A.O Smith 40-Gallon Tall Natural Gas Water Heater (18" Diameter) - Item # 12231959 | Model # GCB-40 SIDE T&P VALVE
- 40 Gal
- Tall
- 18" Dia x 61.75" Height To Vent Connection
- Top Water Connections And Side T&P Valve
- Not Available In Specific AQMDs In CA
- DynaClean Diffuser System Reduces Sediment Buildup, Extending Tank Life
- Blue Diamond Tank Lining Provides Protection Against Leaks
- Enhanced Honeywell Gas Valve With LED Diagnostics To Ease Troubleshooting And Improve Performance
- Resettable FVIR Thermal Switch To Quickly And Easily Bring Heater Back Online
- CoreGuard Anode Rod Is Industry-Leading Anode Technology To Extend Useful Life
- Full-Flow Tamper-Resistant Brass Drain Valve
- Meets 2015 NAECA Efficiency Standards
- 0.65 Uniform Energy Factor
- 40,000 Btu
- Mfg #GCB-40 (SIDE T&P VALVE
- Water heater blanket included
- 18" Dia x 61.75" Height To Vent Connection
- Top Water Connections And Side T&P Valve
What our Experts Think
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Solid everyday performance: A classic 40‑gallon tall natural gas water heater with 40,000 BTU input and atmospheric venting delivers consistent hot water for a household of ~3 people (first‑hour ratings near ~78 gal).
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Corrosion‑resistant tank: Blue Diamond® glass lining protects the steel tank from rust, helping extend service life and reduce leaks compared with standard glass coatings.
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Sediment control for longevity: The DynaClean diffuser system helps reduce lime and sediment buildup, extending heater life and maintaining output over time.
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Diagnostics & ease of use: Enhanced Honeywell gas valve with LED status indicators makes troubleshooting and temperature control easier for homeowners and technicians.
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Durable components included: CoreGuard anode rod, full‑flow tamper‑resistant brass drain valve, and resettable FVIR thermal switch provide robust protection and long‑lasting reliability.
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Side‑mounted safety relief: Side T&P valve placement gives flexible installation options and meets standard residential safety requirements.
Q&A
Q: What household size is this water heater suitable for?
A: Ideal for households of 2–3 people, providing reliable hot water for showers, sinks, and daily use.
Q: What type of fuel does it use?
A: Operates on natural gas, delivering efficient and consistent heating.
Q: What are the dimensions of this tall water heater?
A: 40-gallon capacity with an 18-inch diameter, designed for vertical installation in utility spaces or closets.
Q: How powerful is the heater?
A: Provides fast recovery with standard BTU output for consistent hot water.
Q: Does it include safety features?
A: Yes. Comes with a temperature and pressure (T&P) relief valve for safe operation.
Q: Is it energy efficient?
A: Yes. Engineered for reliable performance with minimal energy waste.
Q: How is the tank protected from corrosion?
A: Equipped with a protective anode rod and premium tank materials for long-lasting durability.
Q: What are the installation requirements?
A: Requires natural gas connection, proper venting, and indoor residential installation
Maintenance Tips
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Flush the tank annually: Drain and flush every 6–12 months to remove sediment and maintain heating efficiency.
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Inspect the anode rod: Check the sacrificial anode rod yearly and replace if heavily corroded to prevent tank rust.
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Check gas and vent connections: Ensure gas lines, fittings, and venting are secure, unobstructed, and corrosion-free.
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Test the T&P relief valve: Operate the temperature & pressure relief valve yearly to ensure proper function and safety.
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Monitor burner operation: Watch for irregular ignition or flame changes, which may indicate venting or gas issues.
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Inspect for leaks: Regularly check water connections, fittings, and tank base for moisture or corrosion.
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Maintain proper airflow and space: Keep the surrounding area clean, dry, and well-ventilated for safe operation and easy maintenance.
Damage 
Loss 
Theft 
