The old rule of threes is still (roughly) accurate: three minutes without air, three days without water, three weeks without food. But! Some people are particularly freakish/motivated/genetically gifted, as in 22 minutes without air, 18 days without water and 74 days without food (thank you sciencealert.com). Human beings are generally pretty good at avoiding airless situations, and lots of people keep extra food on hand, but for some reason a lot of other people seem to overlook the whole access to water thing.
Stockpiling water is one answer: keep a WaterBOB around for big disasters where you can shelter in place, a Lifesaver jerrycan for when you can GTFO, and things like Datrex pouches, Lifestraws and purifier tablets for everything else. And don't forget the difference between water filters and water purifiers: filters catch the bigger microbes, i.e. protozoa and bacteria. Filters catch those and also viruses, which are much smaller and harder to filter.
If you're looking for a true portable purifier solution that works for everything from foreign travel to backpacking to prepping, the new kid on the block is Grayl with their Geopress. It consists of an outer sleeve that you dip into your water source, then just insert the inner part, press down and you have 24 ounces of purified water at hand. It's easiest when you place it on the ground and use your bodyweight to do the work, but work it does and very elegantly. Remember to turn the cap 1/2 turn to vent before you press.
The $30 filter is easily replaceable after a rated 350 cycles, which should be good for 250L of purified water. Because the outer sleeve separates from the filter insert, it's easy to avoid cross-contamination. Just don't freeze the filter (OK, they say you can do it once), put extremely hot water in it, use soap on the filter cartridge or put any of it into the dishwasher. Aside from those simple caveats the Geopress is plenty tough enough and should last you through many an epic adventure.