46 CFR § 76.33-15 - Piping.
(a) Individual pipes must be not less than 3/4-inch standard pipe size.
(c) Where a smoke detection system serves a space used alternately for liquid and dry cargo, a valve must be installed between the tank and the detection cabinet so that the line may be shut off when liquids are carried. When the smoke detection system is combined with a fire extinguishing system, the operation of the valve must not affect the operation of the fire extinguishing system.
(d) All piping, valves, and fittings must be securely supported, and where necessary, protected against injury. The piping must be installed with as easy bends as practicable, and must be installed to grade to low points for drainage.
(e) Drains and dirt traps must be fitted where necessary to prevent the accumulation of dirt or moisture.