Did you guess that it's just for recycling?
Then you are WRONG!!!!!!
THE NUMBER TELLS YOU THE CHEMICAL MAKE UP OF THE PLASTIC.....
1) Polyethylene terephalate (PET)
2) High density polyethylene (HDPE)
3) Unplasticised polyvinyl chloride (UPVC) or Plasticised polyvinyl chloride (PPVC)
4) Low density polyethylene LDPE
5) Polypropylene (PP)
6) Polystyrene (PS) or Expandable polystyrene (EPS)
7) Other, including nylon and acrylic What you aren't told is that many of the plastics used are toxic and the chemicals used to create a plastic can leach out of the plastic and into the food / drink. Think about it, how many times have you or a friend said "I don't like this, it taste like the plastic bottle ..... "
THAT'S BECAUSE YOU ARE TASTING THE PLASTIC
The WORST ONES are Nos: 3, 6, and 7 !!!
DO NOT USE THESE NUMBERS if stated at the bottom of the bottle) !!!
Check out this chart that breaks down the plastic, its uses and chemical makeup (I find #7 a little scary) http://www.epd.gov.hk/epd/english/environmentinhk/waste/guide_ref/guide_plascod3.html
AVOID re-using plastic bottles RIGHT AWAY !!!