AO Smith Direct Vent
Water Heaters
Review and Buying Tips

A review of the AO Smith direct vent water heaters, designed for heating potable water in residential and mobile homes. Explore the differences, features, specification and available models. What you should know when installing the direct venting system.

AO Smith Company, from its extensive line of gas water heaters, offers two groups whose models are using direct venting: ProMax Specialty Vent and Energy Saver. Other groups, such as standard Promax, Vertex, Effex and the most popular Conservationist utilize only atmospheric and power venting.

AO Smith direct vent water heaters do not require electric power to move the fresh air in, and products of combustion out; it is done by utilizing the sealed combustion chamber and the co-axial venting system (a pipe inside the pipe). The outer pipe is used to take the air directly from outside, while the inner pipe moves the flue gases out. As you can see the greatest advantage of the direct vent models is that they eliminate the problems caused by the insufficient indoor ventilation.

AO Smith direct vent water heater

ProMax Specialty Vent

ProMax Specialty Vent series offers two types of direct vent models; ProMax Direct Vent and Side Loop Direct Vent.

ProMax Direct Vent

AO Smith direct vent water heaters from ProMax series are high recovery models, equipped with several exclusive features.

DV models are FVIR compliant, which means there is no accidental fire caused by the presence of the flammable vapors.

Green Choice gas burner is environment-friendly as it produces less greenhouse (NOx) gases than the standard type.

The metal tank is protected from the aggressive water action as the unit uses the protective CoreGuard magnesium anode rod with the stainless steel core.

DynaClean system is specially designed diffuser or dip tube that creates the turbulent incoming water stream to reduce the mineral deposits, which keeps the efficiency high and maximizes its output.

The ProMax direct vent models are using one co-axial, horizontally installed pipe with the length of up to 40 ft.

Water heaters are available in three sizes all with the 6-year warranty on the metal tank and most of the unit's parts:

Model Gal. First Hour
Delivery (gal)
GDV-40 40 73 41 0.62
GDV-50 50 87 45 0.60
GDVT-50 50 88 55 0.59
GDV-75 75 131 60 0.59

From the four models above, two are coming with the 50-gallon tank size, where the GDVT-50 model has more power, 50,000 vs. 42,000 BTU, so the recovery rate and FHR are better.

ProMax Direct Vent Side Loop

AO Smith direct vent water heaters from ProMax series are also built with the side loop so that they can be used in combined space and potable water heating applications and systems with the recirculation. They still come with the popular and quality features as the above direct models: CoreGard anode, Green Choice burner, dual-channel venting, Blue Diamond glass coating...

One of the most significant features is its small microprocessor, which improves the heater's performance and gives you more comfort by controlling the gas burning better.

The gas control valve is using the thermopile which makes the valve self-powered (no electricity needed) and has the LED indicator to monitor the process with the option to signalize when there is a problem with the unit.

Three models are in use:

Model Gal. First Hour
Delivery (gal)
GDV-40L 40 73 41 0.62
GDV-50L 50 88 55 0.59
GDV-75L 75 131 60 0.57

Energy Saver

Energy Saver series includes direct vent gas water heaters that are designed for manufactured housing that complies with the FVIR and HUD requirements.

They are factory built to use natural gas, but the gas control valve can be easily adapted to use propane.

As opposed to the residential models, AO Smith direct vent water heaters for mobile homes draw all the combustion air from outside by using the bottom intake air vent.

The manufacturer recommends using the approved roof jack kits, sold separately for moving the exhaust gases out.

Model Gal. First Hour
Delivery (gal)
FMD-30 30 54 31 0.61
FMD-40 40 64 33 0.59
FMD-50 50 77 39 0.59

Every direct vent water heater from AO Smith must be installed per codes and manufacturer's instructions to keep the water heating process reliable and safe and warranty valid. Moreover, by maintaining the unit regularly and correctly, your water heater will last for many years.


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