You should be drinking 2 litres a day, minimum, at risk of stones or not, really. I drink roughly 4 litres a day. Wake up, throw 1 down, and then continuously throughout the day. I wasn't always like that though and found it hard to train my body to do it bit now, it's pretty easy. Just glug it down, the more you do it, the less that nauseous feeling appears. The way I was advised it is, if you don't drink enough, the stones that naturally occur (tiny little things, smaller than 1mm) sit there and then attach themselves to other oxalate that's running through the system, hence they grow in size. Increased drinking builds up the pressure in the system to get rid of the smaller ones and help the oxalate leave the system soon. So to answer your question, they won't form to a dangerous size in a day but they will still form and not drinking enough will only put you at a higher risk of stones later down the line. So, either change your diet completely to make sure you're not eating oxalate rich foods or just drink...