Most pool pump, filter, heater, and controller serial numbers contain the manufacture date. Brands write it as a year plus a day of the year, a year plus a production week, or a year plus a month, and the format depends on the brand, the product, and the era. Find the serial number on the manufacturer's product tag, match its pattern to the brand, and confirm the result in the Grey Shark equipment lookup.
Why the Date Matters
The build date tells you how old the equipment is. That helps when you're deciding whether to repair or replace a pump or heater, when you're ordering parts for a specific production run, and when you're checking warranty coverage.
It isn't the install date. A unit can sit in a warehouse for months before it goes on a pad. Think of the manufacture date as the earliest the clock could have started, not the day your coverage began.
Three Ways a Serial Number Holds a Date
Every brand picks one of three styles. They differ in how exact the answer is.
Day of the year
Exact day
Three digits count the days from January 1, so 001 is January 1 and 365 is December 31. A two digit year sits next to them. This is the most precise format. Hayward and Pentair both use it on common product lines.
Year and week
Within a week
Two digits for the year and two for the production week, from 01 to 53. You get the week the unit was built, not the exact day. Newer Jandy and Fluidra serials work this way.
Year and month
Within a month
The month shows up as two digits, or as a single letter from A through M. Older Hayward, Sta-Rite, and Jandy serials often use this style.
How the Major Brands Do It
These are the common layouts. Product lines and eras vary, so treat them as a guide to what you're looking at, not a promise about every unit.
Hayward
Newer serials start with 21, then a two digit plant code, a two digit year, and a three digit day of the year. Older ones put a month where the day goes. Goldline controls use a different layout: one digit, one letter, the year, then a day or a month.
Illustration: 21 12 24 105 means plant 12, day 105 of 2024, which is April 14, 2024.
Pentair
Many Pentair serials carry a five digit block with the day of the year first and the year after it. Longer serials put a plant code ahead of that block and a sequence after it. Pentair heaters can lead with a full date instead. Older Sta-Rite equipment uses a month letter followed by the year.
Illustration: 21511 means day 215 of year 11, which is August 3, 2011.
Jandy and Fluidra
From roughly 2006 to 2014, Jandy serials began with four letters for the product line and plant, then year, month, and day, then an eight digit sequence. Newer Fluidra serials are 18 characters long and hold the production week and year in the back half. Older equipment can use a month letter instead.
Example: AT WN09 0102 15250097 decodes to January 2, 2009. AT-EC02-0514-0825-1506 decodes to week 8 of 2025, so late February 2025.
Century and A.O. Smith
Motors from Century and A.O. Smith usually carry optional letters, then a three digit day of the year and a two digit year.
Motors are often swapped on their own, so read the pump label for the pump's age.
Reading Yours in Four Steps
1. Find the right label
Use the manufacturer's product tag on the pump, filter, heater, or controller, not a motor or valve label. The serial number locations guide shows where each brand puts it.
2. Identify the brand and product type
A pump and a heater from the same brand can use different formats, and so can two eras of the same product line.
3. Match the pattern
Count the digits and look at what sits where. A five digit block that ends in two year digits points to a day of the year. Two pairs of digits that look like year then week point to a production week.
4. Check the result
A date that lands in the future, or before the product existed, means you matched the wrong format. Enter the manufacturer, model, and serial number in the lookup tool to confirm.
Where Date Codes Mislead
Similar shapes cause most of the mistakes. A five digit block can be a day and a year on one brand and a year and a week on another, and both decode to a believable date. Reading the wrong format gives you a wrong answer that looks right.
Motors, replacement parts, and rebuilt units cause the rest. The label you're reading has to belong to the product you're asking about. And some serial numbers don't carry a date at all.
That's why our equipment lookup applies brand-specific rules and returns no date when none of them fit. A blank is more useful than a guess. If you're weighing a repair against a replacement, our repairs and equipment team can read the label and tell you what you have.