Comment by traderj0e

To simplify things, "closed loop" shouldn't even be part of the discussion. Usually they just mean a closed-loop cooling system somewhere inside, either to directly cool machines (typically ML) or to cool air for air-cooled machines (standard). That's separate from how you eject the heat from the coolant to the environment. That's either cooling towers (like swamp cooler, uses water), chillers (like A/C, no water but more power), or passive air cooling (like car radiator, no water but only practical if very cold outside).

So you could have a closed-loop water system cooling your machines or chips, but still be consuming water to cool the coolant. And they will advertise this as "closed loop." Better to ask if they have a cooling tower.