How much water you consume will depend upon your own body. We are all different - from our genetic makeup to our daily lifestyle and exercise activities. Someone who is 40kg will require less water than someone who is 140kg. Thus, we all require different amounts of nutrients - water included.
As a general rule of thumb, 2-3L is recommended for the average person. If you perform more exercise than the average person, chances are that you will require more water, since you will lose a lot of fluids through sweating. If this is the case, 4-5L per day is still very safe to drink. You may even require more than 5 Litres. Additional water will only assist fat loss and toxin excretion (within reason, of course).
If you are unsure if you are drinking enough water during exercise, try this. Weigh yourself prior to your exercise. After completion, weigh yourself again. If you have lost weight, this will be due to fluid loss primarily through sweating. Therefore you are not drinking enough to sustain your hydration levels. eg. A loss of 500g is equivalent to approximately half a litre of fluids. Conversely, if you gain too much weight, you may be drinking too much. This could hinder your performance during exercise due to bloating.