One system that most probably have never heard of is a reverse osmosis system that is made for aquarium use. Something like this:

https://www.amazon.com/dp/B0043FYJ8M/?tag=aquariumadviser4-20

It runs off of household water pressure rather than a high pressure system. Can generate 50 to 100 gallons per day of RO water. I used to have one when I kept marine reef aquariums. Yes it does require water pressure which may or may not be available. Something to think about though.