Water filtering
Link dump
Small scale DIY
Charcoal/Sand/Gravel in a plastic drink bottle
https://waterfilterguru.com/how-to-make-a-homemade-water-filter/
Carbon and heated coil, 2 stage filter
https://www.youtube.com/watch?v=2fr5TjZK4ZQ
Berkey bucket filter system, high volume but requires the proprietary Berkey filter elements
https://www.instructables.com/DIY-Berkey-Water-Purifiier/
Another Berkey bucket solution
https://preparednessadvice.com/an-inexpensive-water-filter-the-bucket-berkey/
Bucket system with a ceramic filter kit
https://alaskabode.wordpress.com/2017/05/01/how-to-build-a-gravity-fed-water-filter-for-under-60/
Permanent, for the home
5 stage system for the home, as an alternative to Reverse Osmosis
https://www.youtube.com/watch?v=WCC4TOYYGF8
Interesting permanent solution for the home involving two sediment filters (20 and 5 microns) followed by a carbon filter
https://www.best-osmosis-systems.com/diy-whole-house-water-filter/
Advanced inline 'Big Blue' system for the whole home. High tool, skill, materials dependency
https://www.instructables.com/Changing-Your-Whole-House-Water-Filter/
Water purity
Good overview of what the various filtering systems remove, thus was level of purity can be expected