Can you add water after the yeast has started it's work? I am not sure that I have a full five gallons in there now and would like to make up the difference. I think that I lost more during the boil than I thought.
You could just do it real Carrillo. Although you could just let it go and add it by boiling your priming sugar in a bit more water and adding sterile boils water. You could even boil your sugar normal and a separate pot of h2O and boil that then add when cooled until topped off. You will just be raining the volume and diluting a little should be for though make sure you give it a gentle stir in bottling bucket or rack onto of the water already in there.
On Deck: Undecided
Primary: Cal Common 'Steam' Beer
Bottled: Ginger Porter, BirthdayIPA
Previous Brews: Everyday IPA
Yes you can. It needs to have been boiled and cooled. Personally, I wouldn't water it down though. I'd rather have a little less of a stronger beer than accidentally end up with something with no body or flavor.