The backflow preventer prevents contaminated water from back-shiphoning into the the potable water supply system. This may occur when the pressure in the potable water supply system changes causing water flow reversal. The backflow preventer is installed between the potable water supply system and the internal domestic water supply system, creating a safety zone which prevents the water in the two systems from coming into contact.
Dual check continuous pressure backflow preventer with atmospheric vent|250 deg F emergency backpressure temperature
Caleffi Backflow Preventer, Continuous, Series: 573, 1/2 in Nominal, FNPT, 175 psi, 32 to 210 deg F, Dual Check Backflow, Media: Water, Brass Body, 4-1/2 in W