When to use: Every cross-connection between potable water and a source of contamination must be protected. The correct assembly depends on three factors: the degree of hazard (high = toxic contaminant, low = non-toxic pollutant), the backflow mechanism (backsiphonage vs. backpressure), and whether the device is under continuous pressure. Pick an application preset or set conditions manually.
High-hazard backsiphonage under continuous pressure calls for a Pressure (or Spill-Resistant) Vacuum Breaker. An RPZ also works if backpressure could later develop.
An air-inlet (vacuum breaker) plus a single check valve protects against BACKSIPHONAGE only — including HIGH-hazard backsiphonage. Rated for continuous pressure, but it CANNOT be used where backpressure can occur.
Field-tested at installation and annually — verify the air inlet opens and the check valve holds (ASSE 1020).
Install at least 12 in above the highest downstream outlet/head. The air inlet spits water when it opens — do not install indoors over finished space without drainage. Common on irrigation systems.