It's not the same but it's not that different. Bac water has a preservative added to it to make it last longer. Bac water can be used for a month after your first use due to the preservative. Sterile water can only be used once and whatever amount you don't use you need to throw out the vial. Basically you end up wasting a lot of sterile water but it's cheaper so you have to figure out what's best for you. For hgh I'm sure bac water will make more sense.