Sorry for the delayed response
@Diogo92. I found the amount of water I needed depended entirely upon the weather. When it was very hot I needed to refill my bottles regularly, but when I was walking in the rain I needed little water (although I probably should have taken more). Personally, I don't like the bladder system and I used two 750 cl bottles. I carried one hanging from my bum bag and the other lived in the side pocket of my pack. With a bladder one can't tell how much water has been used and how much remains and it is necessary to remove your backpack to refill.
We split the stage between Azambuja to Santarém and arranged for Mario to collect us from Morgado. It was very hot walking these days and it would have been difficult to walk the full distance in the heat of the afternoon. Mario stopped to offer water to several pilgrims after he picked us up. We returned to Morgado the next day to continue the walk to Santarém in the fresh morning air. In cooler weather it would have been ok to walk the full distance in one go. I would say to walk that full stage in hot weather one would need more than 1.5 litres of water and there are very few opportunities to fill up, and none on the second half of the stage.
For anyone interested in Mario's pick and drop service take a look at my
blog post for this stage, or check out this
thread regarding the possibility of shorter stages between Lisbon and Porto.