Sub Zero Covers
Tan insulated backflow cover in a retail parking-lot island, fitted around the assembly with the yellow fire department connection riser left clear.
Retail center — FDC riser left clear of the cover

By assembly and size

1½" RP backflow cover

1½" RP backflow cover sizing starts with the assembly on the tag. At 1½", 9 RP assemblies from the brands we pattern for are common: Watts 009 / LF009, Watts 909 / LF909, Febco 825Y / LF825Y, Febco 860 / 860U / LF860, Zurn Wilkins 975XL2, Zurn Wilkins 375XL, Ames LF4000B / 4000B, Apollo / Conbraco RP4A / RPLF4A, and Apollo / Conbraco RP40. The price list maps this pipe size to 3 stock covers, and the published dimensions below say which one to pull.

Request distributor access Talk to sales

What "1½" RP" covers on a counter

Reduced pressure zone (RP / RPZ). At 1½" the assemblies your customers bring in are Watts 009 / LF009, Watts 909 / LF909, Febco 825Y / LF825Y, Febco 860 / 860U / LF860, Zurn Wilkins 975XL2, Zurn Wilkins 375XL, Ames LF4000B / 4000B, Apollo / Conbraco RP4A / RPLF4A, and Apollo / Conbraco RP40. They are not the same size: the Zurn Wilkins 375XL is 15.25" end to end and the Apollo / Conbraco RP40 is 19.5", so "a 1½" RP" is not a single envelope.

The stock covers for 1½"

The April 2026 price list maps 1½" to 30 × 24 (DS3024), 36 × 24 (DS3624), and 42 × 24 (DS4224). The table below orders them closest fit first for each assembly: the cover should clear the end-to-end length across both shutoff handles with room to close at the base.

Relief valve drainage

Every assembly on this page has a relief valve that discharges downward, and on the Febco 825Y from the side of the body. Leave that path open. Close the cover to the pad around the assembly, never under the relief port.

When to measure instead

Unions, strainers, OS&Y gates, and wall-tight mounts all move an assembly off its spec sheet. If the tag is gone or the install is odd, measure it or send photos for a custom cover. For the type as a whole see RP covers; for another size, start at the fitment hub.

Sub Zero Covers sells through distributors only. Distributor accounts see pricing and availability in the portal; everyone else orders through their supply house, or applies for distributor access.

Assemblies at this size

1½" reduced pressure zone assemblies and the cover that fits

Dimensions in inches from each manufacturer's spec sheet with standard shutoffs. Length end to end; heights from the pipe centerline. The cover column is the closest stock fit by published length; confirm against the assembly in front of you.

AssemblyLengthAbove CLBelow CLClosest stock cover
Watts 009 / LF00917.875"3.5"3.25"30 × 24 (DS3024)
Watts 909 / LF90919"5.5"7.625"30 × 24 (DS3024)
Febco 825Y / LF825Y17"4.875"5.25"30 × 24 (DS3024)
Febco 860 / 860U / LF86016.375"4.25"7.625"30 × 24 (DS3024)
Zurn Wilkins 975XL217.375"5"6.75"30 × 24 (DS3024)
Zurn Wilkins 375XL15.25"3.75"5.75"30 × 24 (DS3024)
Ames LF4000B / 4000B17.875"3.5"2.5"30 × 24 (DS3024)
Apollo / Conbraco RP4A / RPLF4A18"4.5"5.375"30 × 24 (DS3024)
Apollo / Conbraco RP4019.5"7.125"5.5"30 × 24 (DS3024)

Common questions

Which cover fits a 1½" RP?
One of 30 × 24 (DS3024), 36 × 24 (DS3624), and 42 × 24 (DS4224), chosen by the assembly's end-to-end length. The table above names the closest fit for each RP at this size.
Do all 1½" RP assemblies take the same cover?
Not always. At this size the published lengths run from 15.25" (Zurn Wilkins 375XL) to 19.5" (Apollo / Conbraco RP40). Order by model.
Is this a heated enclosure?
No. Sub Zero Covers are insulated, unheated covers (R-13 standard, R-30 extreme weather). They are not ASSE 1060 listed enclosures. Where a spec calls for a Class I heated enclosure, ask sales before quoting.

Related pages