Comment by jeffbee

Some quick napkin math using averages (data center designs vary). One of Google's larger and thirstier data centers, in Oklahoma, is said to use 833 million gallons per year (that's about 2500 acre-feet, in useful terms). It occupies about 250 acres, most of which looks to be parking lots but whatever. The number of households that can be supported on 1 acre-foot per year ranges from 2 to 6 depending (Las Vegas on one end, San Francisco on the other).

You said apartments specifically and this urban form usually starts at 50 dwellings per acre, minimum, which would lead me to say the apartments use more water. The break-even point in this equation is 2-5 households per acre.