Water Heating
Water Heater Troubleshooting: A Homeowner's Guide
March 24, 2026 · 9 min read
Key Takeaways
- No hot water? Check the pilot light (gas) or breaker (electric) before calling for repair
- Rumbling or popping sounds usually mean sediment buildup — a simple tank flush often fixes it
- A leaking water heater from the bottom typically means a failed tank — replacement is usually necessary
- Rusty or discoloured hot water often comes from a corroded anode rod, not necessarily a failing tank
In This Article
A water heater problem always seems to happen at the worst possible time — a cold morning shower, guests arriving, or laundry day. Before calling for emergency repair, many common water heater issues have straightforward causes that homeowners can diagnose themselves. This guide walks through the most frequent problems, their likely causes, and what you can safely check before scheduling a service call.
No Hot Water at All
Gas Water Heaters
- Pilot light out: The most common cause. Check the viewing window at the bottom of the tank — you should see a small blue flame. If it’s out, follow the relighting instructions on the unit’s label. If the pilot won’t stay lit, the thermocouple may need replacing ($20–$40 part, $100–$150 for service)
- Gas supply: Verify the gas valve on the supply line is fully open. Check if other gas appliances (stove, furnace) are working — if not, you may have a gas supply issue
- Thermostat setting: The temperature dial on the gas valve should be set to 49–60°C. If it was accidentally turned to “Vacation” or “Pilot,” no heating occurs
Electric Water Heaters
- Tripped breaker: Check your electrical panel. Electric water heaters use a dedicated 240V circuit. Reset the breaker if it’s tripped. If it trips again immediately, there’s an electrical fault that needs professional diagnosis
- High-limit reset button: Behind the upper access panel (turn off power first), there’s a red reset button. If it’s tripped, press it to reset. Frequent tripping indicates a failing thermostat or element
- Heating element failure: Electric heaters have two elements (upper and lower). If one fails, you’ll get lukewarm water; if both fail, no hot water at all. Element replacement costs $150–$300
Not Enough Hot Water
Running out of hot water quickly usually points to one of these issues:
- Sediment buildup: GTA’s hard water deposits calcium and minerals at the bottom of the tank, reducing the effective volume and insulating the water from the burner. A tank that holds 50 gallons might only have 30 gallons of usable space after years of sediment accumulation. Annual flushing prevents this
- Undersized tank: If your household has grown or your hot water usage patterns have changed, your existing tank may simply be too small. A family of four typically needs a 50–75 gallon tank
- Broken dip tube: The dip tube directs cold incoming water to the bottom of the tank. If it breaks, cold water mixes with hot water at the top, producing lukewarm output. Replacement costs $100–$200
- Temperature set too low: Check the thermostat setting. For most households, 49°C (120°F) provides adequate hot water while minimizing scalding risk
Strange Noises
Rumbling, popping, or crackling: Almost always sediment. As the burner heats water trapped beneath sediment layers, it creates steam bubbles that pop through the sediment — producing those alarming sounds. The fix is a tank flush: drain the tank through the bottom valve until the water runs clear. If the sediment is severe (you hear it constantly), a professional flush with a descaling solution may be needed.
High-pitched whining: Usually a partially closed valve restricting water flow, or scale buildup on an electric heating element. Check all valves are fully open. For electric heaters, element descaling or replacement resolves the issue.
Ticking or tapping: Often caused by heat traps (check valves on the inlet and outlet pipes) or thermal expansion. These sounds are generally harmless but can be reduced by installing dielectric nipples.
Leaks and Drips
From the top: Usually a loose inlet or outlet connection, or a leaking T&P (temperature and pressure) relief valve. Tighten connections first. If the T&P valve is dripping, it may be doing its job — relieving excess pressure — or the valve itself may be faulty. Either way, have a professional check the system pressure.
From the bottom: This is more serious. If water is pooling beneath the tank, the inner tank has likely corroded through. Once the tank itself leaks, repair isn’t possible — replacement is necessary. Turn off the gas/power and water supply, and schedule a replacement.
Discoloured or Smelly Water
Rusty water from hot taps only: The anode rod inside your tank has likely corroded completely. The anode rod’s job is to attract corrosive elements and sacrifice itself to protect the tank. Once it’s depleted, the tank itself begins to corrode. Replacing the anode rod ($25–$50 part, $100–$200 installed) can extend the tank’s life by several years if the tank hasn’t already begun to fail.
Rotten egg smell: Caused by bacteria reacting with the anode rod’s magnesium, producing hydrogen sulfide gas. Solutions include replacing the magnesium anode with an aluminum/zinc rod, temporarily raising the thermostat to 60°C to kill bacteria, or flushing with hydrogen peroxide. If you’re on well water, this issue is more common.
Frequently Asked Questions
How long do water heaters last?
Tank water heaters last 8–12 years on average. Tankless units last 20+ years. Regular maintenance (annual flushing, anode rod inspection) can extend a tank heater’s life to the upper end of that range. GTA’s hard water tends to shorten lifespan compared to softer water regions.
How do I flush my water heater?
Turn off the gas/power. Connect a garden hose to the drain valve at the bottom. Run the hose to a floor drain or outside. Open the drain valve and let water flow until it runs clear (usually 5–10 minutes). Close the valve, remove the hose, and turn the power back on. Do this annually.
Should I repair or replace my water heater?
Replace if: the tank itself is leaking, the unit is over 10 years old and needs a major repair ($500+), or repair costs exceed 50% of a new unit. Repair if: the issue is a thermocouple, element, thermostat, or anode rod on a unit less than 8 years old.
Is a leaking T&P valve dangerous?
A T&P valve that occasionally drips may be responding to normal thermal expansion. However, continuous dripping or discharge could indicate dangerously high temperature or pressure inside the tank. Have it inspected promptly — this valve is a critical safety device.
Need Professional Water Heater Help?
If troubleshooting your water heater points to something beyond a filter change or thermostat adjustment, book a service call or call 1-855-539-4328. H&C’s licensed plumbers diagnose and repair all water heater brands across the GTA, with same-day service available.