Smith Water Heaters. A.O. Smith is a reliable name in the water heater industry. It has come up with great innovative ideas to manufacture products that are not only high on quality but also efficient in performance.Click to see full answer. Also asked, what brand of water heater is the most reliable? The Most Reliable Water Heater Brands On The Market Rheem Water Heater. A.O. Smith Water Heater. Bradford White Water Heater. Rinnai Water Heater. Ecosmart Tankless Water Heater. GE GeoSpring Water Heater. Stiebel Eltron Water Heater. Bosch Water Heater. Secondly, how long do AO Smith water heaters last? The Lifespan of an AO Smith Water Heater Most AO Smith warranties range between 6 and 12 years, usually closer to ten. This means that the manufacturers fully expect your water heater to last at least a decade, and possibly twice that even after it goes out of warranty. Keeping this in consideration, what is the best AO Smith water heater? Best A.O. Smith Tankless Water Heaters Model Gallons/Minute Warranty ATI-540H-N 9.0 GPM 15-year ATI-340H-N 8.0 GPM 15-year ATI-310-N 8.0 GPM 15-year Is Rheem or AO Smith a better water heater?Rheem is a good, mid-level water heater brand that’s not too costly. Its reputation for manufacturing durable, reliable water heaters makes it a good choice for most homes. Overall, AO Smith is probably the better choice for gas water heaters, but only by a fraction.