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A.O. Smith ProMax® Direct-Vent Water Heater

GDV ProMax Water Heater

Direct-Vent Design

  • One-pipe, dual-channel draws all make-up air from outside the home, eliminating problems caused by insufficient indoor ventilation. All units are FVIR compliant. Horizontal air intake and venting on all models up to 80 inches from outside the wall with no electrical power needed.

Intelligent Control Logic

  • The internal microprocessor provides enhanced operating parameters and tighter differentials for precise sensing and faster heating response to optimize performance.

Self-Powered Electronic Gas Valve

  • Uses a thermopile to generate the power needed to operate the electronic gas control without requiring an external power source.


  • The electronic gas control incorporates and LED status indicator that monitors system operation and service diagnostics.

Coregard™ Anode Rod

  • AO Smith anode rod that has a stainless steel core that extends the life of the anode rod, allowing superior tank protection far longer than standard anode rods.

Dynaclean™ Diffuser Dip Tube

  • Helps reduce lime and sediment buildup, maximizes hot water output. Made from long-lasting PEX cross-linked polymer.

Green Choice® Gas Burner

  • Patented “Eco-Friendly” design reduces NOx emissions up to 33% and complies with low NOx emissions of less than 40 ng/J.

Push Button Piezo Ignitor

  • Makes lighting the pilot fast and easy with one hand push button spark ignition.

Heat Trap Nipples

  • Factory-installed.

Durable Tamper-Resistant Brass Drain Valve

Blue Diamond® Glass Coating

  • An A. O. Smith exclusive provides superior corrosion resistance compared to the industry-standard glass lining.

ASME Rated and CSA Certified T&P Relief Valve

Six Year Limited Tank & Parts Warranty

Code Compliance

  • UBC, CEC, SBCC, HUD and BOCA National Codes. Meets the thermal efficiency and standby loss requirements of the U.S. Department of Energy and current edition of ASHRAE/IESNA 90.1. and meets the Federal Energy Efficiency Standards effective January 20, 2004, according to the National Appliance Energy Conservation Act (NAECA) of 1992.

Design-Certified by CSA International

  • According to ANSI Z 21.10.1– CSA 4.1 Standards governing storage-type water heaters.

Product Specifications

  • Gallon Capacity: 40
  • Recovery Gallons: 37
  • Maximum BTUs: 38,000
  • Power Source: Natural Gas
  • Energy Factor: 0.60
  • Limited Tank Warranty: 6 Years
  • Limited Parts Warranty: 6 Years
  • Anode: Standard Anode
  • T&P Relief Valve: Yes
  • Pilot Reset Button: Yes
  • Ignition Type: Electronic
  • Water Connection Location: Top
  • Water Connection Size: 3/4"
  • Emissions: Low NOx
  • FVIR Certified: Yes
  • First Hour Rating: 73
  • Height: 49 3/4"
  • Height w/Draft Hood: 64"
  • Diameter: 22"
  • Width: 22"
  • Depth: 22"
  • Shipping Weight: 178lbs
  • Vent Type: Direct Vent

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GDV-40 NG ProMax Direct-Vent Water Heater
40 Gallon, 38,000 BTU, Natural Gas
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