17 Jul

Coffee Water: A Conversation with Keefe Aldstadt

written by: Tyler Bruno

In the upper left corner of Texas is a company that specializes in the filtration of water. The company is Optipure, and the man I’m talking to today is a fella named Keefe. I’ve run into Keefe at many a coffee event and we always set loose plans to sit down and “really get into this water thing.” The specialty coffee industry is putting a well deserved effort into understanding the mass complexities of water, and I wanted to get as close to the source as possible to see what more there is to learn. This is the record of meeting, and I hadn’t the slightest clue as to what I was in for.

“You can’t really assign numbers to water.” Mr. Aldstadt tells me in a sterile conference room with short, astro turf like carpets. “Baristas always want to set numbers to everything, but water is more complicated than that.”

“Yeah but can you give me any sort of number or basis to jump off?”

I sit there with a “Barista Camp” notebook open to a white page, hoping to jot down a few magic numbers, learn some secret alchemy about the universal solvent, and go on to impress my fellow coffee friends with my newfound wizardry.

“No, not really,” He says.

Somewhere, a balloon pops.

“But what about 150 Total Dissolved Solids (TDS)? That’s like the gold standard right?”

“Not necessarily”

And we’re off.

This is going to be a six hour conversation in where I realize a harsh reality about water, coffee, and the universe at large: There is still so much stuff we just don’t know.

Keefe is a fairly humble person and will be the first to tell you that his knowledge and scope is very limited, which is the only non-intelligent thing I’ve ever heard him say. He’s an incredibly smart human man and will lay waste to your brain with the amount of knowledge he has inside of his.

“The only thing we technically do to water is remove taste, odor, sediment, and introduce minerals if we need to,” He tells me.

“And that’s what’s supposed to be so complicated?”

He just laughs, the way a barista would laugh if someone who’d never pulled a shot suddenly asked for the chance to pour one of those ”leaf things.”

Displayed in the conference room is a unit where you can spin a dial with your finger and land on whatever TDS you want. I ask why every cafe in the world doesn’t have one.

“Because it’s not so easy.”

SCAA guidelines for “Coffee Water”

Assuming you have a brief understanding of ideal coffee brewing water (and if you don’t, these brilliant minds will give you the low down—  ), here’s the lightning round on Optipure’s approach to coffee water.

No Two Things are Alike

Not all municipalities have the same water, to say the least. In some cities, you would need to introduce minerals like calcium and magnesium (what we refer to as hardness), and in some, you would need to remove a lot of hardness. Some water may naturally have the correct amount of alkalinity (40ppm, respectively), while some have practically none, or far too much. So in short, dialing in your Total Dissolved Solids means nothing if we don’t know which solids we’re dialing in, and moreover how those solids will react to everything else.

Everything is Connected

“Water is holistic,” Keefe tells me after hour three. “Everything affects everything else.”

He explains that if your alkalinity is too high and you need to remove some for the best possible extraction, doing so will also result in a decrease of your calcium carbonate hardness by reaction, which may have been perfect to begin with but will now be too low.

In this sense, natural water is not unlike a series of weighted scales— every time you add something or take it away, the balance shifts. Unless you have in depth information about your municipalities water, how it changes from season to season. For instance, in some eastern US cities, the chloride levels of the surface water goes through the roof late winter when all the salt on the street melts— crazy. So unless you know how to use this information in order to get the “numbers” us coffee people long for, it’s best to get rid of these scales entirely.

Starting Over

Getting rid of these scales is a process known as reverse osmosis, a process that most are probably well aware of. Here’s the benefit: By doing this you are essentially stripping the water until it is nothing more than a fragile shell of what it was. Then, you introduce your “empty” water to only the elements you want it to absorb— limestone for some calcium, some magnesium, a little alkalinity etc. Since it’s empty and starving, the water will absorb everything you give it. We get the TDS we want, and we’ll also know exactly what’s in it. This tends to give a lower TDS then what we know as ideal from the SCAA chart above (around 70 TDS rather than 150 TDS). Keefe tells me that this is okay and at the moment, I believe him.

Plus, he’s about to give me the big twist.

The Twist

As the sun sets out the window and we begin wrapping up our conversation, Keefe gives me a “this call is coming from inside the house” moment.

“Just to wreck your mind,” he says.

He shows me the SCAA guideline for 150 TDS, and then, has me focus on the small print: Calibrated using 442.

He explains that there are three types of calibration for a TDS meter. There’s

NaCL, which measures the sodium chloride,

KCL, which measures potassium chloride,

and 442, which measures 40% sodium sulfite, 40% sodium bicarbonate, and 20% sodium chloride.

“So what do you calibrate to?”


So between water filtration companies, TDS testers, and water analysts, the same language isn’t necessarily being spoken. That 70 TDS number that comes out of an Optipure RO system? It’s not the same 70 TDS as a 442 calibrated system.

“So it’s more like 100 TDS.” Keefe says, packing his briefcase and closing up the conference room.

“Wait, what?” I say.

He just shrugs and smiles.

“I told you,” he says. “It’s more complicated than you think.”

This conversation could go on forever (and it does here— which I suppose is the whole point of all this.

There’s a lot more to figure out, and talking is a good start.