This standard applies only to those devices classified as backflow preventers that are designed for installation on laboratory faucets on the discharge side of the last shut-off valve. These devices are not for use under constant pressure conditions. These devices consist of two independently acting check valves, force loaded or biased to a normally closed position, and between the check valves a means for automatically venting to atmosphere, force loaded or biased to normally open position.
The devices shall be designed for a minimum working pressure of not less than 125.0 psi (861.9 kPa).
The devices shall be designed for flow temperatures between 33.0 °F to 180.0 °F (0.6 °C to 82.2 °C).
Minimum Flow Capacity
The device shall have a minimum flow capacity of 4.0 GPM (15.0 L/min) with a maximum pressure loss through the device of 20.0 psi (137.9 kPa).
Connections shall be suitable for laboratory faucets. (Inlet and/or outlet connections are permitted to be different when required for special installations.)
Flow Way Open Area
The least total cross-sectional area of the air flow ways, including the seat area of the air vent valve, shall be not less than the least total cross-sectional area of the waterflow passage or passages upstream from the air vent valve. The minimum cross-sectional dimensions of any air port or flow way, not including the valve lift, shall not be less than 3/32" (2.4 mm). These requirements shall be verified by the testing agency.
a. The atmospheric vent shall be constructed so that it will open when the supply pressure is atmospheric or below.
b. The atmospheric vent shall be constructed so that under a back pressure condition it will open.
c. The atmospheric vent shall be constructed to provide vacuum breaking ability.
a. The internal parts of the device shall be accessible for inspection, repairs or replacements.
b. All replaceable parts of the device of the same size and model shall be interchangeable with the original parts.