Your furnace just stopped working in the middle of a cold Toronto night. You hear strange banging coming from your basement. Your water heater is leaking all over the floor.

When something goes wrong with your home’s heating, cooling, or plumbing, you need answers fast. That’s where these noise guides come in. We break down what’s normal, what’s fixable, and when you need to pick up the phone and call for help.

Popping or Rumbling Sounds

This is the most common water heater noise GTA homeowners hear. It sounds like popcorn popping or distant thunder coming from your tank.

What causes it: Sediment buildup at the bottom of your tank. Over time, minerals in Toronto’s hard water settle and harden on the tank floor. When your burner heats the water, it has to burn through that sediment layer, causing the popping sound.

Is it serious? Not immediately, but sediment reduces efficiency and can eventually crack your tank. If you’re hearing this regularly, it’s time for a tank flush or inspection.

What to do: A professional can drain and flush your tank to remove the sediment. If it’s been years since your last flush, this should be done soon. Left too long, the sediment hardens and becomes impossible to remove.

Hissing or Sizzling

A hissing sound often means water is dripping onto hot surfaces or there’s a leak somewhere in the system.

What causes it: Water leaking from the temperature and pressure relief valve, a loose connection, or condensation dripping onto the burner.

Is it serious? Yes. Any leak needs attention fast. A failing pressure relief valve is a safety issue that shouldn’t be ignored.

What to do: Check around your water heater for visible water. If you see moisture or dripping, turn off the water supply and call a plumber immediately.

Knocking or Hammering

This sounds like someone banging on your pipes when the water turns on or off.

What causes it: Water hammer. When water flow stops suddenly, it creates a pressure wave that makes pipes bang against walls or supports. This isn’t usually the water heater itself, but the plumbing connected to it.

Is it serious? It can be. Repeated hammering can damage pipe joints and connections over time.

What to do: A plumber can install water hammer arrestors or adjust water pressure to fix this. It’s worth addressing before it causes leaks.

Screeching or Whistling

High-pitched sounds usually point to restricted water flow somewhere in the system.

What causes it: Partially closed valves, sediment restricting the inlet or outlet, or issues with the pressure reducing valve.

Is it serious? Moderate concern. Restricted flow reduces hot water availability and puts extra strain on the system.

What to do: Check that all valves are fully open. If the noise continues, have a plumber inspect the system for blockages.

Humming (Tankless Water Heaters)

A low humming during operation is normal for tankless units. But if the humming gets louder or changes pitch, something’s wrong.

What causes it: Normal operation, but loud humming can mean loose components or water flow issues.

Is it serious? Only if it’s new or getting worse.

What to do: Have a tech inspect and tighten any loose parts.

When to Call a Professional

Call immediately if you notice water pooling around your heater, smell gas (rotten egg smell), see rust-colored water, or hear loud banging that shakes the unit. These are signs of serious problems that can lead to flooding or safety hazards.

For sediment buildup, strange but not urgent noises, or if your water heater is over 10 years old and starting to act up, schedule an inspection soon.

Need Water Heater Help?

Accurate Air Plus handles all water heater repairs and replacements across the Greater Toronto Area. Whether it’s a strange noise, no hot water, or time for a replacement, we’ve got you covered.

Call us today for fast, reliable plumbing service.

Accurate Air Plus. Your trusted HVAC and plumbing experts serving the GTA