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Tankless with X3® Scale Prevention Technology

X3® Scale Prevention Technology prevents scale build-up, meaning virtually zero lifetime descaling maintenance and three times longer product life. Now available on our suite of condensing gas tankless water heaters.

High-Efficiency Condensing Gas Tankless Water Heaters

X3® Scale Prevention Technology

Scale is the #1 enemy for tankless technology. With normal use, typical gas tankless water heaters begin to scale up over time. Scale reduces efficiency and increases annual cost of operation. Regular descaling is required to keep typical gas tankless water heaters operational, leading to ongoing maintenance costs. 

An expert in both water heating and treatment, A. O. Smith has combined the two technologies to achieve unparalleled protection on our existing 540, 340 and 240 condensing gas tankless models. X3® Scale Prevention Technology prevents scale build-up, meaning virtually zero lifetime descaling maintenance and three times longer product life. Now available on our suite of condensing gas tankless water heaters. 

Benefits of Gas Tankless Water Heaters with X3® Technology

Extends Life Up To 3 Times Longer

The new X3® Scale Prevention Technology eliminates particle build-up in the heat exchangers, preventing scaling and extending the life of the unit. 

Maintains Like-New Performance

Tests showed tankless models with X3® Scale Prevention Technology maintained like-new efficiency after 15 simulated years vs. models without X3® technology showed 10% efficiency reduction in just 1.5 years.

Never Descale Again. Ever.

X3® Scale Prevention Technology eliminates the need for regular scale-related maintenance as it prevents scale from ever building up.

"Peace of Mind" Scale-Inclusive Warranty Coverage

A. O. Smith stands behind this revolutionary product with the industry’s first ever “Peace of Mind" limited warranty. Unlike competitive warranties, this 15-year limited warranty covers scale-related failures should they occur.

Get Instant Hot Water

Tankless with X3® Scale Prevention Technology are recirculation pump capable with the use of a cross-over valve available through APCOM. Cross-over valve sold separately.

Rebates & Tax Credits

Up to $850 in Local Utility Rebates may be available in your area!

*Gas water heaters with UEF of 0.82 or higher OR with a thermal efficiency of at least 90%. Local utility rebates available in limited geographical areas. For information on the Federal Tax Credit, go to: Check with your tax advisor for applicability. Offer details and expiration may vary. See Rebate Center for details.

How it Works

Adapt gas tankless water heater cutaway showing internals

How X3® Scale Prevention Technology Eliminates Scaling Problems

Condensing gas tankless water heaters with X3® Scale Prevention Technology are attached directly to the water line. When you open a hot water tap, the burner in your gas tankless water heater activates. As water flows through the unit, it quickly reaches the preset temperature by rapidly absorbing heat from both heat exchangers. Our patent pending X3® Scale Prevention Technology allows mineral particles to pass through harmlessly while also continually protecting the heat exchanger from scale buildup. This eliminates the need for regular descaling and extends the unit’s life up to three times vs. a tankless model without X3® Scale Prevention Technology.

Due to this direct heat exchange, these condensing gas tankless water heaters provide long-lasting, on-demand hot water. When the water tap is turned off, the unit shuts down to conserve energy.

Still Have Questions?

The Gas Tankless with X3® Scale Prevention Technology has been tested in various locations around North America, including Roswell, New Mexico, an area with some of the hardest water in the country, to ensure its performance can hold up in the harshest water conditions.
Yes, our tankless models with X3® Scale Prevention Technology are capable of being used with a recirculation pump when a cross-over valve is used. Cross-over valve sold separately.
Residential single-family applications with hard water concerns. Hard water is everywhere. In fact, more than 85% of American homes have hard water which adversely affects plumbing systems, including water piping, water fixtures and the water heating system.
No, currently the 540X3, 340X3 and 240X3 models are designed for use in residential single-family applications where Easy-Link™ is not required.
Based on our research, stainless steel and copper heat exchangers fail at the same rate due to scale build up. That’s why it’s important to install an A. O. Smith tankless model with X3® Scale Prevention Technology.
Because this is our standard condensing gas tankless model that you’re already used to, they are compatible only with 3�? or 4�? venting. As long as the gas line is sized appropriately for the BTUs, ½" gas lines can be used based on national fuel gas codes or applicable local gas codes or as outlined in the instruction manual.
The 340X3 and 240X3 models come standard with a pressure relief valve. The 540X3 does not currently include a pressure relief valve.

Product Comparison

Adapt XE
Adapt XE Premium Condensing Gas Tankless with X3® Scale Prevention Technology
ProLine® 50-Gallon Gas Water Heater
Adapt™ XE Natural Gas Premium Condensing Tankless Water Heater with X3® Technology
ProLine 50-Gallon Atmospheric Vent Tall Gas Water Heater
Single Shower Length
37 minutes
Showers back-to-back
4.7 showers
Showers at the same time
3.1 showers
3.2 showers
Maximum Tube Size
87 gallons
X3® Scale Prevention Technology
Continuous hot water
Space savings
Energy Efficiency
Hot Water Storage Supply
15 years
6 years

Many factors affect the actual performance of a water heater. This represents our closest approximation of your likely experience with this water heater in your local area, but actual performance may vary depending on factors beyond our ability to control or estimate.

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Why A. O. Smith?

Market Leader

A. O. Smith is a leading manufacturer of both residential and commercial water heating technologies, including the #1 most specified commercial water heater.

Commitment to Innovation

For more than 145 years, we’ve developed state-of-the art products that push new boundaries and improve the lives of our customers.

Best-In-Class Support

We combine cutting-edge technology with committed people who take pride in providing the very best support for our customers.

Unmatched Quality

Our products are put through rigorous quality and endurance testing so now matter where hot water is needed, A. O. Smith can provide a solution you can count on.

Learn more about A. O. Smith