Depending on where you live, you could have great tap water or terrible stinky tap water. Generally, developed countries (UK, Ireland, etc.) have better quality tap water (due to better infrastructure, cleaner working conditions, etc.) but it could even vary between whether you’re somewhere rural or urban. If the tap water doesn’t make you sick, doesn’t look muddy, doesn’t smell, etc. you are probably fine (and if you’re extra-cautious, you can test tap water for concentrations in certain minerals and such). You can always grab a water filter if your tap water is bad.

If you’re wondering how tap water can stay clean, there are a bunch of steps to treat unclean water. There is coagulation, which clumps dirt and other particles into larger, easier to remove particles using various chemicals. Then there is flocculation, which makes the particles even bigger, turning them into “flocs”, through mixing. Then there is sedimentation, which is basically where the flocs are so big they sink and form a sediment at the bottom. After that, you have filtration (which removes even more particles) and disinfection (which uses UV light, chlorine, or similar to kill microbes). I had to search for the specific words (coagulation and flocculation in particular), but I do remember the actual steps from geography lessons.