I’m old enough to remember when milk was marketed in three-quart high density polyethylene refillable plastic bottles (replacing the heavy refillable glass bottles). As I recall, the main reason they stopped being refilled is that people would occasionally store chemicals in them (solvents, gas, etc.) which were impossible to clean from the plastic. I assume that the combination of new sniffing/detection technology and cleanable characteristic of PET plastic will address any possible contamination issues with the 500 ml water bottles. I applaud Canadian Springs for their bold move and will be interested to see how their refillable deposit-return containers will compete in non-deposit jurisdictions. It strikes me as quite a gamble (unless of course the program is only for deposit provinces).