I drink about the same as Bob...2 1/2 litres - 3 a day.
One who has diarrhea and not taking in food or adequate supplementation can run the risk of electrolyte imbalance by drinking too much water.
As well, to much water can exacerbate diarrhea...something that can be helped by lowering intake and increasing fibre supplements.
Balance ....one can defintely take in too much water. Yes, it's good for the skin and body.
Too much water is hard on the kidneys. Especially if forcing large quantities in a short period of time...consistently....
People who drink water constantly and don't have diarrhea can actually dilute electrolytes to a dangerous level.
I did find when I was working full-time that I got a weird headache around 2:00. 2 glasses of water did help it ease...interesting. ..although I did need an Anacin chaser. ;-)