Hi Jane,
On the Portugues camino, I was drinking the local tap water at first, filling my bottle at bars,etc but did not feel 100%, so after a few days, changed to bottled water, and felt better. The change in water with its different minerals, salts etc can have an effect,if not used to it, so now on camino, we always buy big, inexpensive bottles and transfer this to our smaller bottles. Hardly ever drink the fountain water, unless I've run out, tho some people do, and have no problem. A young Dutch peregrino we walked with for 5 days, (to Finisterre) was often very ill, and he was constantly drinking from fountains. I wondered about that. :roll:
Hope this helps. Buen camino. Carole