despite this question being asked several times on the forum, I can't seem to find a good answer anywhere for an optimal remineralization stage "filter" for an under sink RO filter. I don't need to plumb, I just want to make consistently good water for espresso that won't cause scale. Based on what I see, it seems like I need more Mg and K than Ca for cations, but most options I see are predominantly Ca.

I would really appreciate any help!

Google Barista Hustle water. Their process is pretty simple and cheap if you start with mineral free water e.g. distilled. No calcium means no scale.

Thanks for sharing! I guess I was hoping to just add something in line because we use the RO for drinking water too. Currently have a mineralizer off amazon that makes good tasting water with fairly low hardness, but there's Ca in there, and I want to avoid scale if possible. Seems like an opportunity for someone to make something for us "normal" coffee people that also satisfies our "abnormal" spouses.

I've order these to try. I'll test my water when they arrive

https://thirdwavewater.com/collections/espresso-profile

Sgoldberg89 wrote:Thanks for sharing! I guess I was hoping to just add something in line because we use the RO for drinking water too. Currently have a mineralizer off amazon that makes good tasting water with fairly low hardness, but there's Ca in there, and I want to avoid scale if possible. Seems like an opportunity for someone to make something for us "normal" coffee people that also satisfies our "abnormal" spouses.

Due to the ratio of water to coffee in espresso, the concentration of hardness doesn't affect the extraction nearly as much as it does with drip/pour over/batch brewing. Calcium carbonate in concentrations of 70ppm or less, and assuming a neutral to basic pH as a starting point, will not scale your machine all that quickly. After about four or five years you may need to descale the machine. Most Calcite filters, though, will only reach 40ppm concentration, absent any plumbing gimmicky that manipulates the pressure, contact time (flow rate), or pH of the feed water.

Have you tested the mineralizer water? Some of those cartridges on Amazon contain various salts, some of which could be corrosive to your machine. Calcium Chloride, as found in several commercial remin systems, doesn't precipitate out at temperature. It is however corrosive and will damage the boiler eventually.

I haven't tested it - but I'm going to just get one with Calcite. I didn't realize that softer water with lower [Ca] would suppress scale accumulation. This is super helpful. I just got an iSpring filter based on a rec from a fellow HB-er to add onto my APEC RO system. Hopefully that gets me close enough. I don't have enough space or credits with my wife to start another science experiment at home to make the ultimate water 1 gallon at a time. Someday, hopefully, but not today. Thank you! Any other recommendations are welcome!

FYI, the iSpring cartridge is suspect. I haven't called them about it, they do have a phone number, but they don't list the minerals and it could contain chlorides which could damage your machine.

An Omnipure K2548, is an inexpensive inline calcite filter you can find online for $15-20. Just be sure the verify the plumbing connection as they come in many different types, i.e. 1/4", 3/8", threaded or push connect.

Sgoldberg89 wrote:I haven't tested it - but I'm going to just get one with Calcite. I didn't realize that softer water with lower [Ca] would suppress scale accumulation. This is super helpful. I just got an iSpring filter based on a rec from a fellow HB-er to add onto my APEC RO system. Hopefully that gets me close enough. I don't have enough space or credits with my wife to start another science experiment at home to make the ultimate water 1 gallon at a time. Someday, hopefully, but not today. Thank you! Any other recommendations are welcome!

It doesn't suppress scale accumulation, it's merely slower. The rate of scale accumulation is based on several factors, mostly concentration/saturation level and pH.

Thanks for the advice re iSpring. Was too late the cancel the order but I'll look closely at the packaging when it arrives for indication of Cl-. I'm starting residency next year and won't have too much time to dedicate towards espresso but give me 5 years and an attending salary, and I could see myself building a platform for people to plug and play with the promise of ideal espresso water. Would be good to have different formulary options too for people who have different tastes for ionic concentrations and contents similar to the Barista Hustle. Grateful for this community!