I remember from Family Guy Peter had flung some "holy water" onto a guy and her screams as if it was sulfuric acid, then you see a clip with a scientist and he sasy, "'Holy water'? Where the acid I ordered?"
IMO, it suggests that the "holy water" is acid; it's flung onto people when Christians are pissed with, wouldn't you agree?

well, christians who are pissed with people throwing holy water, better than throwing rocks i say, less harmfull

I now recall a friend of mine, he went on holiday to spain, and this woman sold holy water.
so he bought a vial, drank it and started playing like he was suffocating.

this woman threw on more holy water, pointed the cross in his face and said prayers, to the point he and some friends around started laughing and the woman kinda got pissed off for being ridiculed (reasonable tho)

but yeh, i remind that episode :P silly mix ups

Holy water is highly contaminated, so I've heard.

Partially true, did some googling and found the Daily Mail article (which other articles cite as source).
Considering newspapers don't always take scientific research/data as it is, I did search for the research papers. Found it posted on several sites, but the full paper isn't available unless you're a member of such things.
As such it's not something they just cooked up, here's the article: http://www.dailymail.co.uk/health/a.....ul-health.html

However, because there's no mention of how many and where they did these tests in the abstracts of the papers, and the article says only 21 holy springs in Austria were tested, stating that all of it is highly contaminated simply holds no ground. The only thing you can truly say is that only 14% of the tested Austrian springs (which would be 3 springs) are up to drinking water standards.