Don't use distilled water. Water is actually a very strong solvent and chemical compound, it hates not having dissolved salts in it, so when you put it into your body it will suck out anything it can get - sodium, calcium, magensium, etc. That's why you shouldn't drink it. In large quantities it will strip you of salts and can fuck up your bones & teeth.
Get some sodium chloride or BAC water made for injections, it is cheap and easily available. And yes you can leave it a day or longer reconstituted, refrigerate it.