Find the manufacture year of any Weil-McLain boiler from the serial number.
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How to decode the serial number
Weil-McLain is one of the oldest and most respected boiler brands in North America. Their serial numbers encode the manufacture date in a straightforward format.
1990 to Present
First two digits = year, next two = week.
1723A123456
Position
Meaning
Example
1–2
Year — 2017
17
3–4
Week — Week 23
23
5+
Sequence — Ignore
A123456
Where to find the serial number
The data plate on a Weil-McLain boiler is typically on the front or side of the unit.
For gas boilers, look near the gas valve or on the jacket door.
The serial number begins with two year digits followed by two week digits.
Decoded examples
2317A123456
→ Week 17, 2023
23 = 2023, 17 = week 17
9832B987654
→ Week 32, 1998
98 = 1998, 32 = week 32
Life expectancy
Expected lifespan: 25–30 years for cast iron Weil-McLain boilers. They are among the most durable heating appliances available. High-efficiency condensing models typically last 20–25 years.
Common questions
Cast iron Weil-McLain boilers (like the Gold series) are legendary for longevity — 25–35 years is common with proper maintenance. High-efficiency condensing boilers (Ultra series) typically last 20–25 years. Some vintage cast iron Weil-McLain boilers from the 1960s and 70s are still in service.
Replace when it requires frequent repairs, efficiency has dropped noticeably, or it is over 25 years old. A high-efficiency replacement (90%+ AFUE) can significantly reduce fuel bills even if the old boiler is still functional.
The first two digits are the 2-digit year and the next two digits are the week of manufacture. A serial starting with 1734 was made in week 34 of 2017.