I only saw one font labelled 'no-purificado', which is not the same as non-potable, between SJPP and Pamplona. I don't recall seeing any font labelled 'non-potable', but I wasn't making a point of checking this. I always carry a pack of water purification tablets when I am travelling, but don't recall having to use them at all in Spain. I suppose if I had been desperate and had to collect water from a stream or pond, I would have done so. It just wasn't necessary. I didn't buy bottled water and had no gastrointestinal issues because I was using taps and fonts.