Water: The Most Important Liquid in Our Kitchen


Nothing passes our attention in the kitchen, including the water we drink and use for cooking. Berkeley tap water is pretty good, but it’s not perfect. That’s why we enlisted the help of David Beeman, aka The Water God. He has set up the very first direct-reuse reverse osmosis water filtration system right here in our kitchen. Not only does it filter out impurities from the city water, but it also adds back a proprietary blend of minerals to the water at an optimal concentration for both flavor and culinary use. Plus, our filter system does it all with absolutely zero waste.


Reverse Osmosis: Many of us associate water filtration with cylindrical charcoal filters that spit flecks of black coal into the water. These filters get some things out of the water (like chlorine), but they are far from the ideal filtration system. Instead of these old-school filters, we use reverse osmosis for the water at Mission: Heirloom. Reverse osmosis is a water purification system that uses a special membrane to separate out impurities from tap water. After running through the membrane, the water is filtered through a series of activated carbon filters to remove any remaining contaminants.

Zero Waste: In most reverse osmosis systems, the water that doesn’t pass through the membrane is thrown off as waste. Instead of ditching all of that water down the drain, we mix that excess in with our tap water and then recirculate it back into the reverse osmosis system.

Coconut Shells: We also use organic coconut shell carbon instead of the usual mix of coal and plastic in our filters. These coconut carbon filters are just as effective as the coal-based filter, but they’re 100% biodegradable and free of any plastic-based toxins.

Optimized Minerals: Once the water has been filtered, we always add back minerals (mostly potassium and calcium) into the water. Why? It tastes better. Plus, the water is better for our bodies and it allows us to maximize the extraction of goodies when we make our coffee, tea, and bone broths.

Copper Pipes: Our water is transported via copper pipes. It’s brand new and doesn’t leach chemicals like vinyl chloride into the water like PVC. We have a couple of taps right by the stove to make it easy to bring out delicious water into our cooking pots.

Perfect Water: We had our water tested by some of the wisest minds in the coffee business, and they declared it the most perfect water they’d ever tasted! Their support gives us 3rd party verification for all of these steps that we’ve taken to clean our water supply.


Our water system is complex and, frankly, pretty expensive. Luckily, you can get clean water even without installing your own reverse osmosis machine. To do so, we recommend investing in a SOMA water filter. Each SOMA system is beautiful and effective. Our friend David Beeman helped design the filter, so you know it’s good. SOMA uses the same coconut shell technology that we do in each of their filters, and their filter has has been gold-certified by the Water Quality Alliance. If you choose to make a purchase with SOMA using this link, you can even get a free filter! (We want to note, however, that while happily recommend SOMA’s product, we receive nothing in return from their company.)


Understanding Reverse Osmosis: In order to fully understand how reverse osmosis purifies water, it is helpful to learn how osmosis works. Osmosis describes the process by which water moves across a semi-permeable cell membrane from solutions containing low concentrations of dissolved particles (solutes) to solutions containing high concentrations of solutes. For example, imagine a cell that is full of super salty water. If that cell is placed in another solution that is contains less salt, water from the outside will move into the cell in order to dilute the water in the cell, just as you would add additional water to a salty soup to make the overall soup less salty. Once the water inside the cell has the same concentration of salt as the water outside the cell, water will stop flowing into the cell. At this point, the cell and the surrounding water have reached osmotic equilibrium.

Given no outside forces, osmosis will always happen when the opportunity presents itself, and it will continue until both solutions are at equal concentration. However, if enough pressure is exerted on the highly concentrated solution, osmosis can be halted and even reversed. We take advantage of this condition in reverse osmosis. In reverse osmosis, tap water or any other contaminated water is pushed at super-high pressure (above 500 psi) through a manufactured semi-permeable membrane. Because this pressure is higher than the osmotic pressure, pure, solute-free water easily rushes through the membrane.

Downsides to Reverse Osmosis: Because so much pressure (and so much water) is required to blast the pure water out of the membrane, reverse osmosis systems waste quite a bit of water. Some systems take as much as 4 or 5 gallons of contaminated water in order to produce 1 gallon of pure water! Another problem that can happen with reverse osmosis is that the filtered solutes can back up on the membrane, forming what is called “scale.” Once these solutes form scale, they can gum up the membrane and degrade the material. Additionally, the completely pure water that results from reverse osmosis isn’t that beneficial, plus it doesn’t taste great. Beverages, bone broths, and soups all benefit from being made using water that isn’t completely pure. The trick is to control what we put back in.

Beneficial Minerals: We worked with David Beeman to optimize the minerals we add to our water. Our mix of (mostly) potassium and calcium is added back to the water at 150 parts per million (ppm). At this concentration, the water tastes better better and its minerals are easier for our bodies to absorb. We’re also adding back minerals at a very specific concentration that is optimal for cooking as well as brewing coffee and tea. For example, when making bone broth, it is best to use water like ours because it leaves room in the water to absorb the minerals, gelatin, and collagen from the bones. Similarly, water for coffee needs to include the right balance of minerals to complement and enhance the flavor of the coffee beans.

Making a Zero-Waste System: The biggest difference between our reverse osmosis system and what you’d normally see at home or in a coffee shop is that ours doesn’t waste anything. Called a direct-reuse system, it collects and recirculates the excess waste water by reincorporating it with the water coming in from the tap, which we use in our washing sinks. Anytime anyone turns on the sink, it dilutes the higher concentrate water, reducing the proportion of total dissolved solids in the mix. Since the high concentrate water is constantly being diluted, it never has a chance to build up enough minerals to form scale on the membrane. Plus, we’re not dumping gallons and gallons of water down the drain!


One response to “Water: The Most Important Liquid in Our Kitchen

  1. Hi,

    Personally, I like reverse osmosis system. And I have installed such a filtration system. And now I have enough clean and healthy water to drink & cook. Before that, my tap water tasted and smell bad. Thanks for my RO unit.


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