As above, deionised or boiled water would have been perfectly ok to tie you over, until you could get a bottle of G13 if you mix two different types of base coolants they can cancel each other out and stop the coolant working properly, really bad idea. Also putting water straight from the tap is an equally poor idea and unless you want a coolant system full of green slime in a few weeks, if I was you I'd do a flush with deionised only then you want a 50/50 mix of G13 and deionised water it's actually cheap and quick(ish) to do