How old is my Ruud water heater?

By Dana Whitlock. Updated October 2026. Official format.

Find the first run of four digits in your Ruud serial. The last two of those four are always the year of manufacture. On an older tank the two in front are the month; on a tank labeled in 2012 or later they are the week of the year, and a single factory letter comes first.

Ruud is a Rheem brand, and Rheem publishes how these serials work in a service bulletin titled for both Rheem and Ruud. That makes this an Official format on our site. If your label has a printed manufacture date, which Ruud labels from 2012 on do, use it and treat the serial as a cross-check.

Where to find the label on a Ruud water heater

A Ruud tank carries its rating label on the front of the jacket. If the installer left that side facing the room, you can read it standing in front of the heater. Bring a flashlight for a basement or attic install. The serial line sits near the model line. Nothing has to come apart to read it, and covers over the burner or heating elements should stay closed.

How to read the code

Older Ruud serials follow a month, year, plant letter, count pattern. In 0912D01234, the opening 09 means September, 12 means 2012, D is the production line and 01234 is the unit count. Newer Ruud serials put the plant first. A serial shaped like A141511869 reads as plant A (Montgomery), week 14, year 2015. The full set of plant letters on the newer label is A, W, Q, M and C, standing for Montgomery, Water Heater Innovations, Nuevo Laredo, Mexicali and Canada. Some older Ruud serials open with extra letters such as RU; disregard them and start at the first digit.

Real serials in this code

When the format changed

The serial 0912D01234 is a good illustration of why 2012 trips people up. It is a September 2012 build that still uses the old month-first layout, because not every Rheem-family factory moved to the plant-week-year label at once. Mexicali changed in April 2012 and Nuevo Laredo in June 2012, while other lines followed later. So for a 2012 or 2013 Ruud, check where the letter falls: after the four digits means month-year, before them means week-year. The year digits do not move between layouts, which keeps the age answer stable either way.

Who makes Ruud

Rheem Manufacturing owns the Ruud name, which honors Edwin Ruud, the inventor of the first automatic gas water heater. Ruud shares its serial code with Rheem and Richmond tanks. Warranty registration and lookup for Ruud run through Rheem's shared registration system, with a Ruud-branded page.

How sure is this?

Official format. Ruud publishes how its serial numbers encode the date. We tested the rheem rules against 17 serials, 13 of them with a date known from a recall notice, a printed label date or the maker. None decoded to a wrong year; codes whose year mark repeats show every possible reading. Always confirm with Ruud's serial lookup before you spend money on the answer.

Quick notes

• A two-digit value above 12 in the first pair of the date digits is a week, so the tank is from 2012 or later.
• A trailing letter after the five-digit count marks a conversion kit or variant. Leave it out of the date.
• Ruud's warranty page needs the serial; looking it up confirms both age and coverage left.
• For a tank older than DOE's average of about 14.5 years (gas) or 15.1 years (electric), get a replacement quote before authorizing a large repair.