IMO,if there is no any info on the dwg legend section , there must be a job specific separate sheet for line numbering system.
Pls look to the SAES L 132 (Material Selection for Piping Systems )
The diameter 2'' and service FW ,in case of sea water and aboveground piping,the piping material 90-10 Cu-Ni or 254 SMO S/S depending on the fluid velocity.
..And the relevant piping class 1SY0W as per SAES L 105
Will you pls post the relevant dwg to get better responds?