The short answer
The serial number on a Rheem water heater’s rating plate tells you when it was made. If you’re in Northern Virginia deciding between a repair and a new tank, that date is the first thing to know. Since 2012 the serial starts with a letter, then two digits for the week and two for the year. M141209135 was made in week 14 of 2012. Older serials start with four digits for the month and the year.
Where the label is
On a tank, the rating plate is on the front, near the gas control or the upper panel. On a tankless, it’s on the front or the right side. Snap a photo of it while you’re there: the model number is on the same plate, and we’ll ask for both.
$99 Water Heater Flush
We drain and flush the tank, check the anode rod and test the relief valve, then go through the house's plumbing with photos, included. See the flush
Want your own number before anyone comes out? The water heater estimator prices your house in a few questions.
Since 2012: letter, week, year
Rheem switched formats between April and June of 2012. The new serial reads like this:
Swipe to see all columns →
Swipe to see all columns →
| Part | Example: M141209135 | What it tells you |
|---|---|---|
| First letter | M | The plant that built it |
| Next two digits | 14 | The week of the year |
| Next two digits | 12 | The year: 2012 |
| The rest | 09135 | The unit’s number |
Swipe to see all columns →
Swipe to see all columns →
| Letter | Plant |
|---|---|
| A | Montgomery, Alabama |
| M | Mexicali, Mexico |
| Q | Nuevo Laredo, Mexico |
| W | Water Heater Innovations |
| C | Canada |
A letter after the number, like A, B or C, marks a converted unit. It doesn’t change the date.
Before 2012: month, year, letter
The older serials are ten characters: two digits for the month, two for the year, a letter for the plant, then the unit’s number. Rheem’s example is 1209D01234: made in December 2009. Month first, then the year. If the first pair is higher than 12, it isn’t the month, so send us the photo and we’ll read it.
Our water heater age page decodes the other brands too.
Why the age matters
Rheem figures its warranty from the date of manufacture, so the serial is what a warranty claim is checked against, not the day it went in. And age drives the repair call. Most tanks last 8 to 12 years, and a tankless kept descaled can go about 20. Our water heater lifespan guide has the detail.
- Under 8 years with a bad gas control, element or thermostat: fix it.
- 8 to 12 years: fix small things, and start planning.
- Past 12, or any age leaking from the tank itself: replace it. A tank leaking from the bottom can’t be repaired. Our leaking water heater guide shows what to look for.
What extends it
Two things: flushing the sediment out and replacing the anode rod before it’s gone. Our anode rod guide explains the rod. The water heater flush is $99 (normally $199): we drain and flush the tank, check the anode rod and test the relief valve.
When it’s time
If the serial says it’s past its years, the water heater estimator shows the installed price of a new tank, and $500 comes off it. If yours is showing a code instead, our Rheem blinking light guide, Rheem electric guide, Rheem hybrid codes and Rheem tankless codes cover them.
Related: Rheem water heater troubleshooting, what not to do to your water heater, no hot water and water heater service.
Every code meaning here comes from Rheem’s own documents: serial number bulletin TB 1207 and serial number page.
Call or book
A plumbing diagnosis visit is $49, or $250 after hours, and you get the price of the fix before we start. Call (703) 997-9757, day or night, and tell us the code, or book the water heater flush from goswiftpro.com/cookiesoffer by November 30 and a box of warm MOLTN cookies comes with it. Every current deal is on our offers page. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
How do I tell how old my Rheem water heater is?
Read the serial number on the rating plate. Since 2012 it starts with a letter, then the week and the year: M141209135 is week 14 of 2012. Older serials start with the month and the year.
Where is the serial number on a Rheem water heater?
On the rating plate on the front of a tank, near the gas control or upper panel. On a tankless, the front or right side.
How long does a Rheem water heater last?
Most tanks last 8 to 12 years. A tankless that gets descaled can go about 20.
Does the Rheem warranty start at install or manufacture?
Rheem’s serial number bulletin says the warranty is figured from the date of manufacture, which is why the serial matters.
