Who gets to determine how the resources are allocated? Everyone does, thanks to their actions in the free market. 

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How does a libertarian allocate it? By respecting property rights, so the owner of said resource is the one who would decide how to allocate, based on the market. 

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Simply price? Yep, price and demand. 

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 Who gets to handle the faucet? The owner/owners 

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Is anyone guaranteed water? No, well at least if we are seeing this thought a libertarian point of view, no, nothing can be guaranteed, anything can be earned. 

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Are you a libertarian? Have you read Ayn Rand?

Because I believe this is an interesting ideology and I have learn a ton from Ayn Rand.