A few years ago, I tested my well water and compared it to James Hoffman's recommended solubility reports and realized that the only thing that my water needed was to run it through a carbon filter. For my well water that worked really well. But when I lived on municipal, I had to get distilled and I followed a few recipes, and selected the one that tasted best to me.

It really depends on your water. You can either get the report from your municipality for the general water in your location, or you can have your water either professionally tested or buy a kit online and test it yourself. Then match the sediments and makeup to a recipe. Make a few, get the ingredients (those are normally super cheap), mix, taste, adjust, and use the one that you like the best.

To avoid having to descale your machine too often, try not selecting a recipe that is too hard.

Ultimately, though, it's whatever it tastes best for you.

Edit. Spelling.

I've played around with water twice, most recently within the past couple of weeks.

My house has well water which is very clear and refreshing, but relatively hard. We have a water softener, so what comes out of the tap has 0 hardness.

That doesn't mean there's nothing in it, just no calcium (or magnesium, I think).

My water is also pretty basic (high pH).

Soft, basic water can lead to boring coffee from what I've read.

Most recently I followed the instructions at Barista Hustle to make my own water using distilled water, baking soda, and epsom salt.

I'm loving the espressos I'm getting, so the next thing for me to do is switch back to my well water and see if gets noticeably worse.

To answer your question, though -- it depends on your water.

Look for a water report from your municipality. If things are pretty reasonable, a filter may not change your coffee game.

I've heard that RO filters are the best type, but you may end up removing too much good stuff. In that case you can re-add your own minerals to taste.

I live in a place with very hard and nasty water. I've been using the zero water pitcher filter and it's unbelievable. It basically filters everything when to 0tds and is perfect with my espresso machine since there's very minimal scale buildup. The water tastes great too, basically like absolutely nothing.

I asked the same question a few years ago and ended up buying a water distiller. Much less wasted water, and doubles as a nice space heater in winter. It's much cheaper than a RO system, convenient enough for espresso (I make 3l of pure water once every 2-3 weeks) and unlike RO systems, doesn't need costly consumables and maintenance. It only needs descaling once in a while like a regular kettle.

Then I remineralise it with one of these recipes: https://www.baristahustle.com/diy-water-recipes-the-world-in-two-bottles/