In all refrigerating systems, there shall be a relief valve
from the high-pressure side and a relief valve from the low-pressure
side, piped to the outside atmosphere so as to discharge not less
than 12 feet above the roof or surrounding roofs; the pipe area shall
be not less than the combined area of relief-valve outlets and to
have the orifice turned downward. When ammonia is used, the discharge
from relief valves may be piped into a tank of fresh water used for
no other purpose and prevented from freezing without the use of chemicals,
containing at least one gallon of water for each pound of ammonia
in the system.