Is there a difference/preference as to which "type" of water is used; tap, bottled, DI?

I always use distilled. Any minerals dissolved in the water are going into the engine, and I don't see how that can be good.

also you dont want a clogged filter in there

any concern on leavin water in the system if the car will sit over a lengthy period of time...

Re: Water Injection
 

if its distilled water no, it will just evaporate, and condense as temperature changes if its a closed system. if its tap or anything like that when it evaporates it will leave behind deposits from any minerals in the water. Keep in mind most drinking water has minerals added for taste, when the water is evaporated by combustion, or just sitting it WILL leave behind calcium and any other minerals that were in the water.

Re: Water Injection
 

just wonderin if evaporation condensation promotes rust if you have water moisture exposed to internal metal parts..