Take a 2 litre bottle of water/juice/squash to work every day.
Have a quick swig each time you get in the van.
1st week, probably struggle to finish it in a day.
2nd week on, it'll be gone by lunchtime.
4 wees a day is fine.
As already posted, needs to be straw coloured at worst. Lighter-fine. Darker, you're dehydrated. You'll end up with kidney stones/problems/failure if done regularly.
Not enough wees? Bad back? Could be kidneys...
I have about 4 or 5 coffee's or tea's, berocca in 1/2 pint of water in the morning and 2 litres of flavoured water (it's essentially squash without colour), seems sufficient to me.
(I do get some grief about my caffeine intake from my brother-in-law though)