The tap water in Barcelona and Madrid is graded as ‘potable’, meaning it is fit to drink. There are public fountains dotted around both cities, especially in Plazas, where you can refill your water bottles. Spain is a hot country and good access to fresh water is considered a neccesity rather than a luxury.
Some of the fountains are gorgeous and have legends attached to them. For example, if you drink from the Font de Caneletas in Las Ramblas of Barcelona it is said that you will return one day.
Also this is the spot where, when Barça win the football, the football fans head here to celebrate.
Curiously football in Spain tends to be a fairly peaceful event. While you might want to avoid turning up in your Real Madrid shirt to a celebration at Canaletas, the feeling amongst Barça fans and football matches is relatively peaceful and calm. Go to see Barça play at the Camp Nou and you’ll be surrounded by families. Sure some fans are pretty rowdy but that seems to be the limit, unlike some countries where football can be an excuse to get physical.
Back to the water… Barcelona’s water is quite heavy in calcium so, as long term residents here, we filter the tap water via a jug which reduces the ‘cal’ and also the chlorine which can be a bit much. I would however recommend to visitors or anyone with a sensitive stomach to play it safe and buy bottled water, and minimise the risk of losing precious days.
After all, you’re here to enjoy the sights of the city.