valve, or the inlet and outlet fittings are all repairable by replacing the part. A leak from the seam or the base of the tank is not — the steel has corroded through from the inside and the vessel has to be replaced. If you see water on the floor, shut off the water supply and the gas or breaker, then call.
Is my water heater still under warranty?
Quite possibly. Tank warranties commonly run six to twelve years on the vessel itself, generally to the original purchaser with proof of purchase, and a covered failure means a replacement tank at no charge with the installation billed separately. Find the model and serial number on the rating label before you accept any quote. If the unit is rented, repairs are the provider's responsibility, not yours.