Making sure a spirit tastes the way the way it should at its final ABV is one of the most important jobs of any distiller.
The quality of your proofing water—as experienced distillers know well—can be the difference between an exceptional product and a stack of customer complaints. That’s why it’s vital to use water that won’t degrade the flavor or appearance of the final spirit.
For most distillers, this means using the purest water because dissolved solids and salts in water can cause unwanted flavor changes and hazes that make customers wary. Unfortunately, most water sources have significant deposits of those unwanted compounds. While standard water treatments remove some of them, such treatments are far from sufficient.
That’s why you’ll need to perform your own water purification if you want suitable proofing water. There are a couple of ways to go about it.
Making sure a spirit tastes the way the way it should at its final ABV is one of the most important jobs of any distiller.
The quality of your proofing water—as experienced distillers know well—can be the difference between an exceptional product and a stack of customer complaints. That’s why it’s vital to use water that won’t degrade the flavor or appearance of the final spirit.
For most distillers, this means using the purest water because dissolved solids and salts in water can cause unwanted flavor changes and hazes that make customers wary. Unfortunately, most water sources have significant deposits of those unwanted compounds. While standard water treatments remove some of them, such treatments are far from sufficient.
That’s why you’ll need to perform your own water purification if you want suitable proofing water. There are a couple of ways to go about it.
[PAYWALL]
RO Water
The first type of purification that can be used for proofing water is reverse osmosis, or RO.
RO is a type of membrane filtration that uses high physical pressures to overcome the osmotic pressure of water, producing a permeate stream of ultra-clean water. RO is effective at removing bacteria and viruses from water, and there are even filter systems capable of removing particles as small as 0.0001 micrometers. That level of filtration allows distillers to remove unwanted ions, such as calcium and sulfate, which are known to cause hazes in distilled spirits, even at very low concentrations.
RO systems are very simple to operate, and many are built without moving parts to reduce maintenance costs. You can size them for different flow rates and, because you can store RO water, many distillers opt to save money by buying smaller systems and pairing them with neutral holding tanks. That customizability has made RO by far the most common type of proofing water at distilleries large and small, and many distillers consider it to be the gold standard.
Unfortunately, though, RO does come with some problems of which you need to be aware.
First off, RO systems are not cheap—even the smallest system can be priced prohibitively. Furthermore, the membranes in RO systems are extremely delicate and prone to degradation if exposed to compounds such as chlorine or oxidizers. That means that for RO systems to work effectively, they often need to be paired with a carbon filter system that removes any hazardous chemicals before they reach the membrane. Those filtration systems add even more cost.
Many environmentalists also consider RO systems to be wasteful. Besides the “clean” permeate stream of water they produce, they also release a “dirty” concentrate stream. The amount of concentrate released by RO systems varies greatly—it depends on the incoming water chemistry as well as the distiller’s own parameters, but the amount is often significant. In fact, there are distilleries that currently operate with permeate concentrate ratios as high as 1:1, meaning they are effectively rejecting half their incoming water. Of course, that also means they’re drawing twice as much as they need, causing water costs to skyrocket. While some distillers have found alternative uses for that dirty water, most have to dump it down the drain.
Finally, another problem with RO systems is flavor. Pure water is great at dissolving things—especially flavor compounds. And because RO is as close to pure water as most systems can get, it can pick up unwanted flavor easily. Those unwanted flavors can come from anywhere, including your own process piping. Talk to any experienced distiller, and they’ll probably have a story about how just a few drops of leftover spirit in a tank or a fresh rubber gasket on a hose caused an entire batch of RO to become unusable.
That’s why it’s incredibly important to handle RO with care.
DI Water
The second type of water purification system that some distillers use for proofing water is known as deionization, or DI.
DI water has been chemically treated to remove all dissolved ions. That is accomplished using chemical resins, and the distiller can choose from two main types of those.
The first type of resins are known as acid cation exchangers, sometimes referred to as water softener resins. They’re effective at removing compounds that have a positive charge, such as magnesium or iron, from the water.
The second type are known as base anion exchangers, sometimes referred to as dealkalizing resins. These are effective at removing negatively charged particles, including nitrates and sulfates.
Most distillers use a combination of both types of exchangers to purify to their desired water profile, and some companies sell mixed-bed systems that allow this to be accomplished in a single tank.
DI systems have recently gained popularity among some distillers because they’re reliable and allow for high flow rates with very little back-pressure. That’s important for distillers who don’t have enough water pressure to operate RO systems effectively or need high flow rates. DI systems also typically don’t need very large footprints and are relatively inexpensive, which is important if you’re a smaller distillery just starting out.
While DI water systems have gained in popularity, there are also a few drawbacks to know about. The first and most important is that ion-exchange isn’t effective at removing noncharged particles, nor is it effective at removing bacteria and viruses. So, if a water source has an organic compound issue or becomes contaminated with bacteria, the water will no longer be potable, and you’ll need another form of filtration before you can use it.
As with RO systems, DI water systems also have discharge issues: For the exchange resins to work properly, you need to periodically regenerate them—a process that sometimes requires strong chemicals. That produces a waste stream of liquid that needs to be managed appropriately, either by working with a chemical removal company or the local wastewater authority.
Finally, DI water can sometimes have a distinct smell or taste to it that can translate over to your products. While there’s no consensus on how to fix that problem—nor on whether it even really exists—many distillers have taken to adding a carbon filter after their DI systems, as that seems to mitigate any off-flavors.
Storing Proofing Water
You can store either RO or DI water before using it for proofing. However, storing large amounts of stagnant water for extended periods presents a serious biological risk.
To mitigate that risk, many distillers install UV sterilization systems on their holding tanks. UV sterilization is a relatively straightforward technology; it involves exposing water to enough light from a specialized ultraviolet radiation–producing bulb, destroying any biological contaminants. That’s normally done by pumping the water through a specialized glass tube that has the UV bulb installed in the middle of it.
The biggest advantage of UV sterilization is that you don’t need to add anything to the water, thereby preserving its clean flavor. The biggest disadvantage—because it doesn’t have a lasting effect—is that you need to constantly cycle the water through the light, to ensure that it remains uncontaminated. That can be very energy-intensive. Furthermore, the bulbs only have a limited number of working hours before they burn out, so they need to be replaced regularly.
Regardless of how you ensure the sterility of your proofing water, it’s important to remember that no water has indefinite shelf life. Over time, both RO and DI water will become acidic thanks to CO2 dissolving from the atmosphere. That acidity can affect the final flavor of a spirit and make it unpalatable. Always be sure to check the flavor and smell of any water that’s been stored for an extended period to ensure that it remains suitable for proofing operations.
The Stuff of Life and Great Spirits
Selecting the right water for proofing is critical to your success as a distiller. Without the right water quality, the flavor and clarity of spirits can degrade noticeably.
Here we’ve focused on the two most common methods for producing proofing water, but there are other alternatives you could consider. Indeed, there are some distillers who have such good water coming from their local taps that they do nothing at all, and they simply add it directly to their spirits.
No matter your own situation, it’s important to evaluate and analyze any water you intend to use for proofing, to ensure its suitability. As the old saying goes, an ounce of prevention is worth a pound of cure.
