What a dual check valve is protecting against
Backflow is water moving the wrong way through a pipe — back into the drinking water main instead of forward to the fixture. It happens when downstream pressure drops below supply pressure, and it's a genuine contamination risk if whatever's downstream (a chemical dosing unit, an irrigation system, a washing machine, a hose connected to a trough) could pull contaminated water back with it. A dual check valve, like Bluegum's Dual Check Valve (BLUEGUM-DCV-C, $14.99), uses two independent check mechanisms in series so that if one fails, the second still blocks reverse flow.
Reading the rating
This valve is rated 150–500kPa and WaterMark approved, with a Neoperl valve core and a 15mm male x female chrome fitting. WaterMark approval matters because it confirms the valve has been independently tested against the Australian plumbing product standard — not every backflow device sold online carries it, and using an uncertified device on a potable line can fall foul of local plumbing code.
Where dual check valves are typically required
Common fit points include appliance connections (washing machines, dishwashers), garden tap and irrigation take-offs, and any fixture where there's a chemical or non-potable risk downstream. Many water authorities specify a minimum level of backflow protection at these points as a matter of course, separate from whatever protection exists at the water meter.
Dual check vs a single check valve
A single check valve relies on one moving part to block reverse flow — if it wears or jams open, there's no backup. The dual check design is the more robust option for the same reason a seatbelt and an airbag both matter: redundancy where failure has real consequences. For temperature-related protection on hot water lines, see our tempering valve guide.
Frequently Asked Questions
What's the difference between a dual check valve and a single check valve?
A dual check valve has two check mechanisms in series, so if one fails the other still prevents backflow — a single check valve has only one line of defence.
Is WaterMark approval mandatory for backflow devices?
Plumbing regulations in Australia generally require WaterMark-certified products for work on regulated plumbing, including backflow prevention devices — check your local water authority's requirements for the specific application.
Where should a dual check valve be fitted?
Typically at the point where a non-potable or chemical risk could occur — appliance connections, garden tap take-offs and irrigation lines are common locations.
What does the 150–500kPa rating mean?
It's the supply pressure range the valve is designed to operate correctly within — check your system's static pressure falls inside that range before fitting it.