How to Clean a Boiler in 5 Simple Steps

Keeping your heat running this winter just requires a little elbow grease

Man adjusting boiler
Photo: SolStock / E+ / Getty Images
Man adjusting boiler
Photo: SolStock / E+ / Getty Images
Nick P. Cellucci
Written by Nick P. Cellucci
Contributing Writer
Updated Dec 11, 2023
SKILL LEVEL
Simple
COMPLETION TIME
5 hours
COST
$25–$50
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What you'll need:
TOOLS
  • Bucket or pan
  • Screwdriver
  • Wrench
  • Wire brush
  • Industrial shop vac
SUPPLIES
  • Replacement air filter (optional)

If your home uses radiators for heat, you have an oil or gas boiler that needs regular maintenance. Soot builds up inside a boiler over time, causing serious problems if left unchecked. You should clean your boiler every year before winter to ensure it doesn't break and cause you to lose heat. Learn how to clean a boiler with this simple step-by-step guide.

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Angi Tip

Air duct cleaning takes an average of five to seven hours for most households. You can make the job go quicker by removing any obstacles around your HVAC entry points, like furniture, to make it easier for your pro to access the ducts.

Kassidy Barber
Kassidy Barber
Content Editor, Angi

  1. Turn Off Electricity and Fuel

    Man turning off the fuse box
    Photo: Bacho Foto / Adobe Stock

    Before you take the boiler apart, ensure your safety from electrocution or fire by turning off its electrical power and fuel supply.

    • The electrical power supply is on the boiler's main red switch plate, often located at the top of the basement stairs or near the boiler.

    • The fuel shutoff valve will either be near the oil tank for an oil boiler or near the incoming gas pipe for a gas boiler. 

    With both supplies shut off, disconnect the power and fuel lines from the boiler. Place the fuel line in a spare container, such as a bucket or pan, to catch any potential drips from the line.

  2. Disassemble the Boiler

    A man checking gas boiler
    Photo: penyushkin / Adobe Stock

    Allow the boiler to cool until it's no longer hot to the touch. This may take three hours. Once it's cool, open the vent with a screwdriver and remove the nut on the combustion chamber door with a wrench. You’ll find the combustion chamber door on the front of the boiler. Place the nut somewhere secure so you can locate it easily when it's time to reassemble the boiler.

  3. Remove Soot

    Use a wire brush to scrape soot from the walls of the combustion chamber. Soot is a byproduct of fuel and air mixing. It can be tough, and buildup can cause the chamber walls to corrode. A wire brush is strong enough to loosen any soot.

    Once the walls are soot-free, use an industrial shop vac to remove the debris.

  4. Change the Air Filter

    This step is only necessary if you have an oil-powered boiler. Oil air filters trap impurities that would otherwise clog the oil-burning nozzle, cause a misfire, and shut down the system.

    Close the oil valve, unscrew the oil filter, and swap it out for a new, clean one. Follow your local hazardous waste disposal regulations to get rid of the old filter.

  5. Reassemble the Boiler

    Man adjusting boiler in the kitchen
    Photo: SolStock / E+ / Getty Images

    Close the combustion chamber door and put the nut back on, tightening it with your wrench until it’s firmly in place. If you detached the power and fuel lines, you can now reattach them and turn the electrical power and fuel supplies back on.

     Leave the fuel valve open with your container underneath until the fuel starts flowing. This will allow any air trapped in the line to escape. Once fuel starts flowing, you can close the fuel valve and remove your container.

DIY vs. Hiring a Pro 

Boiler cleaning is a relatively simple DIY involving minimal supplies if you already own the tools. You'll pay about $35 for a replacement oil air filter and only about $25 to rent a shop vac for a few hours. However, some homeowners prefer to hire a local boiler pro.

Professional boiler cleaning costs $150 to $350. You can also pay the$200 to $500 cost for full boiler service, which includes cleaning, inspection, repair, hard water descaling, and replacement of worn-out parts. A certified HVAC pro must clean certain boiler system parts, such as the burners, coils, draft hood, and chimney.

Frequently Asked Questions

To maintain a boiler and ensure it works optimally, regularly read the temperature and pressure gauges on the unit to ensure they're within the limits described in your owner's manual. Lubricate the circulating pump according to the manufacturer's instructions. Check the water level in the expansion tank and open the tank valve to drain it if it's more than half full.

If you don't clean a boiler, you may have higher energy bills or no heat. A dirty boiler is inefficient and can't properly maintain a heating system. It may break down more often due to corrosion or clogs from soot and oil buildup. Cleaning a boiler improves its performance. The cost to replace a boiler can be expensive, so keeping it clean is a cost-effective practice.

If you’re unsure who to call to fix your boiler, you have a few options. One is to call a dedicated boiler service. However, you can also call a plumber or HVAC technician for boiler repair services. These pros will have the tools, knowledge, and experience to fix common boiler problems.

The key difference between a heat pump vs. a boiler is the type of heat they produce. A heat pump produces heat more slowly, with a smaller temperature difference. The lower temperature of a heat pump requires a convector with a large surface area. A boiler, on the other hand, produces a lot of high-temperature heat and emits it through smaller radiators.

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Learn more about our contributor
Nick P. Cellucci
Written by Nick P. Cellucci
Contributing Writer
Nick has been a copywriter in the home services industry since 2017, marketing for hundreds of flooring and home improvement providers throughout North America.

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