Sounds like it's a problem with the pricing of water rather than a problem with the rich.  Allow every customer to use/purchase a certain quantity of water at baseline prices and then have the price scale as you use more of it.  At some quantity you could even have the costs for additional marginal quantities of water exceed the 
market clearing price and use the extra funds to buy water from other states or whatever.
		
 
Based on your logic within the context you provided, I agree as that makes a lot of sense. However, the problem is with the scarcity of the resource, the essential need for it for basic survival and not so much with finding an equitable way of distributing it of which your post is IMO a fine example. In our capitalist society, the more scarce a coveted resource is, the more expensive it becomes, thus progressively leaving the most wealthiest being able to have it.
That principle goes out the door when it comes down to having access to those basic necessities that we, the rich, the poor, the indigent, the homeless all need to survive on, of which water just so happens to be the single most important consumable that we need.
As an aside, don't you think that fellow who stated that "we're not all equal when it comes to water" is a perfect example of having a capitalist mindset clashing with a universally socialist need? Having the need for more water than a penniless guy living in a cardboard box based purely on his superior economic status is to me, displaying the highest level of sheer wealth-induced arrogance and ignorance on his part.
I guess what I'm attempting to convey is that at some certain point in our society, having more money and the luxuries it provides is not going to get those folks everything they want in the way they want it. 
At the least, there are some things in our society that requires having an equal share of no matter the wealth or the lack of it, like the air we breathe and the water we all absolutely need to survive on. 
