Transport Tanks are manufactured with a specific gravity (SG) rating of 1, 1.5 or 1.7, depending on the weight of the material that needs to be transported. Water tanks, with a SG rating of 1, are produced in black or olive green. Chemical transport tanks, with an SG rating of 1.5 or 1.7, are produced in yellow, natural or beige. Horisontal transport tanks with a SG rating of 1.5 or higher may be used as underground storage tanks. Underground tanks should only be installed by qualified builders or plumbers in order to meet the criteria of your guarantee.