Every water heater carries a metal nameplate — the rating plate — with its model number, serial number, capacity, and manufacture date. You will need this information for warranty claims, ordering parts, and getting accurate replacement quotes. The good news: it takes about sixty seconds to find and read, once you know where to look.
Where the rating plate is
On nearly all tank water heaters, the rating plate is a sticker or metal tag on the side of the tank, usually toward the upper third and near the front for readability. It may be partially hidden behind insulation or a jacket panel — look for a rectangular label with dense small print. On tankless units, the plate is typically on the side or bottom of the cabinet, sometimes inside the front cover. If the label is painted over or corroded beyond reading, check any paperwork from the installation, or look for a second duplicate label the installer may have left near the unit.
Model number vs. serial number
These are different and serve different purposes. The model number identifies the product line — capacity, fuel type, and feature set. When you call for a part or a replacement quote, the model number tells the technician exactly which unit family you have. The serial number is unique to your individual tank; manufacturers use it for warranty verification and to trace production batches. When a technician asks "what's the model and serial," have both ready — a photo of the whole plate is even better, since it captures everything at once.
Reading the manufacture date code
Some plates print the manufacture date plainly. Many encode it in the serial number instead — and every manufacturer does it differently. Common patterns include the first two digits representing the year and the next two the week or month, or a letter-based month code followed by the year. Rather than guessing, search the manufacturer's name plus "serial number date code" — they publish decoder guides. Why does the date matter? Because water heater warranties run from the manufacture date (or install date with proof), and the unit's age is the single biggest input to any repair-vs-replace decision.
What the other fields tell you
- Capacity — the tank size in gallons (or flow rate in GPM for tankless). Essential for sizing a replacement correctly.
- Fuel type and input — gas units list BTU input; electric units list wattage and voltage. Never replace with a mismatched fuel or electrical spec without professional guidance.
- Maximum working pressure — the tank's rated pressure limit, relevant when diagnosing pressure issues.
- Energy factor / efficiency ratings — useful when comparing a repair against a modern replacement's operating savings.
- Certifications — listings like ANSI or UL marks confirm the unit met safety standards when built.
If the plate is missing or unreadable
It happens: labels get painted over, corrode away, or peel off in hot garages. Start with your installation paperwork or the contractor's invoice, which usually lists the model. Check for a second duplicate label — installers sometimes stick one inside the access panel or on nearby framing. As a last resort, a technician can usually identify the unit from physical characteristics: overall dimensions, burner or element configuration, valve types, and the gas control model narrow it to a short list. Once identified, photograph or write down the details immediately so you are not solving the same puzzle twice.
Why you'll need this info
Four situations demand the plate data: warranty claims (manufacturers verify age and model from the serial), parts ordering (elements, thermostats, gas valves, and anodes are model-specific), replacement quotes (accurate quotes need capacity, fuel, and dimensions — all derivable from the model), and recall checks (manufacturers occasionally recall specific serial ranges). Pro tip: photograph the rating plate today and save it with your home records. When the heater fails at an inconvenient hour, you will have everything a technician needs without crawling behind the tank with a flashlight. If you are in Apache Junction and need help decoding what you have, call (833) 713-2101 — a plate photo texted or described over the phone is enough for us to identify most units.
Related Questions
What if the rating plate is unreadable?
Try the installation paperwork first. Failing that, a technician can usually identify the unit from its physical characteristics — dimensions, burner or element configuration, and valve types narrow it down quickly.
Does the warranty start from the manufacture date or install date?
Typically the manufacture date, unless you can prove an install date with a receipt — in which case most manufacturers honor the install date. Keep your installation invoice.
Why does the technician need my model number before visiting?
So the right parts come on the truck the first time. Anodes, elements, thermostats, and gas valves vary by model — arriving with the correct part turns a two-visit job into a one-visit job.