Guide
How to Read a Backflow Preventer Tag (Brand, Size, Model) Before You Order
Before you order a repair kit or freeze bag, read three things off the backflow preventer tag: brand, size, and model. They’re almost always on the metal ID plate on the body or cover—and size is also stamped on the shutoff valves. Wrong model number = wrong kit. Wrong size = a bag that won’t cover.
Where to look
- Metal ID plate / tag — riveted or screwed on the body, side, or cover. Wipe dirt and oxidation.
- Cast or stamped marks in the brass if the plate is gone.
- Both shutoff valves — pipe size (¾", 1", 2"…) is usually stamped or cast here, which helps when the tag is unreadable.
Photograph the tag square-on in daylight. Add one full-assembly shot and one side shot if you want us to size a freeze bag.
What to write down
| Field | Why it matters |
|---|---|
| Brand | Watts, Wilkins/Zurn, Febco, Ames, Apollo, etc. Kits are brand-specific, so identify the backflow preventer brand first. |
| Size | Matches the kit SKU and narrows the freeze-bag size. |
| Model | The backflow preventer model number, e.g. 009M2, LF009M2, 009M3, 975XL2, 975XL3 — revision letters matter. |
| Serial (optional) | For test reports / utility records—not usually required to pick a rubber kit. |
Examples:
- Watts 1" LF009M2 → 1" Complete Rubber Rebuild path—not a 009M1 or 009M3 kit. Guide: Watts 009M2 rubber rebuild.
- Wilkins ¾" 975XL2 → XL/XL2 shared kits. 975XL3 → separate kits. Guide: 975XL vs XL2 vs XL3.
If the tag is missing or painted
- Size from the shutoffs.
- Clues: relief valve under the body (RP/RPZ), number of check covers, canopy style on a PVB.
- Send clear photos to sales@thebackflowdepot.com or use the Repair Parts Finder once you have brand + size + best-guess model.
Ordering paths after you read the tag
- Repair kits: Repair Parts Finder or Repair Parts collection.
- Freeze bags: measure or use app.thebackflowdepot.com for 3"+; story at Freeze bags; shop Freeze Bags collection. How-to: Measure for a freeze bag.
What the model line looks like by brand
Every manufacturer stamps the same three facts, but the format differs:
- Watts plates read like 009M2 or LF009M2. The LF prefix marks the lead-free version of the same model; the M2 is the revision, and it is the revision that decides the kit. Older 009 and 009M1 devices use different internals. On ¾" and smaller, some plates read 009M3 or LF009M3: that is a different model with its own parts (on ¾", the complete rubber kit is Watts 888526), so the 009M2 kit is the wrong box.
- Wilkins (Zurn) plates read 975XL, 975XL2 or 975XL3. XL and XL2 share kits; XL3 is a separate design with its own part numbers.
- Febco, Ames and Apollo follow the same pattern: a base model number plus a suffix or revision. Copy the whole string, suffix included.
If you are not sure which characters are the model and which are the serial, photograph the entire plate. We read them all day.
The three-line order checklist
Write this down before you open the shop or call:
- Brand — as printed on the plate, not the name on the box the last kit came in.
- Size — the nominal pipe size stamped on the shutoffs (¾", 1", 1½", 2" and so on).
- Model — the full model string, revision and prefix included.
With those three lines the Repair Parts Finder takes you straight to the kit, and the size tells you whether a standard freeze bag applies.
Mistakes we see at the counter
- Ordering from the old paperwork. The device may have been replaced since the last test report was filed. Read the plate on the device that is actually in the ground.
- Treating 009, 009M2 and 009M3 as the same thing. They are not, and the complete rubber kits do not interchange.
- Grabbing an XL2 kit for an XL3. The tag says XL3 for a reason.
- Guessing the size from the pipe. Reducers are common. The size on the shutoffs is the size of the assembly.
- A blurry photo of a dirty plate. Wipe it, shoot square-on in daylight, and send one shot of the whole assembly too.
Frequently asked questions
Do I need the serial number to order a kit?
No. Brand, size and model pick the kit. Water purveyors and testers want the serial number for test reports and records, so it is worth writing down, but it does not change which parts you buy.
My tag says LF in front of the model. Is that a different device?
It is the lead-free version of the same model. On the sizes we stock, the product page lists both the standard and LF versions where the kit fits both — check the “fits these devices” block before you order.
The plate is gone. Can you still identify it?
Usually. Send clear photos of the whole assembly, the shutoffs (for size) and any casting marks to sales@thebackflowdepot.com. The relief valve position, number of check covers and body shape narrow it down quickly.
Is the size on the tag the pipe size?
It is the nominal size of the assembly, which matches the pipe size stamped on the shutoffs. That is the size you use for both repair kits and freeze bags.
More guides
- How Much Does It Cost to Fix a 2 Inch Backflow Preventer?
- Freeze Bag vs Heated Enclosure for Backflow: When Each Wins in NorCalIn Northern California a fitted freeze bag is the usual answer for residential and light-commercial assemblies. A heated enclosure wins when the line cannot freeze or the spec names ASSE 1060 Class I.
- How to Measure a Backflow Preventer for a Freeze BagSize a freeze bag off the full installed assembly: length, width, height and pipe size. We match it to one of five standard sizes, going up one if you are between. Use the photo sizer for 3-inch and larger.
- Wilkins 975XL vs 975XL2 vs 975XL3: Which Kit You Need975XL and 975XL2 share the same repair kits for a given size. 975XL3 is a different design with its own kits. Read the tag, then use this size and model map with links to each kit.