Understanding Water Heater Date Codes

[hausdok]

Though water heaters are relatively inexpensive compared to the price of a house, repairs for the damage caused when one suddenly has a catastrophic failure is likely to be expensive. This is the reason many inspectors want to at least be able to give their client some idea of how old the device is and when it would be a good idea to start considering replacement.

So, what exactly is the absolute maximum service life to expect? It varies from place to place and is affected by the quality of the product, minerals/chemicals in water, the amount of maintenance the water heater receives and usage. In other words, there is no set in concrete maximum expected service life. In fact, two neighbors with exactly the same brand of water heater installed on exactly the same day on the same street in identical houses can have completely different experiences. In some parts of the country it is normal to expect between 10 and 15 years, while in others a homeowner is lucky if the water heater lasts 10 years.

The manufacturing date is coded into the serial number of water heaters and, since there are more than 100 different brands of water heaer in this country, the thought of trying to memorize every single serial number code at first seems impossible. Impossible that is, until one realizes that only six manufacturers produce those 100+ brands and some share the same basic method for coding, making the task of memorizing the coding methods far less formidable. In this article I'll explain the coding method used by each of the six major manufacturers. At the end of the article, there's a link to a handy decoding chart in TIJ's downloads library.

American Water Heater Company

American Water Heater Company, manufacturer of 52 separate brands of water heaters, uses a 10-digit serial number with a year/week code in the first four digits of the serial number. The year of is the first two digits followed by the two digit week of the year. For example,the serial number 0602****** indicates that the water heater was manufactured the second week of 2006. A complete list of brands manufactured by American is contained in the decoder chart linked to this article.

A.O. Smith Corporation

Prior to 2008, A.O. Smith Corporation, manufactured three brands of water heaters - A.O. Smith, Glascote and Perma-Glas - and used a 10-digit serial number with a letter-month/year code in the second third and fourth digits of the serial number. With this system, the letters A to M, excluding the letter I, are used to designate the months 1 to 12 followed by the two digit week. For example,*H06****** would indicate that the water heater was manufactured in February 2006. In 2008, A.O. Smith acquired State Industries and since then has used the State Industries sequencing (see below).

Bradford-White Corporation

Bradford-White manufactures two brands of water heater - Bradford-White and Jetglas - and uses a 9-digit letter/number code with two letters signifying the year and month of manufacturer. The letters I, O, Q, R, U, and V are skipped to produce 20-year cycles. These cycles began in 1964 with the letter A, therefore the letter A in the first position of a B-W serial number can represent the years 1964, 1984 or 2004. B-W's second letter corresponds to the month of the year as with the A.O. Smith example above.

Prior to 1973, the month letter was placed at the end of the 9-digit serial number but from 1973 on it has been in the second position. For example, the serial number B********D indicates the water heater was manufactured in April of 1965 but the serial number BD******* can indicate that it was manufactured in April of 1985 or 2005. The trick is being able to distinguish the age of water heaters with the same date codes manufactured after 1973. Fortunately, most home inspectors can do this easily simply by checking the large yellow energy usage tag on the unit to see which ANSI date is posted there. There is one exception to B-W's serial number code that was caused by a computer glitch when some units were manufactured with a serial number beginning with OA - O being one of the numbers that is not used. Any found with a serial number beginning with OA will have been manufactured in January of 1997.

Lochinvar Corporation

Lochinvar Corporation only manufactures four brands of water heater - Lochinvar, Energy Saver, Golden Knight and Knight - and uses the identical dating code system used by Bradford-White Corporation.

Rheem Corporation

Rheem Corporation manufactures 20 different brands of water heater and uses two different serial number series - one that is all numbers and the other which is both letters and numbers. However, the date code is based on the first 4 digits of the serial number, which signify the month followed by the year, the letter, which is in the 5th position, doesn't need to be considered. For example, any Rheem manufactured product bearing the serial number 0794****** or 0794F***** will have been manufactured in July of 1994.

State Industries

State Industries was acquired by A.O. Smith in 2008. Prior to becoming part of A.O. Smith, State manufactured 23 separate brands of water heater, including the Kenmore(Sears) brand, and used a letter-month/year serial number code similar to the A.O.Smith model with the letter signifying the month, followed by a number for the year. The difference is that with these the code is in the first three positions of the serial number, not the second, third and fourth as A.O. Smith does it, therefore a serial number C05******* indicates that the water heater was manufactured in March of 2005. After the 2008 acquisition, State began coding the date into the first four digits of the serial number - the two digit year followed by the two digit week; therefore 0912 is the 12th week of 2009.

There are other brands of water heaters being sold in this country that are not made by one of these 6 manufacturers. However, these 100+ brands are supposed to comprise the overwhelming majority of residential water heaters sold in this country today. Once one understands how these serial numbers work and learns to recognize each of the six manufacturer's individual patterns, it's much easier to feel confident that he or she is providing the customer the correct information about the age of the appliance.

To download the newly revised decoder chart, click here for a pdf version and here for a MS word version.

[gvk]

Thanks for the great information.

Do you have any information on the John Woods or John Woods Pro brand?

These may only be Canadian brands, but I can't find any written information.

Thanks .... Sean

[hausdok]

Hi,

Well, it took me a few minutes to figure out but I think I've got it. Believe it or not, it was a CPSC recall that helped me do it. There is a recall notice for controls on GSW (John Woods) water heaters that involve those sold from February 2002 to April 2003 and it involves GSW water heaters with serial numbers from 0202694162 to 0304507825 (underlining is mine).

Based on that, I've surmised that they use a two digit year followed by a two digit month so the 0202 in that first serial number equals Feb 2002 and the 0304 in that second number equals Apr 2003, which is exactly what the recall says. That should do it for you.

Looks like maybe I have to start compiling a list of Canadian brands as well. Hey you Canadian folks, send me some Canadian brand names and examples of their serial numbers so I can begin compiling a chart for Canada too.

ONE TEAM - ONE FIGHT!!!

Mike

[gvk]

Thanks for the speedy info. I will have a look when I get back home.

I had always heard that the year / month coding had stopped in 2000, but you have proved that wrong. As for the Canadian brands that I routinely see......

John Woods 90%

Sears/Kenmore 5%

Other 5%

They must have some good marketing up here.

Thanks again for the information.

Sean O'Brien

GVK Home Inspections Ltd.

604-839-4301

gvk@shaw.ca

www.gvkhomeinspections.ca

[monte]

Mike,

Good information, I really like the decoding chart.

[hausdok]

Hi All,

I've revised the code chart to make it a little easier to understand and in the next day or two will be replacing the one linked above with the new chart and that one will show the grid lines better. In the meantime, I've had such a good response to this one that I've decided to try and do something similar for heating systems and I'm looking for help from everyone. What I need is pictures of serial number plates for various manufacturers along with an explanation, if you have one, of how they are coded. If you don't have photos but can write out the code like I did on the chart, say ****A95**** or something similar I'd appreciate it. If you're willing to help, send whatever you've got to hausdok@msn.com and I'll see if I can create a similar chart for HVAC systems.

ONE TEAM - ONE FIGHT!!!

Mike

[StephM]

Hi there, I came across this article while Googling for info on how to tell how old a water heater is. It's so confusing that it had me thinking it was from 1994 and by using the info I found on this post I found out it's actually from 2007!!!![:-bigeyes That's a HUGE difference. So I just had to drop a line and say Thank you very much.[^]

[kciggster]

I have a Gas Water Heater that states it was manufactured by State Stove and Manufacturing Co in Henderson, NV. The Model# is C4 40 TMH. The serial# is K75100124. Does this mean the water heater was manufactured in October of 1975? The reason I ask is that my gas bills are high in the summer months and when we take showers the hot water only lasts about 10 minutes. I spoke to the gas company and they said the problem is likely the water heater. The only other gas appliances we have are the furnace (which isn't used in the summer) and a gas stove (which isn't used that much in the summer because I BBQ). Should the water heater be replaced?

Thank You

[hausdok]

Hi,

Yes, it's very old - 34 years (K is September, not October (They don't use the letter I). Those things have an expected service life of about 10 to 15 years from the date of installation when properly cared for. It sounds like you've probably either lost one element or the dip tube has broken off - either way, it should have been replaced a couple of decades ago.

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

State Stove and Manufacturing Co. became State Industries in 1974.

Mike, which "lost element" of a GAS water heater would result in a higher GAS bill? (can't find the smilie of an old, senile dude in Depends).

[hausdok]

Jeez,

I must be getting black holes in my reading to have missed that. Crimeny, how embarrassing. I just crapped my Depends. [:-paperba

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

I'm only messin' with you 'cuz you can't kick my ass from 2800 miles away.

[hammerwammer]

I clicked on that link and found Furnace info but not Water Heater, my computer skills aren't great so i have to ask, thanks for any help.

[tonybridgens]

Thanks for the speedy info. I will have a look when I get back home.

I had always heard that the year / month coding had stopped in 2000, but you have proved that wrong. As for the Canadian brands that I routinely see......

John Woods 90%

Sears/Kenmore 5%

Other 5%

They must have some good marketing up here.

Thanks again for the information.

Sean O'Brien

GVK Home Inspections Ltd.

604-839-4301

gvk@shaw.ca

www.gvkhomeinspections.ca

[tonybridgens]

I have just had the pleasure of replacing a leaking hot water tank serial 9412....so Dec '94. I asked the installer where is the plug for accessing the anode? Eventually we found it, located under the power vent unit which therefore has to be removed in order for an anode to be replaced. I phoned the manufacturer of the replacement unit to complain the anode access on it was also hidden under the vent fan unit. They said they were in no hurry to change the design because they would have to modify their die to stamp out another hole. By the way, you can't simply rotate the fan unit because they run wires down the anode access hole. Bye Bye $1600 !! I would have replaced the anodes, they are $35 and easy to get in the hardware store. I use them to protect the galvanized legs on my dock, they also seem to keep zebra mussels off.

[brodiehavelock]

Hi,

it's a great information that i can read it...There have been many people who have used Rheem hot water systems in their homes. With this, they have appreciated how much money they were able to save when they switched to using this brand. Because they were also able to heat water in a lesser time than before, they no longer have to wait for such a long while before they can start using them. []

[hausdok]

I have just had the pleasure of replacing a leaking hot water tank serial 9412....so Dec '94. I asked the installer where is the plug for accessing the anode? Eventually we found it, located under the power vent unit which therefore has to be removed in order for an anode to be replaced. I phoned the manufacturer of the replacement unit to complain the anode access on it was also hidden under the vent fan unit. They said they were in no hurry to change the design because they would have to modify their die to stamp out another hole. By the way, you can't simply rotate the fan unit because they run wires down the anode access hole. Bye Bye $1600 !! I would have replaced the anodes, they are $35 and easy to get in the hardware store. I use them to protect the galvanized legs on my dock, they also seem to keep zebra mussels off.

I don't know why you would be attempting to replace the anode rod in a 17-year old water heater. A conventional tank type water heater that old is probably already beyond saving anyway.

ONE TEAM - ONE FIGHT!!!

Mike

[Peace Citizen]

Incorrect Information: Bradford White Water Heaters

We recently had a home inspection prior to the sale of our house and going through the report we found the inspector had listed that our W/H was manufactured in 1991 and was well outside the warranty.

This caused us some stress, because we had just had the W/H installed less than a year ago and were under the belief it was a brand new unit, which we had paid full price for through our contractor.

After finding your site and checking the age ourselves we found that with a Bradford White unit the first two letters (of the 9 digit serial #) designated a unit made after 1973, but were in 20 year cycles starting in 1964. The first letter being a G (the 7th letter), this placed our W/H in either 1991 (as noted by the inspector) or 2011 which would be after our install, so impossible.

After noticing that our serial number was 10, not 9 digits and looking to start calling our contractors, we called Bradford White.

The woman who answered in the warranty department, instantly knew the unit was made in 2010! Based on the first two letters and the fact there were 8 digits that followed (meaning a newer unit).

So there is some issues with the information on this page concerning this issue and it seems there are inspectors operating with this same bad information.

A call to the manufacturer and an update of this site should be in order, as there obviously been some changes in serial number coding for at least one W/H manufacturer.

Thank you.

[hausdok]

Hi,

I'm not sure I understand what you are calling wrong - us or the Bradford-White site.

If you are referring to our chart and the information listed on it for B-W you read the chart wrong. If the first letter of the serial number on your water heater is a G, our chart says that the water heater was manufactured in 2010. The inspector, and you, made a mistake. Look below and then reread the B-W info on the chart.

2004=A

2005=B

2006=C

2007=D

2008=E

2009=F

2010=G

2011=H

B-W uses the first two places for letters that designate the year and then the month. They could have 100 digits and the first two places, the letters, still designate the year and month.

It's a simple mistake. I made it myself until I wrote down the years as shown above and placed the letters next to them.

Don't believe me? Go to the B-W site. Click here and look for yourself.

By the way, tell the inspector to stop by here and download the most recent revisions to the chart which I posted last week. They are here.

ONE TEAM - ONE FIGHT!!!

Mike

[Peace Citizen]

Originally posted by hausdok

Bradford-White Corporation

Bradford-White manufactures two brands of water heater - Bradford-White and Jetglas - and uses a 9-digit letter/number code with two letters signifying the year and month of manufacturer. The letters I, O, Q, R, U, and V are skipped to produce 20-year cycles. These cycles began in 1964 with the letter A, therefore the letter A in the first position of a B-W serial number can represent the years 1964, 1984 or 2004. B-W's second letter corresponds to the month of the year as with the A.O. Smith example above.

I did not see the chart you included in the response. I (and perhaps the inspector) just used the information you provided in the BW section.

1964 plus 7 (for the letter G) = 1971 or 1991 or 2011.

But, thanks for the clarification.

[Ken Meyer]

Thanks for the updated chart. Since tankless water heaters are becoming more common, can you add Takagi and Rinnai?

Someone can correct me if I'm wrong, but this how I think it works:

Takagi: format 01020000 First 2 digits are the month, 3rd and 4th are the year.

Rinnai: format 00.05-000000 First 2 digits are the year, 3rd and 4th are the month

[hausdok]

No,

You're still not using the chart correctly or understanding the above paragraph correctly. It's not 64 plus 7 for the letter G it's plus 6 for the letter G.

1964, 1984, 2004=A

2005=B

2006=C

2007=D

2008=E

2009=F

2010=G

2011=H

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

I've never used this full chart. Most water heaters are quite obvious in determining the date of manufacture. Bradford-White is the only one I refer to a chart to decode. Some time ago Mike O' put this together:

https://www.inspectorsjournal.com/forum ... rCodes.pdf

I mostly see B-W water heaters and this little B-W specific chart has been 100% accurate. You can usually confirm it with the date stamped on or in the lever on the relief valve. I can assure you G=2010 (unless it's 1970 or 1990).

[Bain]

I've never used this full chart. Most water heaters are quite obvious in determining the date of manufacture. Bradford-White is the only one I refer to a chart to decode. Some time ago Mike O' put this together:

https://www.inspectorsjournal.com/forum ... rCodes.pdf

I mostly see B-W water heaters and this little B-W specific chart has been 100% accurate. You can usually confirm it with the date stamped on or in the lever on the relief valve. I can assure you G=2010 (unless it's 1970 or 1990).

Same here. I use a Word .doc that I cribbed from here. It was written by some dude named James Katen.

I hope that if I were looking at a shiny, one-year-old heater and thought it was two decades old, some Spidey sense would start to tingle and tell me to take a closer look.

[Chad Fabry]

I'm working on a chart for Takagi and Bosch. It's a tankless job