Recycling etiquette

I've been wondering about whether we need to wash the bottles or the cartons before putting them into the recycling bin. I had a vague impression that we need to do that, but I feel that it's kind of a waste of water to do that. Today I found the answer to this question. So we should wash those containers before recycling to reduce contamination and improve recycling efficiency, but we can use washing-up water. This is in the spirit of reuse as well. In this way, we won't waste clean water and the recyclate does not need to be very clean anyways.