Why JCWS Is Different
We Passed That Exit An Hour Ago
The Juliet Coffee Water System (JCWS) is as different from anything you can buy off the shelf for a coffee shop as a T-rex is from a chicken. It is the result of a batshit crazy obsession with precisely making water for coffee at scale.
What makes JCWS so goldang special? It comes down to repeatable quality of precisely dosed water at any volume, from 0.5L to all-day busy-coffee-shop scale.
1. Architecture
A Pump For Every Pump Job
Most water-for-coffee systems use either municipal water pressure or 1 pump to get their RO system working a little better.
The JCWS skid uses three separate pumps: — RO high-pressure feed
- UV recirculation / transfer
- distribution to the bar
These pumps allow extraordinary control over each stage of the treatment system, from providing the optimal pressure across the RO membrane to radically increasing the accuracy with which it can dose, to feeding the espresso machine (a SanRemo Cafe Racer) at the sweet spot of its pressure demand band.
Separated Tanks
JCWS uses two stainless buffers (aka tanks). One tank is for raw permeate (RO cleaned water) and a separate one is for fully treated product.
On top of the three big pumps, JCWS uses three Grundfos DDC 6-10 metering pumps, each one dedicated to dosing a specific thing into the treated stream.
Division of Standards
A great water system should produce water for all your needs, not just the espresso machine. Since most coffee shops offer iced drinks, making excellent ice is part of what a water system should do. The ice machine should not have to drink your espresso recipe. In JCWS, a valved branch sends UV-treated RO permeate straight to the ice maker, bypassing mineral injection. This keeps ice clear and clean, which is how ice should be.
Overspec As Standard
All of the hydraulic pumps are overspec'd relative to typical cafe duty, usually by a factor of 2-3x. This means they can run cooler for way longer, and if we ever add in more filtering or treatment, we'll never have an issue with getting the water where it needs to go.
Having this amount of control over pressure, storage hygiene, and which loads get which water is something municipalities and industrial loops do. It is not something most cafes do.
2. True High Pressure RO
In the world of RO you'll hear about permeate, which is the water that permeated through the membrane and is clean. The "other" water that doesn't make it through is the waste, also called brine, concentrate, reject, or drain stream.
The first hydraulic pump drives water through the RO membrane at much higher pressure than standard municipal line pressure. Municipal water pressure is often in the 40–80 psi range. That's not enough for high performance RO.
Without going deep into mass-transfer math, RO is materially more efficient when you operate the membrane up in roughly the ~175 psi class — well within what this pump and the Filmtec XLE Pro-2540–class elements we use are built for. A few high-end packaged systems do something similar; most cafe skids do not.
Running high pressure on big membranes means you're wasting far less water and the membrane is working much less hard.
JCWS uses a large scale (2540) RO membrane, the Filmtec XLE Pro-2540. 2540 refers to the size of the membrane cylinder; 2.5" x 40". A 2540 has a surface area of about 29 square feet. Compare this to a typical under-the-sink membrane of 1.8" x 12" (1812) with a total surface area of 4 sq ft , and even your typical 2521 unit (that you'd find in a large cafe) only has 13 sq ft of surface area.
Larger membranes offer significant advantages when well operated:
- A higher recovery rate, meaning they produce more permeate and less waste per unit of feed water
- Longer life
- More resistant to fouling
- The Filmtec also delivers superior salt rejection due to the membrane chemistry, ≥ 99 % NaCl
Basically, a bigger & higher quality RO membrane gives you options to generate higher quality water with less waste, but... ya gotta have the pumps and the architecture set up for it.
The design intent is to create near-blank permeate. That way what you taste in the cup is the coffee, not the distortions of city water.
3. Precise Control
Individual metering pumps inject magnesium sulfate (sweetness / clarity), calcium chloride (body), and sodium bicarbonate (buffering). We could also swap out any other salts, but those are the standards and produce superb water for coffee.
The metering pumps we use (1 pump per solution) are rated 0.1–100 mL/min each, with 1000:1 turndown. This is the equivalent of dosing as low as two tiny drops per minute (think standard medical dropper) into a continuous defined stream.
Rather than adding a pinch of salt to a gallon and shaking it up, hoping you get great distribution and that you're not off by a gram, the JCWS metering system gives you exactly what you ask for.
Because we're also using the larger distribution pumps to move water past the metering pumps at specific and defined flow rates according to programmed logic, we have extraordinary control over how much water flows through the pipes and gets dosed.
Compared to a dissolving cartridge of minerals that may have channeling, uneven flow rates, or even run out without you knowing, this level of precision and control is on the level of NASA-level telemetry vs a 1998 Honda Accord.
Hondas are great cars, but they won't get you to the moon.
The combination of precise dosing and precise water flow is what control means here: you are not adding in a cartridge and hoping it's close enough for your washed Ethiopian vs the co-fermented Guatemalan you just ran.
JCWS allows you to change the active recipe targets for the final water, including different end uses (espresso, drinking water, matcha, etc.) on the fly to exactly what you need.
Want to nudge sulfate a few ppm relative to the last roast? The path is precision dosing, not pinch 'n pray.
By contrast, a typical hand or cafe recipe is in the range "0.25–0.5 g of the first two salts" and "a pinch" of bicarbonate. Pinching is for grade school, not excellent coffee at scale.
This is not to say you can't make excellent water at home, or in small batches. The Bluewater, Coffee Chronicler, and Michael Cameron's Holy Water are all proven recipes for excellent water.
What JCWS allows is successive, programmable, precise, batches (as small as 0.5L!) without syringes and gram scales, where each liter takes about 16 seconds to produce, and total TDS coming out of the mixer is verified in real time before it gets to the espresso machine.
16 seconds per liter for precisely executed water recipes is unmatched outside of JCWS.
4. Instrumentation and obsession
The JCWS tracks everything in the system in real time, including pressure drop across the membrane, permeate and feed conductivity / TDS, temperature, and the pressure the espresso machine sees.
You don't do that if you "kind of" care about doing a good job. Wherever there is an opportunity to make something better, cleaner, or more functional, JCWS takes it. Here's UV sterilization as an example:
UV Sterilization
Tank 1 is not passive storage where water just sits stagnant. Permeate is continuously recirculated through a generously sized UV unit on P-102 so water in the tank remains clean, exceeding the USEPA-grade UV dose (16 mJ/cm²) by ~7× even towards the end of the lamp life (see System overview, §2.2 / §3.5).
JCWS doesn't just produce clean water, it constantly keeps it in optimal condition.
Most water systems might report the water pressure and TDS coming out the far end, and those are the high end ones. Tracking what each stage does (and whether or not it's working the way it's supposed to) is the hallmark of industrial process control.
If you want reliably superb water for coffee, nothing less will suffice.
That drive for reliable excellence, backed by blood & treasure, is what makes JCWS a worthy obsession.
Happy watering!
Shoutout to PK for guidance throughout the design and build of JCWS. Pretty much every excellent detail was thought of by him, backed by a couple of decades of experience in the world of membranes. Thanks dawg!
For the full flow diagram and component list, start at JCWS system overview.