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
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
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.
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