I can't drink enough water!

We are advised to drink two litres of water in a day. I manage to drink one litre of water during work.

Once I get home I am really thirsty and

would continue to drink water but I find that if I drink anything past 6.00pm I am up during the night running to the toilet.

So how do I fit my two litres of water in during the day and why can't I continue to drink water at

night time?