I definitely don't trust the municipal water sources + local plumbing my landlords provide to be of the highest quality. I'd like to measure what actually comes out of my taps but I'm not aware of a lab which would affordable do contaminant level testing for just a few samples.
Well, I come from the UK. We don't have the same political issues you do, but to make up for that, we have special problems. While British water is completely safe, there are still some issues...
- ancient Victorian infrastructure means that there are leaks. They're terrified of contaminated water getting into the system, so they crank the pressure up, to ensure that any leaks happen outwards. This, of course, makes the leaks worse.
- even so, the water has to be chlorinated, and in some areas, quite heavily. You will never forget the first time you turn on a tap and get gassed.
- some really old houses still have lead pipes. I was taught as a child that if I wanted to drink water, I should let the water run until it went cold before filling a glass.
- some not-so-old houses still have a low-pressure water system which runs things like hot water, bathroom taps, etc. Traditionally these run off a tank in the loft, filled from the mains. This tank is frequently unsealed, and so fills up with sludge, moths, dead rats, etc. Even today, do not drink water from the hot tap unless it's obviously at mains pressure (which means it's connected to the mains via a sealed high-pressure water tank or a heat exchanger). (The reason for this is to enforce a vertical drop between the water mains and the house system, so that if the pressure ever falls in the water mains, there's no risk of sucking contaminated water back up the pipe. In such houses, there is a single source of potable water, which is the cold tap in the kitchen.)
- even then the water out of some of the aquifers is so hard as to be nigh undrinkable. Soap works markedly better in Scotland than it does in south-east England, and if you go to Cambridge you might as well not wash.
Of course, a lot of this is now being fixed, although slowly and painfully --- I think lead pipes are now no longer a thing. But it really makes me appreciate how good the water is in Zürich.
This dual-system is one of the things that drives me crazy when in the UK. Oftentimes you get a sink with two separate taps, one hot one cold. So if you want to rinse your hands with warm water, you turn them both on and quickly move your hands between the two. If you're too slow, you get scalded!
Fun fact: mixer taps in the UK don't mix! There are two separate tubes, usually one inside the other, for carrying hot and cold water. So, what comes out of the tap is cold on the outside and hot on the inside, resulting in scalding your hands and freezing them at the same time!
...because you can't connect the hot water and cold water systems together (because of aforesaid risk of sucking contaminated water out of the hot system into the cold system).
Agreed - These are even worse than the dual-taps. It looks like you can get warm water out, but as you said, when you put your hands under the tap you're getting independent streams of very hot and very cold water. Strange (and painful) sensation!
There's been a lot of work to get rid of all the lead pipes, but there are still plenty around. Also, DIYers sometimes use the wrong, lead-based, solder for water pipe.
I definitely don't trust the municipal water sources + local plumbing my landlords provide to be of the highest quality. I'd like to measure what actually comes out of my taps but I'm not aware of a lab which would affordable do contaminant level testing for just a few samples.