Why can we not use deionized water?

I just received my Anova immersion circulator, and was looking at the manual and it mentioned to not use deionized water. Why is that? I tried looking on Google and could not find any relevant information.


I know a bit about water since I have a high end espresso machine. With an expensive espresso machine you want good water. The problem with RO or distilled or deionized water is that there are no solutes in the water (no minerals etc). So the water essentially “wants” something in it. It will literally eat away metal. I have an RO system in my house, and that’s why all the tubing in the RO system is plastic or silicone and not copper. If you use hard water you will get a scale build up. I am using softened water from our faucet. No scale build up and no degradation of the metal.

Interesting. Thanks for the info!

Also, as an aside RO/deionized/distilled water is not good for coffe or tea. Tastes bad compared to water with some minerals.

Re: mineral content in water

Same basically holds true for brewing beer, and I would guess wine as well – although oenologists spend far less time talking about water than zymurgysts do. In wine, it is probably more or less the same thing as terroir… the distinctive taste a specific range of land leaves on the grapes. However, with grapes the water and mineral content are taken in vascularly instead of as a chemical additive when brewing a wort.

Dozens, perhaps scores of times, I have had a discussion with another brewer about my Newcastle-style brown ales. It is a notoriously finicky recipe to get right, and it is the mineral content of the water which matters. (No recipe on hand now, but I think it is natron – or soda ash – which is in fairly high concentrations in Newcastle… and without it you’ll never achieve the same chewy texture.) There are other examples, but none other so dramatic so far as I know.

The bit about DI water causing a greater corrosive effect is interesting. Never really gave that much thought.

For the same reason @rbh1515 stated, you should not drink distilled water. It “wants” minerals so it will leach them from your body.

Wow, diet water :slight_smile:

Water is the universal solvent. Deionised/distilled water is its strongest form.