For other natural resources, sure. But without water humans _die_. That's not subjective.
I think it would be perfectly reasonable to assume that agricultural water from individual farms dwarfs that of individual residences, so you just need to find the cutoff at which residential allowance stops applying.
As a bonus, not using all that water to grow artichokes leaves more water for people to drink.
So, yeah. Like samatman said, "Let's try making it efficient first, and then see if we need to add equity."
You were defending a market-based solution to water usage, which I asserted would be inequitable and therefore immoral.
Flow restrictors are pretty anti-market, and I think they're a great solution to penalizing those who repeatedly break the rules.