It’s beginning to look a lot like heating season! Whether you turn the heat on the minute the outside temp dips below 70 degrees, wait until Thanksgiving, or somewhere in between, your heating system is bound to make some noises…especially as it cycles on and off.

While some noises are perfectly normal, others may indicate that something is not quite right. Here’s a guide to 5 of the most common heating system noises and advice on when to call in a professional.

1. Banging or Clanking

In a furnace, banging, clanking, or popping could be the result of metal components expanding and contracting due to temperature changes. However, if the noise is louder than usual or more persistent, it could point to a bigger problem.

Loud banging sounds coming from a boiler are often caused by “kettling”. It occurs when there’s a buildup of sediment in the heat exchanger, which restricts the flow of water and causes it to boil. This can put undue stress on your system, potentially leading to further damage.

If you hear banging or clanking noises regularly or they are exceptionally loud, it’s time to call an HVAC technician.

2. Whistling or Squealing

A whistling or high-pitched squealing noise is often the result of restricted airflow. This can happen if the air filter is clogged, the ductwork is blocked, or there’s a problem with the blower fan. Restricted airflow can make your heater work harder than it should, resulting in inefficiency and increased wear and tear.

If replacing the air filter doesn’t quiet the noise, or if the noise persists after you’ve checked for blockages, it’s best to have an HVAC technician inspect the system.

3. Rattling

Rattling noises can be a sign of loose components in your heating system. In a furnace, this could mean that the burner assembly or heat exchanger is loose, or there could be loose screws or bolts in the blower. In a boiler system, rattling may indicate that the pressure valve is malfunctioning.

A rattling sound usually isn’t a simple issue to fix, so if you hear this noise, it’s best to call in a professional who can ensure your system is operating safely.

4. Hissing

A hissing noise can indicate a small gas or steam leak, which can be dangerous if not addressed immediately. If your heater is gas-powered, any hissing sound near the gas line or burner could signal a leak. In a steam-based heating system, hissing can also occur if there’s air in the pipes, or if the system is not properly pressurized.

If you suspect a gas leak, immediately turn off the thermostat, vacate your home, and call a the gas company’s emergency line from a safe location. If the hissing is coming from a steam system, have a professional inspect the pressure and make adjustments to prevent further issues.

5. Gurgling

In boilers, gurgling sounds are typically caused by air trapped in the system or issues with water pressure. This can happen if the system wasn’t properly bled or if there’s a buildup of debris or scale within the pipes. Over time, this can lead to more significant issues with heating efficiency and pressure regulation.

If gurgling persists, it’s time to call a professional. An HVAC technician can bleed the system, check for airlocks, and perform necessary maintenance to ensure the boiler is running smoothly.

While heating systems are designed to make some noise during operation, unusual or persistent sounds often signal a deeper problem. If you notice any of the noises described above, contact C&D Cooling & Heating right away to diagnose and resolve any issues before they escalates.