Be also aware that mineral water can contain a high amount of sodium, which combined with the extremely high salt content of the average HK food (including imported stuff) can be very damaging to the circulatory system, nervous system, kidneys and liver. I believe, but need to confirm, that some imported stuff is worse than the local stuff. Better to have de-mineralised water, some spring waters (depending on the rocks through which it is filtered) or rain water by preference. If they have it on the bottle, check the contents for cations Na+ (sodium), Ca+ (calcium), K+ (potassium), Cu+ (copper). All of these have an effect on the nervous system if taken to excess. Also, fluoride must be used in moderation - it can have lethal consequences if taken to excess as well - particularly for babies and young 'uns. Tex, your metal filings could be a number of things and are unlikely to be absorbed through the human gut unless oxidised (rusted) and even then will be less than what you might get breathing in the air these days. So I would be more worried about soluble stuff that you can't see, not particulate stuff that you can. Personally, I find the taste of HK tap water difficult to take, but will perservere because it is likely to be less adulterated than bottled stuff, with all their added extras.