HTP® Water Heater and Boiler age

How to determine the date of production/manufacture or age of HTP^® brand Water Heater and Boiler Systems.

Water heaters in general have an average estimated useful service life of 10-12 years, though water quality, routine upkeep/maintenance, and location of the water heater will all play critical roles in the longevity of these systems.

The average service design life of boilers can vary from as little as 10 years to as many as 50 years depending on the type and quality of materials used in their manufacture. Routine upkeep/maintenance, regional weather/climate, and location/placement of the mechanical systems will all play critical roles in the longevity of these systems.

Parent Company: Ariston Thermo USA LLC

Subsidiaries or related brands: American Standard Water Heaters

The date of production/manufacture or age of HTP® brand Water Heater equipment can be determined from the serial number located on the rating data plate.

Example serial number styles/formats found:

→Style 1: I21M28666 (1994-2011)

→Style 2: 112116E205445 -or 2103302238194208 (2011-2022)

→Style 3: 3253087U4221610000082 (2021 - current)

Legend: Year is RED; Month is GREEN; Day or Week is BLUE

→Style 1: I21M28666

Ignore preceding digits in parenthesis: (21) in example image below

Year of manufacture can be determined by using the 4^th character (2^nd letter) of the serial number

Month of manufacturer can be determined by using the 1^st character (1^st letter) of the serial number

Day (of month) of manufacture can be determined by using the 2^nd and 3^rd digits of the serial number

Note: This format used from 1994 through 2011 only

→Style 2: **112116E205445 -or Style 2a: 2103302238194208**

Ignore preceding 2-digits if 16 digits or in parenthesis

Year of manufacture can be determined by using the 5^th and 6^th digits of the serial number

Month of manufacturer can be determined by using the 1^st and 2^nd digits of the serial number

Day (of month) of manufacture can be determined by using the 3^rd and 4^th digits of the serial number

Note: This format used from 2011 through 2022

→Style 3: 3253087U4221610000082

This style is always 21 characters in length. The date codes precedes the last 7 digits that usually begin with several leading zeros (denotes unique product number made on a single day of production).

Year of manufacture can be determined by using the 10^th and 11^th digits of the serial number

Calendar day of the year can be determined by using the 12^th thru 14^th digits of the serial number

Note: This style used since September 2021

HTP^® History¹

1974 - Company founded
1981 - Company incorporated
1984 - Began producing indirect water heaters for the space heating market and introduced one of North America’s first condensing water heaters for commercial and large residential applications.
1989 - First company in North America to offer a greater than 90 percent efficient, condensing, low mass boiler for the space heating industry.
2017 - Ariston Thermo acquired a majority stake in HTP Inc. effective July 31, 2017.

_{¹Excerpts from various industry resources.}

Every effort is undertaken to offer you correct and concise information to assist you in determining the age or manufacture date of water heating equipment. Users relying on this information do so at their own risk.

Page last updated: 02/11/2025

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