Help! I've been transported back in time to London in 1303 AD. After saying hi to the flock of other worldbuilders who have inexplicably travel back in time to Medieval Europe, I decide to set out to get something to drink. Luckily, there are plenty of things to drink in the middle ages.
Three days later, I'm fed up with the fact that all of those things are beer. I'd like to obtain some clean water for drinking and cooking, but the city I'm in is filthy and nobody has any idea why feces and drinking water should be kept far apart. With the rest of the worldbuilders off trying to prevent the black death from happening or giving leaders modern military hardware in order to sway the outcomes of pivotal battles, I'm left to solve my water worries on my own.
What's the best way for me to obtain fresh, safe drinkable water in a medieval city? What sort of technology or resources should I gather to make sure the act of drinking doesn't lead to my horrific demise to one of the many, horrible, diseases that are doing their best to kill my new neighbors?
I'm also a fairly empathetic person, so bonus points of the solution is scalable to the whole city.