Depends the time of year and whether I'm working or not. In the summer at work I'll easily drink 5-8 litres of water per day, and I'll be using the toilet every 30 minutes or so for a quick splash.
In the winter on a day off I'll drink 2 litres or so, probably only visiting the toilet once every 4 or 5 hours. As mentioned already, tea and coffee are diuretics so you'll use the toilet more often. Diet also plays a big part obviously.