No hot water usually has a simple cause: a gas pilot that has gone out, a gas control left on vacation, a tripped breaker or high-limit switch on an electric tank, a power-vent unit that has lost power or has a blocked vent, or a tankless unit showing an error. Check the fuel and power first, read any error light, and stop if you smell gas or see scorching.
- Start with the basics: is the gas on, is the power on, is the control set correctly, is there an error code?
- On a standing-pilot gas tank, a pilot that will not stay lit is the most common cause; relighting per the label is an owner task.
- On an electric tank, a tripped breaker or high-limit switch points to a fault; do not keep resetting it.
- Power-vent tanks need electricity and a clear vent; in winter, snow or frost at the termination is a common cause.
- Gas smell, scorching, a CO alarm or water near electrical parts means stop and call.
01 /What should I check first when there is no hot water?
Check whether the problem is the whole house or one fixture, then check the water heater's energy supply and controls. Those two steps sort most no-hot-water calls in a few minutes.
- Whole house or one tap?
If one faucet or shower is cold but others are hot, the problem is that fixture's mixing cartridge or anti-scald valve, not the water heater.
- Is the tank itself hot?
Carefully feel the hot outlet pipe on top of the tank. A hot pipe with cold taps suggests a closed valve or fixture issue; a cold pipe means the heater is not heating.
- Energy supply
Gas: are other gas appliances working? Is the gas valve on the supply pipe to the heater open (handle parallel to the pipe)? Electric: is the breaker on? Power vent, heat pump and tankless: is the unit plugged in and powered?
- Control setting
Gas controls can be left on PILOT or VACATION after maintenance. Heat pump units can be in a vacation or off mode.
- Error lights and codes
Most power-vent, heat pump and tankless units flash a code or show one on a display. The meaning is in the manual or on a label inside the cover.
- Leaks
No hot water plus a leaking tank usually means the tank has failed. See hot water tank leaking.
The Water Heater Troubleshooter runs this same sequence and ranks causes by fuel type, including the Calgary winter cause: a power-vent or direct-vent termination blocked by snow or frost.
02 /Why is my gas water heater not heating?
A conventional gas tank that produces no hot water usually has a pilot that has gone out or will not stay lit. Other causes are a gas control left on pilot or vacation, a closed gas valve, a tripped flame-arrestor safety on newer tanks, or a failed gas control.
| Cause | How to recognise it | Owner check or pro job |
|---|---|---|
| Pilot out | No flame visible through the sight glass | Relight following the label; see pilot light won't stay lit if it goes out again |
| Control on PILOT or VACATION | Pilot lit, burner never fires | Turn the knob to your normal setting |
| Gas supply valve closed or gas off at the meter | No other gas appliances work either | Open the heater's valve; for a meter or utility issue, call the gas utility |
| Thermocouple failing | Pilot lights but goes out when you release the button | Replaceable part; many owners call a technician |
| Flame-arrestor or thermal lockout (newer tanks) | Pilot will not light or goes out repeatedly; lint or dust around the air intake | Pro job: clean and reset per the manufacturer |
| Gas control high-limit tripped or control failed | Pilot will not relight at all; water was too hot before it failed | Pro job: the control is usually replaced |
| Burner or control has been under water | After a flood or major leak | Do not use; technician inspection and control replacement |
A conventional gas tank with a standing pilot powered by a thermocouple usually keeps working in a power outage, because its control needs no household electricity. Power-vent tanks do not; Natural Resources Canada notes they require electricity and cannot produce hot water during an outage. See water heaters in a power outage for what to do while the power is off.
03 /Why is my power-vent water heater not working?
A power-vent water heater has a fan that pushes exhaust out through a side wall and electronic ignition instead of a standing pilot. When it produces no hot water, the cause is usually power, the vent, the fan or the ignition sequence, and the unit usually flashes a code that tells you which.
- Power: check the plug and outlet, the breaker, and any switch near the unit. A tripped GFCI outlet in a basement is a common culprit.
- Blocked vent or intake: snow drifts, frost build-up or ice at the wall termination stop the pressure switch from proving draft, so the burner never lights. This is the classic Calgary cold-snap failure. See power vent water heater in winter.
- Condensate: a blocked or frozen condensate line or trap can stop some units.
- Fan: a loud, grinding or silent fan points to a failing blower.
- Ignition: a failed igniter or dirty flame sensor causes repeated attempts, then a lockout code.
Clearing snow from the termination by hand and cycling the power is an owner task. Anything inside the unit is a job for a licensed gas technician. Power vent troubleshooting walks through the start-up sequence stage by stage.
04 /Why is my electric water heater not heating?
An electric tank that produces no hot water usually has a tripped breaker, a tripped high-limit (ECO) switch on the upper thermostat, or a failed upper element. The upper element heats first; if it fails, the lower element never gets its turn, so the whole tank goes cold.
| Cause | How to recognise it | Owner check or pro job |
|---|---|---|
| Breaker tripped | Breaker in the middle or off position | Reset once; if it trips again, leave it off and call |
| High-limit (ECO) tripped | Breaker on, no heat | With the breaker OFF, the red reset button behind the upper panel can be pressed; repeated trips mean a fault |
| Upper element failed | No hot water at all | Test with a meter with power off; replace element |
| Upper thermostat failed | Element fine but never energised | Test and replace thermostat |
| Elements dry-fired after draining | Tank was powered while empty | Replace elements; refill fully before power next time |
| Wiring fault | Scorch marks, melted insulation, burning smell | Stop; electrician or technician |
05 /Why is my heat pump or tankless water heater not making hot water?
Heat pump and tankless units are controlled electronically, so the first step is to read the display or error code. Most faults have a code, and the manual lists what each means.
| Unit | Common causes | Owner checks |
|---|---|---|
| Heat pump (hybrid) | Breaker tripped, dirty air filter, room too cold for the compressor, condensate drain blocked, compressor lockout, failed backup element | Check power, clean the filter, check the condensate line, switch to hybrid or electric mode if the room is cold, note the error code |
| Tankless (gas) | Gas off, power off, flow below the activation rate, scale on the heat exchanger, blocked vent or intake, freezing, ignition fault | Check gas and power, open the tap wider, clean the inlet filter, check the vent termination, note the error code |
| Tankless (electric) | Breaker(s) tripped, flow below activation, element failure | Check each breaker, open the tap wider, note the code |
A tankless unit that works at a shower but not at a low-flow bathroom tap is usually below its minimum activation flow. A heat pump unit that slows down in a cold basement in winter is using its elements more, which is normal; a unit that stops entirely has a fault. For how each technology works, see heat pump water heaters and tankless vs tank.
06 /When should I call a technician for no hot water?
Call a licensed gas technician for anything inside a gas control, burner, venting or ignition system, and an electrician or qualified technician for electrical faults. Relighting a pilot by following the label, resetting a breaker once, clearing snow from a vent and cleaning a filter are owner tasks; replacing gas controls, thermocouples inside sealed combustion chambers and wiring are not.
When you call, have the fuel type, the age from the rating plate, the error code, what you checked, and whether the pilot lights. That shortens the visit. If the tank is old, leaking or needs an expensive part, compare the repair with a replacement using the Tank Lifespan Predictor and the replacement cost guide, then request quotes.
FAQQuestions people ask
Why do I suddenly have no hot water?
The most common sudden causes are a gas pilot that has gone out, a tripped breaker or high-limit switch on an electric tank, a power-vent unit that has lost power or has a blocked vent, and a tankless unit in an error lockout. Check fuel, power, the control setting and any error code first.
Does a gas water heater work without power?
A conventional tank with a standing pilot and thermocouple-powered control usually does. Power-vent and many newer electronic-ignition models need electricity and will not heat during an outage.
Why does my electric water heater keep tripping the breaker?
Usually a shorted element, a wiring fault or a failing thermostat. Do not keep resetting it. Leave the breaker off and have the element and wiring tested.
Why is there no hot water in one bathroom only?
That points to the fixture, typically a worn mixing cartridge or a pressure-balancing or anti-scald valve set too low, not the water heater.
Where is the reset button on a water heater?
On electric tanks, the red high-limit reset is on the upper thermostat behind the upper access panel. Turn the breaker off before opening the panel. Most gas tank controls have no user reset; power-vent units reset by cycling the power.
How long does it take a water heater to heat up after relighting?
A gas tank usually recovers in roughly an hour or so and an electric tank takes longer, depending on size, input and the temperature of the incoming water. Heat pump units in heat pump mode are slower still.