Answering your search for reliable gas water heater burner replacements, this guide focuses on common, compatible burner assemblies for residential natural gas water heaters. The highlighted options are best for homeowners performing standard DIY repairs or professionals stocking replacement parts. Each product is evaluated for compatibility with standard 40–50 gallon units and for ease of installation. The top picks include high-availability brands and designs that support steady ignition and efficient flame control. This overview helps you choose the right burner assembly based on burner size, gas type, and connection requirements.
Summary table of selected products:
| Product | Brand | Gas Type | Key Feature | Amazon Link |
|---|---|---|---|---|
| 100112342 – Final Burner Assy | A. O. Smith | Natural Gas | 16″ final burner with #37 orifice | See Product Section |
| 100094001 – Final Burner Assy | A. O. Smith | Natural Gas | Final burner assembly, NAT | See Product Section |
| AM39922-1 Burner Assembly Kit | Rheem | Natural Gas | RG40S-40 burner kit | See Product Section |
| 100112351 – Final Burner Assy | A. O. Smith | Natural Gas | 18″ final burner with #37 orifice | See Product Section |
| 100093992 – Final Burner Assy | A. O. Smith | Natural Gas | Final burner assembly, NAT | See Product Section |
AO Smith 100112342 – Final Burner Assy NAT 16″ #37 Orifice
Best for standard 40–50 gallon natural gas water heaters that require a 16″ final burner with a #37 orifice. This part is designed to fit common AO Smith model ranges and supports consistent flame delivery. It is especially suitable for appliances where a precise flame pattern is needed for efficient combustion. The assembly is straightforward for technicians familiar with standard gas connections and orifice sizing.
Homeowners replacing a worn-out final burner on AO Smith natural gas water heaters, and technicians seeking a direct OEM-like fit.
Why selected: It matches the 16″ burner length and the #37 orifice, which are common on many AO Smith units, ensuring reliable ignition and flame stability.
Caution: Verify the exact model compatibility before ordering, as variations exist across AO Smith lines.
AO Smith 100094001 – Final Burner Assy NAT
This NAT final burner assembly supports natural gas units and is a solid option for standard residential water heaters. The burner assembly helps ensure proper flame ignition and distribution, contributing to steady hot water output and ignition reliability. It’s a sensible replacement when the existing burner shows signs of uneven flame or delayed ignition.
who it’s best for: Homeowners with AO Smith natural-gas heaters needing a compatible NAT final burner assembly.
Why selected: It aligns with common NAT configurations and AO Smith’s design language, reducing installation complexity.
Caution: Double-check that the model accepts the NAT final burner assembly to avoid mismatches.
Rheem AM39922-1 Water Heater Burner Assembly Kit
Rheem’s burner assembly kit is designed for RG40S-40 natural gas water heaters. It provides a complete burner portion for replacement, supporting proper gas-air mix and ignition. The kit is useful when the existing burner has worn or damaged components and a full replacement is more efficient than solving individual parts.
who it’s best for: Homeowners with RG40S-40 style heaters needing a complete burner kit replacement.
Why selected: A complete kit reduces guessing around component compatibility and simplifies installation for common Rheem units.
Caution: Ensure the kit matches the exact model and venting arrangement of your Rheem unit to avoid fit issues.
AO Smith 100112351 – Final Burner Assy NAT 18″ #37 Orifice
This 18″ natural gas final burner assembly includes a #37 orifice, extending in length to 18 inches for larger burner configurations. It’s well-suited for AO Smith models that require a longer burner element while maintaining proper gas flow for efficient combustion.
who it’s best for: AO Smith installations needing a longer final burner with NAT fuel.
Why selected: The 18″ length accommodates appliances with extended burner housings, supporting stable flame characteristics across a broader flame path.
Caution: Confirm the 18″ requirement matches your heater’s burner cavity before ordering.
AO Smith 100093992 – Final Burner Assy NAT
AO Smith’s NAT final burner assembly provides another standard NAT option for natural gas water heaters. It offers a balanced flame delivery and compatibility with typical AO Smith NAT configurations. This option is a practical replacement when the existing burner shows signs of wear or ignition instability.
who it’s best for: Owners with AO Smith NAT units seeking a straightforward burner replacement.
Why selected: It complements common NAT setups with predictable fit and flame characteristics.
Caution: Compare the burner length and orifice size to your unit’s specifications to avoid mismatches.
Buying Guide: Key Considerations for Gas Water Heater Burner Replacements
What should you check before purchasing a burner assembly?
- Gas type compatibility: Natural gas vs LP or universal options. Confirm your water heater’s gas supply.
- Burner length and fit: Ensure the correct overall length (e.g., 16″ vs 18″) to fit your heater’s burner box.
- Orifice size: Common sizes include #37; verify the proper size for efficient combustion and emissions compliance.
- OEM vs aftermarket: OEM parts tend to offer the most reliable fit; aftermarket alternatives may vary in fit and performance.
- Vent and ignition considerations: Some models require specific ignition components or venting compatibility.
- Installation complexity: Some burners are straightforward to replace; others may require removal of surrounding components or professional service.
Practical Comparison: Quick Buyer Tips
- Best for standard AO Smith NAT units: 100112342, 100094001, and 100093992 offer direct NAT configurations with familiar fits.
- Best for LED-ignition-like reliability: The 18″ NAT option (100112351) supports longer burner paths for stable flame patterns.
- Complete burner kit option: Rheem AM39922-1 is advantageous when a full kit replacement is preferred for RG40S-40 models.
- Avoid mismatches: Always verify burner length, orifice size, and gas type with your specific heater model before purchase.
FAQ
- Which burner is best for a standard AO Smith NAT water heater? The AO Smith 100094001 or 100093992 are common NAT options designed for natural-gas AO Smith units.
- Do I need an 16″ or 18″ burner? Use the burner length specified by your heater’s burner housing. Mismatched length can hinder ignition and flame distribution.
- Is an OEM burner necessary? OEM burners typically ensure exact fit and gas-flow specifications; aftermarket options may vary in compatibility.
- Can I replace just the orifice separately? Some models use a single final burner assembly with a fixed orifice; others may allow separate orifice replacements. Check your part diagrams.
- Is it safe to replace a burner myself? Replacing a gas burner involves gas supply shut-off and proper venting. If unsure, hire a licensed professional.
- Will these burners fit all Rheem units? The Rheem AM39922-1 is intended for RG40S-40 models; verify your exact model number and gas configuration before purchasing.