I have drunk the water in Spain.. ( Barcelona, Tossa , and Majorrca) with no ill effects,, and in all places in France ,, south , east , north or south.. never had an issue.
There are two points to ponder. First.. sometimes we attribute an illness to water but it could easily be anything we ate .. and secondly, some people are super sensitive to even different mineral contents in water and can get upset tummies from drinking water in their own countries but in different regions.
The sickest I ever got( and I was sick sick sick ) was from eating in a dubious place in Rome.. only had the one meal.. lunch, had only had tea and toast for breakfast that day.. went out for lunch, and then no appetite for dinner and that night then ALL night and ALL the next day was violently ill.. I knew I shouldn't have eaten at that scuzzy place in Rome,, the waiter even had his thumb in my food when he carried it over,, blech.. lol good times good times.. at least experienced first hand the lovely Italian hospitality at the Argritourismo we stayed at that night and day outside Florence.. desk clerk and maid checked on me all day bringing me juices and broth.. and my poor 11 yr old with me lunch and dinner .. to the room.. She wasn't ill , just stuck with me. Ps we both drank the water so I know it was what I ate.. a salad.. she had spaghetti.