Vg should be thick other brands might be cutting it with something. Personally i wont put any water in my juice , but if thats what you want to do dont use anything but distilled water. Reason being distilled water is non conductive. It would not be good for your atomizers to use a regular conductive water in the juice. I would start out low also maybe 2% and see how it thin it gets. I wouldn't add more then 10% at a maximum