I bought and installed an under sink R/O (reverse osmosis) unit in my kitchen -- it uses a separate spigot. It makes 99%+ pure water from my well-water which is run through a sodium-ionization water softener first.

It actually tastes better that most bottled waters and the filters are about $45 a year to maintain. It makes 4L to 5L a day and cost me $225+the installation (part of a kitchen refresh (new water softener, counter tops, sink, faucet, this R/O unit, and a new dishwasher)).

Amazon sells these units -- that's where I got it -- the local plumbing supply wanted $320 for it BTW.