How old is my Lochinvar water heater?

Serial number age decoder for Lochinvar tank water heaters: 8 format eras, the decode rule in plain English, transcribed tables, and the official lookup.

• Lochinvar water heater serial numbers in the 1979 to 2011 format encode the year as letter 1, Bradford White 20-year cycle (K=1993, A=2004 ... J=2012) and the month as letter 2 (A=Jan..M=Dec, I skipped) (source: building-center.org).
• Example: serial KJ-1000130 decodes to September 1993.
• Lochinvar water heater serial numbers in the 2011 to present format encode the year as digits 1-2 (20YY) and the week as digits 3-4 (source: building-center.org).
• Example: serial 1142N012345 decodes to week 42 of 2011.
• Lochinvar water heater serial numbers in the 1978 to present format encode the year as digits 1-2 after the letter (YY) and the month as letter 1 (A=Jan..M=Dec, I skipped) (source: building-center.org).
• Example: serial J-930001 decodes to September 1993.

Format eras

• 2011 to present VERIFIED
  ####A######digits 1-2 (20YY)
• 1984 to present VERIFIED
  ########digits 1-2 (YY)
• 1979 to 2011 VERIFIED
  AA-#######letter 1, Bradford White 20-year cycle (K=1993, A=2004 ... J=2012)
• 1978 to present VERIFIED
  A-######digits 1-2 after the letter (YY)
• 1978 to present VERIFIED
  A##A########digits 2-3 (YY)
• 1974 to 1997 VERIFIED
  A##-####Adigits 2-3 (19YY, table 82-97)
• 1968 to 1981 VERIFIED
  #A###letter(s) after the leading number: P=1970 R=1971 S=1972 T=1973 U=1974 V=1975 W=1976 X=197
• 1965 to 1986 VERIFIED
  A#####digits 2-3 (19YY)

How to read the serial

2011 to present formatVERIFIED

Shape ####A###### · example 1142N012345 · confidence high

Year

digits 1-2 (20YY)

Week or month

week = digits 3-4

Plant

letter 5

Example: serial 1142N012345 decodes to week 42 of 2011.

1984 to present formatVERIFIED

Shape ######## · example 85041234 · confidence medium

Year

digits 1-2 (YY)

Week or month

month = digits 3-4

Example: serial 85041234 decodes to April 1985.

1979 to 2011 formatVERIFIED

Shape AA-####### · example KJ-1000130 · confidence high

Year

letter 1, Bradford White 20-year cycle (K=1993, A=2004 ... J=2012)

Week or month

month = letter 2 (A=Jan..M=Dec, I skipped)

Example: serial KJ-1000130 decodes to September 1993.

1978 to present formatVERIFIED

Shape A-###### · example J-930001 · confidence medium

Year

digits 1-2 after the letter (YY)

Week or month

month = letter 1 (A=Jan..M=Dec, I skipped)

Example: serial J-930001 decodes to September 1993.

1978 to present formatVERIFIED

Shape A##A######## · example A07H00123456 · confidence medium

Year

digits 2-3 (YY)

Week or month

month = letter 1

Example: serial A07H00123456 decodes to January 2007.

1974 to 1997 formatVERIFIED

Shape A##-####A · example J93-1030F · confidence medium

Year

digits 2-3 (19YY, table 82-97)

Week or month

month = letter 1

1968 to 1981 formatVERIFIED

Shape #A### · example 5Y013 / 6S1064 / 11AA0365 · confidence medium

Year

letter(s) after the leading number: P=1970 R=1971 S=1972 T=1973 U=1974 V=1975 W=1976 X=1977 Y=1978 Z=1979 AA=1980 BB=1981

Week or month

month = leading 1-2 digit number (1=Jan..12=Dec)

Example: serial 5Y013 decodes to May 1978.

1965 to 1986 formatVERIFIED

Shape A##### · example M78013 · confidence medium

Year

digits 2-3 (19YY)

Week or month

month = letter 1

Example: serial M78013 decodes to December 1978.

Where the data plate is on a water heater

The rating plate is a large label on the side of the tank near the top or beside the control. The serial is printed on it, often beside the model number and the ANSI standard line.

General guidance, not brand-specific: the owner's manual or the installer can point to the exact spot. See the data plate guide.

For scale only: the InterNACHI Standard Estimated Life Expectancy Chart for Homes lists Water Heater (conventional) at 6 to 12 years of expected service (nachi.org). That chart is a guideline, not a prediction for your unit.

What we could not confirm

• The 1974 to 1997 format is documented but not decodable here: letter-year rule without a transcribed table.
• No official online lookup URL was verified for Lochinvar.
• 9 styles, several outsourced (style 1 = Bradford White letter scheme; style 2 = AO Smith YYWW). Charts on building-center were copied from lochinvar.com/_linefiles/WARR-15.pdf (now 404). No online age/warranty lookup found (lochinvar.com/warranty 404).

Sources

• https://www.building-center.org/lochinvar-hvac-age/
• img: Lochinvar-Style-1_Serial-Number.png (from Lochinvar WARR-15.pdf)
• img: Lochinvar-Style-3_Serial-Number_slide-1.png
• img: Lochinvar-Style-5_Serial-Number.png
• img: Lochinvar-Style-7_Serial-Number.png

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