Well, unless you take care of condensing issues your pc will be short lived.... Tap water is way colder than roomtemp and hence will cause condensing on your block and possibly tubing.. That, and possible corrosion (not rust, unless you plan on using iron blocks (do that even exist???)), but if you use aluminium that shouldn't be a big issue, copper is slightly worse me think.. or is it the other way around??..
Anyway.. yes, it'll work.. and it'll have quite a flow speed so 1/2" ID, and whilst you're at it I'ld cool the rest of the components aswell, though.. that means more insulation and more care taken to counter condensing issues..
-bubba