As far as I know, there's no real water market anywhere, it's all granted by governments. Unsurprisingly, some governments are better than others at managing such resources, and large companies take advantage of that.

My point is not that markets in water and hearing aids can't fail, it's that "the demand curve is almost completely inelastic" isn't an explanation. Water and sewage are generally provided by public utilities (in non-rural areas, at least), but the conventional justifications involve the "natural monopoly" of the associated infrastructure, not the shape of the demand curve. People in developed countries would pay almost anything to have flushing toilets, but septic systems (to which infrastructure arguments don't apply) are usually provided by private companies.