OBS,
You are coming on vacation - you are reading direct, first hand trip reports from people who are here and have been here and there is no mention of any water pollution. None! ZERO! There is limited water pressure at times - since you have been here 5 times before you have experienced the low water pressure before. You will not notice anything different than you have in the past.
I hate to be so blunt, but you really do need to take a chill pill - being overly paranoid is no way to go through life man....
Your vacation will be fine and enjoyable if you simply let it - please allow yourself to enjoy it.