• ENERGY STAR® certified with a UEF of 0.95
• Flexibility in Installation—Field convertible from natural gas to liquid propane; PVC venting flexibility (2” up to 75’ & 3" up to 150’); Install indoor or outdoor (outdoor kit sold separately)
• Save up to $116/year on annual operating costs—When compared to a standard 50-gallon atmospheric natural gas tank water heater.
• Lasts 3x Longer!—with X3® Scale Prevention Technology provides protection for the heat exchanger.
• Improved Efficiency & Reliability—Patented heavy-duty, stainless-steel heat exchanger features only two weld points and eliminates the need for a secondary heat exchanger
• Reduced Wait Time for Hot Water—Integrated recirculation pump assists in the delivery of hot water quickly (recirculation plumbing from fixture to unit required)
• Expandable for Larger Applications—Cascade up to 12 like heaters when multiple water heaters are required to work in conjunction (cable included)
• Built-in Control Display—Check status, error codes and settings and review up to two (2) recirculating schedules using the built-in display
• Optional Remote Activation—An optional kit allows the user to engage the heater to recirculate hot water at a touch of a button for on-demand, continuous hot water

The ATHR-199X3 ADAPT™+ Premium tankless water heater uses up to 199,000 BTUs of Natural Gas or Liquid Propane to deliver a max flow rate of 10.5 gal/min. A. O. Smith’s ADAPT™ premium condensing gas tankless water heaters deliver robust, on-demand performance and the flexibility to install in virtually any residential setting.

Built-in X3® Scale Prevention Technology helps maintain like-new performance by protecting the heat exchanger from build-up. Scale-prevention protection can prolong the life of the heat exchanger by up to 300% compared to an unprotected unit.

The ADAPT™ line features a built-in Control Display for setting and reviewing up to two recirculating schedules—as well as checking heater status and error codes. Manage temperature settings and activate the heater and recirculation pump remotely with optional kits (sold separately).

All models are ENERGY STAR® certified with a Uniform Energy Factor of 0.95 and comply with Ultra-Low NOx regulations. All ADAPT™ models are field convertible from Natural Gas to Liquid Propane (kit included) and can be installed indoors or outdoors with an Outdoor Vent Cap Kit (sold separately).

Cascade up to 12 like heaters together for larger applications requiring multiple water heaters to work in conjunction, cable included.

• UEF 0.95
• Maximum BTUs 199,000
• Power Source GAS
• Limited Parts Warranty 5 Years
• Water Connection Location BOTTOM
• Water Connection Size 3/4-in"
• Emissions Ultra-Low NOx
• ASME Certified No
• Amperes 5
• Destination Country US
• ENERGY STAR® Certified Yes
• Flue Diameter 2.00
• Fuel Source NATURAL
• Ignition Type Electronic Hot Surface Igniter
• Installation Type BOTH
• Limited Heat Exchanger Warranty 15 Years
• Max Flow Rate 5.9 GPM
• Minimum BTUs 9,000
• Application RESIDENTIAL
• Product Tier ProLine® XE
• Shipping Height 20.75"
• Shipping Length 40"
• Shipping Width 22.25"
• Side Loop No
• Voltage 120

Dimension & Venting

• Type Water Heater
• Height 41.8"
• Width 16.53"
• Shipping Weight 125 lbs
• Vent Material ABS, PVC, CPVC and polypropylene