I use a steel kettle and about 1/3 of my pour-overs are with a Stagg X dripper that is steel.

I already used very soft water, aiming for 50Gh and 15Kh in the water I prepare. Would distilled-only be a higher risk to etch minerals out of a steel kettle and dripper?

Today, I tried distilled-only and it was same to better than the same coffee the day before where I used my normal water. Since it was a bit a tastier and it would be one less chore, mixing water, to do, I would continue to try distilled-only if the risk of etching out minerals or other compounds from my kettle or dripper is not increased.

We've used RO water for many years in our stainless steel kettles. There's no evidence of pitting, leaking or corrosion at all. RO water isn't quite the same as distilled, but close enough for me to opine that you'll have no problems at all. Moreover, our kettles always look brand new, with no trace of any scale.

Thanks for the reply. It is probably not a problem, and the water I normally use is very soft. I will explore more to try to find an answer so I am more comfortable, as it made very good water and would get rid of a monthly chore.

Acavia wrote:... Would distilled-only be a higher risk to etch minerals out of a steel kettle and dripper? ...

Yes, that's chemistry, but I wouldn't worry about it. After a couple years, my Stagg EKG developed one pinpoint pit in the stainless steel bottom when I was using double-distilled water. The pit only bleeds what I presume is iron oxide when I use distilled water but is invisible when using any other water. Eventually the kettle may develop a leak there - maybe in a few year/decades if I had kept using distilled water. I haven't done the corrosion chemistry math, and won't .

Nunas wrote:We've used RO water for many years in our stainless steel kettles. There's no evidence of pitting, leaking or corrosion at all. RO water isn't quite the same as distilled, but close enough for me to opine that you'll have no problems at all. Moreover, our kettles always look brand new, with no trace of any scale.

Same. When I recently got back into espresso, I was surprised at all the dire warnings to not use RO water. I'm doing the RPavlis method now for my machine, but I'm not convinced it's completely necessary. FWIW, our RO system does have a remineralization stage that increases pH a bit and adds back in a slight amount of minerals, but the water is still only 6 ppm.

baldheadracing wrote:Yes, that's chemistry, but I wouldn't worry about it. After a couple years, my Stagg EKG developed one pinpoint pit in the stainless steel bottom when I was using double-distilled water. The pit only bleeds what I presume is iron oxide when I use distilled water but is invisible when using any other water. Eventually the kettle may develop a leak there - maybe in a few year/decades if I had kept using distilled water. I haven't done the corrosion chemistry math, and won't .

A bit of rust coming off of stainless steel is an indication that it needs passivation. It might not have been cleaned properly at manufacture before passivating, or a ferrous utensil may have scraped the surface and deposited some iron particles. Normally, nitric acid is used for this commercially, but that's dangerous stuff. You can do it at home using citric acid and waiting a longer time for the process to occur. Home brewers do this all the time, and you can google home brewing passivation and come up with a lot of instructions and videos, such as this one http://www.youtube.com/watch?v=tjgNI8CLIhE