6.2 Backflow Devices & Assemblies: Table 382.41-1, Limits & Installation

Reading Table 382.41-1

The table has eight condition columns: backpressure or back-siphonage, each split into low or high hazard, each split into continuous or noncontinuous pressure. A device is acceptable only where the table marks an X. Footnote a limits a mark to campgrounds and marinas; footnote b limits it to a maximum of 10 feet of backpressure. The table was recreated by CR 26-019, effective September 1, 2026.

"All" means every pressure condition in that hazard group.

Two quick rules: (1) for high hazard backpressure, only an air gap, RP or RPDA works; (2) for high hazard back-siphonage, add PVB, SVB, AVB (noncontinuous), barometric loop and vacuum breaker tee to that list.

Device limitations (SPS 382.41 (4))

Installation rules (SPS 382.41 (5))

• Install per the manufacturer and the code. Devices must be accessible for inspection, testing, maintenance and replacement, and protected from freezing.
• No device may be in an uninhabitable space subject to flooding, unless it has no vent port. A device with vent ports may never be in a pit, vault or depression below grade or floor, even one with a floor drain.
• Vent ports must face down or be shielded from debris, stay away from toxic fumes, drain dry, and discharge through an air gap.
• Inside a building, a PVB, RP or RPDA needs a drain or receptor for its vent-port discharge, with an air gap, and the discharge path may not create a nuisance. Local waste piping from a device must have a visible outlet, not inside a concealed space.

Clearances for testable assemblies (RP, RPDA, DC, DCDA, PVB, SVB):

Barometric loop: rises at least 35 feet above the highest downstream backpressure point and the discharge point, with no potable outlets downstream of the peak. Vacuum breaker tee (for water treatment device drains): the bottom of the horizontal portion is at least 1 inch above the receptor rim, and the tee and its vent are at least the drain's inside diameter. Chemical dispensers need an individually connected fixture supply or a pressure-bleeding device that creates a visible free flow into the drain.

Worked selections

1. Boiler with an automatic chemical feeder (high hazard, continuous, backpressure): an RP assembly or an air gap. A double check is not allowed.
2. Lawn sprinkler zone with a fertilizer injector, fed from a valve that stays open (high hazard, continuous pressure, back-siphonage only because there is no pump or elevated outlet): a PVB at least 12 inches above the highest head and the injection port, or an RP.
3. A low hazard process connection under continuous pressure with possible backpressure (the manufacturer specifies only nontoxic solutions): a double check assembly, dual check (ASSE 1024) or intermediate atmospheric vent device (ASSE 1012) satisfies the table, as would an RP or air gap. Footnote c reminds you to check SPS 384 for application-specific devices before choosing.
4. Mop sink faucet in a public building (high hazard, noncontinuous after the faucet, back-siphonage): an AVB on the faucet at least 6 inches above the sink rim, with no valve downstream, or a hose connection vacuum breaker.