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Strange Furnace Sounds

Hearing popping noise from your gas heater can be concerning. You may wonder, why is my gas heater making a popping noise? There could be several reasons. Dirty furnace burners or damaged air ducts are just a few.

Read on for some likely reasons your gas heater makes a popping noise, strange furnace sounds from your heating system, how to silence your HVAC System, and when to call for furnace repair or replacement.

Why Your Gas Heater Makes Popping Sounds

Interestingly, both gas-fired and electric heaters can emit popping noises. Here are the reasons your gas heater may make popping sounds.

Accumulated Dirt on Furnace Burners

Your furnace burners could accumulate dirt over time. Consequently, there will be a delay in the ignition carrying through. In turn, gas will build up in the furnace. Built-up gas in the gas heater causes it to emit a loud pop or bang when the gas igniter finally works.

The effect on the furnace can be damaging like the cracking of some components. If the problem is not addressed immediately, you may be forced to do hefty repairs. Thus, it is vital to conduct routine inspections and preventive maintenance of your gas heater.

Metal Ducts Expanding and Contracting

Likewise, if your gas heater has air ducts made of metal, the popping sound could be because of damaged air ducts. The vents send warm air throughout your home. The metal ducts expand and contract as the furnace turns on and off.

But, if there is a faulty component, the metal may make a loud banging or popping noise when expanding and contracting. These defective components may include closed vents, flimsy ducts, undersized ducts, or clogged air filters.

You can reduce the noise from ductwork. Simply replace rectangular ducts with round ones. Similarly, you can use thicker metals to replace very thin ones.

Loose Inducer or Fan

A popping sound can arise from a loose fan in operation. For oil-powered furnaces, a motor-powered fan or inducer blows out smoke and fumes. In addition, accumulated dirt can hinder the fan’s operation. If this problem arises, invite a heating repair professional to check it out.

Worn Out Furnace Motor Bearings

Similarly, with use, bearings in the furnace motor may get worn out. This can result in popping noises.

Faulty Gas Valve or Pilot Light Assemblies

Furthermore, popping noises from your gas heater could be due to gas valve or pilot light problems. A problematic gas valve may need fixing by a professional. Likewise, worn-out, bent, or loose pilot light assemblies are indicative of internal malfunctioning and should be adequately checked.

Minerals in the Water Tank

Your gas-fired water heater making popping noises could be because of the scale at the bottom of the tank. Usually, mineral deposits are present in spring, well, and municipal water systems. Water can carry these minerals when running through the ground. The heat from the water heater causes air bubbles to form and drift upward.

It also makes minerals such as calcium and limestone fuse together, creating flakes or chunks. The air bubbles bump the minerals. In turn, the minerals strike the side of the tank and emit popping sounds. Thereafter, the minerals drift to the bottom of the tank as the water cools off between each heating cycle. However, the process is repeated during the next heating cycle.

Here are some options to rid your tank of accumulated mineral deposits.

Flush the Tank

Periodically, you can flush the tank. Begin by draining the tank completely. Next, let in a flow of freshwater through the tank. Thereafter, refill the water heater. Next, turn the gas and cold water supply off. Allow the tank to cool off for some hours. Then, attach a garden hose to the drain valve and drain the tank.

You may see some clumped mineral deposits. You can dispose of them. Finally, run water through the tank once more to remove all the minerals. Now, you can close up, refill the tank, and fire up the burner.

Use a Water Softener

Alternatively, use a water softener to filter out mineral deposits. This works for very hard water. Ultimately, the soft water causes little or no popping noises inside water heaters. However, the installation should be done by a licensed plumbing professional.

Faulty Pressure Relief Valve

Is the sound more like that of a boiling pot than like the popping sound of an old coffee pot? It could be due to a faulty pressure relief valve. Therefore, it is a severe problem. Pressure relief valves are safety features for hot water heaters. They let off steam from the tank. As such, if the valve is faulty, the steam builds up pressure inside the tank. Ultimately, the tank can rupture. That is why upon detecting boiling sounds, it is recommended you call a plumbing professional.

Poor Mix of Combustion Air

Try to identify the individual burner giving the popping sound. The air supporting combustion air to the burner could be improperly mixed. As such, opening the air shutter just a little bit would increase the popping noises.

An insufficient air supply would result in a weak flame, while a rich air supply would deliver a yellow flame.

The air shutter of your gas burner is likely located at the end of the burner tube closest to the supply manifold. Remember to re-tighten the screws after your adjustments.

Broken or Unstable Blower Wheel

A broken furnace blower wheel is a serious problem. You will hear furnace sounds like pieces of metal scraping together. The repair and replacement process could involve replacing this part of your furnace.

Similarly, the furnace sounds could be like a washing machine that is out of balance. A piece of tissue or other material is likely being sucked into the return air duct. The result is the blower wheel going off balance. In this situation, the entire HVAC system could be compromised.

Cracked Heat Exchanger

Popping sounds from your furnace could be a result of a cracked heat exchanger. The constant heating and cooling off process can cause cracks and lead to the emission of carbon monoxide into your indoor space.

Strange Furnace Sounds From Heating Systems

Many people complain of loud or strange sounds coming from their furnaces when it comes to heating repairs. Some of the sounds are pretty normal. However, others may give you a reason to call in a technician.

Here are some strange furnace sounds and their implications for water heaters or heating systems.


Usually, you can hear a loud bang when the furnace comes on. It indicates a problem with the ignition system. The thermostat has given the signal to the furnace to start a cycle. The gas valve is open, but the pilot light or ignition system does not ignite the gas immediately. Some amount of gas builds up in the combustion chamber.

Finally, a loud banging or popping noise is created when ignition occurs due to the gas build-up.

The ignition system could be affected by several things. First, a weak flame can slow the ignition of the gas. Second, clogged or dirty burners might be the cause. In addition, low gas pressure could delay gas ignition until gas builds up in the chamber. Again, you should invite a trained technician to check and repair this issue.


There is interference with airflow if you hear your furnace whistling. A dirty or faulty air filter could be responsible for the sound. Similarly, closed vents, blocked return, or objects in the ductwork can cause strange sounds.

Cleaning the ducts, filter and returning and opening up the vents can help resolve this issue. On the other hand, your furnace may be too big for your ductwork or blower, or burners could have problems. Calling a technician is better in these instances.

Clunking or Knocking

Knocking noises are often caused by fan issues. The blower fan could be misaligned, causing it to hit the walls or other parts of the furnace. Likewise, the fan belt could be split or cracked. In either case, turn the furnace off and call a technician.


A problem with the burner can turn a gentle whoosh of your furnace into a low or loud rumble when it powers on. Burning fuel due to oil or gas remaining in the combustion chamber can lead to rumbling noises too.


When the usual hum of an igniting burner changes to a loud humming sound by the inducer motor, it could be faulty. Moreover, your fan could be wearing out. When the loud hum occurs all day, it is vital to call in a technician.

Screeching or Scraping

Does the screeching sound like pieces of metal are being dragged across each other? The blower fan may be loose. Consequently, the blades could be dragging across the furnace casing. The scraping noise could also be because of additional furnace parts loosening. It is recommended to turn the furnace off and have a technician inspect it.

How To Silence Your HVAC System

You can resolve noisy heating systems or furnace noises with some quick fixes. Here are a few such HVAC repairs.

  • Make sure to change out your air filter at least once per season. They can become dirty and clogged, causing whistling noises.
  • Perform regular preventive maintenance. Regular maintenance can involve a technician adjusting and cleaning parts of the furnace.
  • Examine vents and dampers. Closed vents or dampers can restrict airflow and cause whistling noises. Slide them to an open position if needed.
  • Check air ducts. Loose joints, dents, or too much space between the ducts and vents can produce loud popping or banging noises. Tighten or seal loose areas with duct tape.

When To Go For Furnace Repair Or Replacement

Strange noises in heating systems can include rattling noises, loud bangs, boom, rumbling, screeching, or knocking. It may call for a repair or replacement. What does the process entail? Usually, a qualified gas plumber will do an inspection of the heating system. After that, the technician might recommend gas heater repair or replacement.

It would be advisable to have maintenance plans in place as a preventive measure. For instance, duct cleaning is an excellent preventative maintenance process that should be done regularly.

Seek Professional HVAC Maintenance And Repair

There are professional companies that have good HVAC technicians to provide these services. More so, they offer good heating and air conditioning solutions. This means that they can advise you on solutions for better indoor air quality, air handlers, air purifiers, ac repairs, and ac installation. Moreover, they may be able to provide options for ductless systems such as ductless mini-splits.


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