When the serial number is not legible, completely missing, or you can’t figure out how to tease the year of manufacture out of the number-letter sequence, you have one more option that can help you determine approximately how old it is: the year of the ASHRAE or ANSI standard that the water heater complies with. Those acronyms stand for the “American Society of Heating, Refrigeration and Air Conditioning Engineers” and “American National Standards Institute,” and both set industry standards which are updated every few years.

   The water heater label in the photo at the top of the page complies with an ASHRAE standard for 1980. Because the serial number was still intact, we know that it was manufactured in 1985. But, if it was missing, the ASHRAE date would tell you that it could not have been manufactured before 1980. These standards get updated every 4 to 6 years, so the certification provides you with a 6-year range in which it was built: 1980 to 1986. 

The water heater in the photo above was manufactured in 1999. But, if you didn’t have a complete data plate to view, the ANSI certification (here abbreviated to ANS) would tell you that it was manufactured sometime between 1996 and 2002.

    If the yellow Energy Rating sticker is still in place, there is often a date at the bottom of it, like in the example below. 

   An experienced home inspector, one that has been looking at water heaters for years, can determine the approximate age based on the color of the tank and the logo design of the manufacturer. Rheem Manufacturing, for example, paints their tanks blue and white; but the shade of blue has changed over the years and their logo design has morphed to suit the times. A medallion like the one shown below on a deep blue tank means you are looking at a water heater that is 40+ years old.

    Also, see our blog post What can I do to make my water heater last longer?

Here’s links to a collection of more blog posts about WATER HEATERS:

• Are water heaters required to be raised off the floor? 

• Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally?

• Where are gas water heaters not allowed to be installed?  

• Is the minimum size water heater inlet pipe 1/2" or 3/4" according to the building code?

• Can you use a light switch for a water heater disconnect? 

• How can I tell if a water heater is HUD-approved for mobile/manufactured homes?

• Can you wire a 240-volt water heater with 120 volts? 

• Is it alright to have a shut-off valve on both the hot and cold water pipes at a water heater?  

• What is the minimum clearance to doors and windows for an outdoor tankless gas water heater? 

• What is required clearance for access and working space in front of an electric water heater? 

• Why is the water heater older than the house? 

• Does a water heater need a shut-off valve? 

• What does it mean when a water heater Temperature/Pressure Relief (TPR) discharge pipe is "trapped"? 

• Can I leave a gas water heater in place when remodeling a garage into a family room or bedroom? 

• Where do I find the water heater in a mobile home?

• Does a tankless water heater in an attic require a drain pan? 

• Does an electric water heater require a disconnect? 

• Is a catch pan and drain piping required for a replacement water heater?

• What is the difference between a single element and dual element electric water heater? 

• What is an FVIR water heater?

• What is a heat pump water heater?

• What is a dielectric union?

• What's that powdery crust on the pipe connections at the water heater? 

• What are the most common installation mistakes with water heater replacement?

• Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises? 

• What can I do to make my water heater last longer?

• How does a hydronic heating system work?

• What is the difference between a regular water heater and a direct vent water heater? 

• What is the difference between a regular water heater and a power vent water heater?

• What is backdrafting at a gas water heater? 

• How do I determine if a water heater is gas or electric?

• What does it mean when a gas appliance (water heater, furnace, or range) has been "red tagged"?  

• What's the valve with the flip-up handle on the water heater for?

• Why is an older water heater an insurance problem?

   Visit our WATER HEATERS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.