The type of stainless steel pipe used in chilled water systems originates from the largest “family” of stainless steel, which is called austenitic or 300 series stainless steel pipe. Included in the 300 series are the most common applications for chilled water, types 304/304L and types 316/316L made to the specifications of ASTM A312. The “L” designation means that the stainless steel contains less than 0.03% carbon. This is beneficial if the pipe needs to be welded.
Types 304/304L are used more for general corrosion applications and types 316/316L have a higher corrosion resistance to chlorides and may be desired for chilled water systems based upon the chemical composition of the water supply. Stainless steel pipe is generally available in diameters up to 36 inches with dimensions ranging from Schedule 5S to 160S with Schedule 10S being the most common for chilled water systems. Schedule designations indicate the pressure capacity of the pipe. When specifying the Schedule of stainless steel pipe, an “S” is added after the Schedule number to differentiate stainless steel from other steel pipe.