Lochinvar water heater age by serial number

Reviewed 2026-10-151 primary sourceSee sources

Lochinvar, part of A. O. Smith, publishes its serial layouts in a warranty reference. Tank water heaters used a two-letter year-and-month code until 2011, then an 11-character code that starts with the year and week.

Covers: Lochinvar tank-type water heaters (residential and commercial tanks, Hi-Power and jacketed tanks). Lochinvar boilers and some other series use different layouts.

Where to find the serial number

• On commercial gas tanks the data plate is about halfway down the front of the jacket; on residential tanks it is about half to two-thirds of the way down the front or right side.^[1]

Date formats Lochinvar documents

Year letter + month letter1993–2012 letters

Lochinvar used this layout from 1979, but its table lists only the letters for 1993 to 2012, so older letters aren’t decoded.^[1]

Year + week + plant (11 characters)2011 on

Lochinvar’s reference lists years 2011 to 2021 for this layout.^[1]

What Lochinvar says

• Lochinvar’s residential tank warranty runs from 60 days after the manufacture date shown by the serial number, per this reference.^[1]

Worked examples

• KJ-1000130: K is 1993 and J is September: built September 1993 (Lochinvar’s example).^[1]
• 1142N012345: Week 42 of 2011, plant N (Lochinvar’s example).^[1]

What the serial can’t tell you

• Lochinvar marks all of its charts as reference only and gives its parts and service department as the contact for questions.^[1]
• The serial gives a month or week of manufacture, not the installation date.^[1]
• Year letters before 1993 and the reuse of letters after 2012.
• The 13-character layout used by some Lochinvar boilers and commercial series isn’t covered here.