Distilled water is much easier to get hold of compared to a reverse osmosis system. I suspect most people can buy distilled water, but can’t access a reverse osmosis machine.

Also it’s easier to be confident that your distilled water is still mostly pure as the manufacturer will be regularly checking their output. Unless you’re running regular testing on your reverse osmosis equipment, and cleaning it and the downstream pipes, then how you be certain about the purity of your home made water?

If you are doing all that work, then home made purified water from a reverse osmosis setup is probably as good as store bought distilled water.

If the nurzle for your RO spigot got contaminated with something that liked noses after being shoved into somebody's drink... it might start growing up there. I prefer to only fill the bottles with boiling liquid when dissolving the salt. I use a water boiler. Then you have to wait for it to cool. 20-30 sec in the microwave will bring it back to head temperature.

What I REALLY would not use is an old Britta that's been accumulating goo for the last year. Fungus is bad, hard to kill, and will eat your brain. Do you have sourdough, kombucha, or any other weird smells in your fridge? Keep it outta there!

If you just boil the water before use (and let it cool, obviously!), there's zero risk of infection. Distilled water is generally just the easiest and simplest way to do it safely.

> I always assumed it was to avoid potential bacteria, amoebas, etc.

You nailed it. Misuse can be fatal due to proximity to the brain.

I'm not particularly paranoid, but I do notice mineral buildup over time from tap water. In fact, my dishwasher may be end-of-life because of it.

(and of course, as others have said, bacteria, amoeba, disinfecting chemicals, minerals from the house's pipes... did I mention that I'm not paranoid? :) :) )

But YMMV -- if you're happy with reverse osmosis, go for it.

you can use home RO if you boil it but distilled is best. I used to work in industrial water purification and I would never use water that hasn't been boiled first.

edit: and yes... look at the news every now and again where you hear of some kids swimming in a lake and dying from an amoeba or something else that jumped the brain barrier.