As stated, water coming from a tap in a commercial establishment is safe to drink. Along the Camino, fountains / fuentes that are safe to drink are generally labeled as mentioned above "Agua Potable' va 'No-Potable.'
The stretch of the Camino from Carrion de los Condes to perhaps Moratinos is bereft of potable water. Also, I do not recall bars / cafes along this stretch.
While there ARE fountains / fuentes along this route, most derive from shallow wells or springs that have been contaminated by agricultural runoff or fertilizers over the years. DO NOT TAKE THE CHANCE. The municipal supplies are safe however.
I always recommend that people obtain and carry extra water at Carrion de los Condes, before they cross this stretch of the Meseta. It is NOT the Sahara Desert or Death Valley! However, it is a broad, flat, unshaded agricultural area with little shade and no opportunities to refill water bottles. During the summer months, temperatures under the bright Spanish sun can exceed 40 degrees (c). Do not forget a broad brimmed sun hat too!
When I depart Carrion, I typically have a full load of two liters in 4 x .5 liter bottles, PLUS another 2 - 3 1.5 liter bottles, strapped to the top, bottom and in the side mesh pockets of my rucksack. The extra, while heavy at first, is used to help other pilgrims along the way who did not get the memo...
All said, I would point out that this remains my favorite stretch of the entire
Camino Frances. I can do some of my best thinking out there.
Hope this helps.