I bought a half build home with wiring already run. It has 10-2 wire running to the hot water tank location. My question is do I need 10-3 run to there or is 10-2 O.K? Can I make the white wire my red wire? Or do I have to have a neutral?
Usually checking the manufacturers instructions and your local authority will answer that. I've heard of some (actually, only once...I think the inspector was 'off base'...where was I suppose to attach the neutral wire??) jurisdictions requiring 10/3, but most dont. Tape/paint the white wire black at boh ends and you should be all set.
Just because you can, doesn't always mean you should