How to Clean a Flame Arrestor on Tank-Type Water Heaters

Understanding how to clean a flame arrestor is essential for maintaining the safety and efficiency of gas devices prone to flammable vapor risks, like tank-type water heaters.

This guide walks you through the essential process of maintaining a crucial component of the Flammable Vapor Ignition Resistant (FVIR) system in modern gas water heaters.

Keeping the flame arrestor clean not only extends your water heater's lifespan but also protects your home from potential hazards associated with flammable vapors.

flame arrestor(photo: reliance)

Introduction to FVIR Technology in water heaters

Gas tank-type water heaters are equipped with an innovative safety mechanism known as the Flammable Vapor Ignition Resistant (FVIR) system.

This system is engineered to protect households by mitigating the risk of flammable vapor ignitions, which can occur from common household substances.

The FVIR system comprises several key components, each playing a crucial role in ensuring operational safety.

Components of the FVIR System

Flame arrestor

The flame arrestor, nestled at the bottom of your water heater's gas tank, is there to safeguard your home.

Crafted from sturdy fireproof materials, it serves as a cozy blanket that keeps the flames where they belong - safely within the combustion chamber.

This clever feature is key to ensuring the warmth generated stays controlled and friendly, keeping everything running smoothly and safely in the background.

LDO Screen

The LDO (Lint, Dust, and Oil) screen, the flame arrestor's trusty sidekick, is stationed right at the air intake opening. Its job? To sift through lint, dust, oil, and any other tiny invaders, ensuring that only the cleanest air flows into the combustion chamber.

This dynamic duo works together seamlessly to keep the warmth generated by your heater clean, efficient, and safe for everyone at home.

Combustion Chamber TCO (Thermal Cut-Off)

The thermal cut-off serves as a crucial safety mechanism, engineered to automatically deactivate the heater if the combustion chamber's temperature climbs too high.

This feature is integral in preventing overheating and mitigating the risk of fire, ensuring a balance between efficient heating and safety.

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Preventive maintenance: How to clean a flame arrestor properly

To ensure the FVIR system continues to operate effectively, regular maintenance is essential. This includes:

  • Cleaning the Flame Arrestor and LDO Screen: Use a non-metallic brush and a vacuum cleaner to remove debris from the bottom part of the flame arrestor and the LDO screen. A mirror and flashlight may be necessary for visual inspection during cleaning.
  • Inspecting the Top Part of the Flame Arrestor: Accessing the top part of the flame arrestor requires removing the inner door and burner assembly. This allows for thorough inspection and cleaning, ensuring no blockage or damage that could impair the system's function.
  • Regular Inspections: Routine inspections can identify potential issues before they become serious. If any damage is found, or in the event of a flammable vapor ignition, it is advised to replace the water heater to maintain safety.

The most common problems linked to a flame arrestor

Flame arrestors are crucial for the safe operation of gas combustion appliances. However, when issues arise, they can lead to several common problems affecting both the appliance's performance and safety.

Let's explore how these issues manifest and their implications:

Poor gas combustion

This issue is often indicated by a yellow flame and sooting. Normally, a gas flame should burn blue, indicating complete combustion. A yellow flame suggests incomplete combustion, leading to soot buildup.

This not only affects the efficiency of the appliance but can also create a messy residue.

Furthermore, incomplete combustion raises the risk of carbon monoxide (CO) production. CO is a colorless, odorless gas that poses serious health risks, underscoring the importance of addressing this issue promptly.

Lack of oxygen

Adequate oxygen is essential for proper gas combustion. A flame arrestor clogged with lint, dust, or oil can restrict airflow, leading to insufficient oxygen mixing with the gas.

This situation can cause the pilot light to go out, leading to appliance shutdown. Regular cleaning and maintenance of the flame arrestor and air intake areas can prevent this problem, ensuring a stable and efficient combustion process.

High temperature in the combustion chamber

The thermal cut-off (TCO) switch is a safety device designed to prevent overheating within the combustion chamber.

If the chamber's temperature becomes too high, the TCO will trip, shutting down the appliance to prevent potential fire hazards.

This high temperature could be a symptom of restricted airflow, improper gas mixture, or malfunctioning components. Addressing the root cause of the excessive heat is crucial for the safe operation of the appliance.


Regular maintenance, including the cleaning of the flame arrestor, is vital for the safety and efficiency of your gas water heater.

Taking proactive steps to keep the flame arrestor clean ensures the FVIR system functions as intended, providing peace of mind through enhanced safety for your home and family.

Always refer to your water heater's manual for specific maintenance instructions and safety precautions tailored to your model.

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