When doing the Camino on warm/hot days I drink a minimum of 6-8 liters of water. And no I do not have "to go" all the time. The body uses the water as gasoline while walking. It keeps the body hydrated... If you do get dehydrated it is VERY difficult to get back in shape quickly.
Also if I do not drink this much water when walking all these kilometres, I will have pain and feel tired and not be able to enjoy the camino as much...
This is why I carry a CamelBak on the Camino. I do not mind carrying it. I've done it on all trekking trips before the camino and on the camino and I will probably continue doing it.
People I met on the Camino who had musclepain in the evening and at night did not drink much water... and I met many who had become dehydrated as you walk in the sun all day...
It is not a question of feeling thirsty... when you feel thirsty it is allready "too late" - dehydration has begun... the trick is to drink small sips all the way. Kidneys can handle that much better than drinking half a liter at every fountain.
But, this is just the way I do it

- this works for me...