[Kalimac]

Minas Tirith could well have large public wells every few blocks or so; I believe quite a few medieval cities had these and while they were dreadful disease-spreaders they were also the best way to make sure that everyone got their share. To be honest I'm not sure how they worked, but they must have had at least a rudimentary idea of how pipes and aqueducts worked - the Romans knew. I picture the Minas Tirith natives as being at an approximately Roman level of technology - speaking as someone who has no knowledge of engineering, I'd still imagine that providing water for a city that's built on a hill would involve some use of pipes and aqueducts.