Final answer:
The product ID markings on a tank, known as PIC codes, help identify the type of plastic the tank is made of, aiding in recycling and sorting processes.
Step-by-step explanation:
The product ID markings on a tank refer to the codes used to identify the type of plastic the tank is made of. These markings are known as Plastic Identification Codes (PIC). The PIC system was developed by the Society of the Plastics Industry to help with recycling and sorting of plastics.
Manufacturers of plastic products are required to use PIC labels in some countries, while in other regions it is voluntary. Consumers can find these labels on the base or side of plastic tanks, including food and chemical packaging containers.
The PIC codes are usually represented as a number within a recycling symbol. For example, the code '1' indicates that the tank is made of PET (polyethylene terephthalate) plastic, commonly used for water bottles.