Hi, do you have any idea on those water filter from Amway? A friend of mine claim that it is better than the market. previously I bought one from best denki by mitsubishi. Ends up got to engage plumber myself and also change the tap. Considering the cost, luckily can return for a voucher to buy something else. By the way, do you know what's the brownish substance that line up within the walls of the hotpot. Is it rust?