​Potable Water Regulations

The United States Environmental Protection Agency defines potable water by a set of www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations 90 contaminants: epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations.
The bottled water industry has additional standards that are regulated by the U.S. Food and Drug Administration (FDA) and defined by Current Good Manufacturing Practice” (CGMP) regulations specific to processing and bottling drinking water. These CGMP regulations include:
  •  Water must be sampled, analyzed, and found to be safe and sanitary.
  •  Bottled water processors are registered with the FDA as a food facility, and specific plant and equipment design, bottling procedures, and record-keeping procedures must be met.
  •  U.S. Code of Federal Regulations 21CFR165.110 also defines labeling on bottled water.

​Potable Water Chemistry

The taste of water is impacted by minerals, also known as ionic compounds or salts. In water, the desirable minerals that influence taste disassociate into positively charged cations of calcium (Ca+2), sodium (Na+2), and potassium (K+) and the negatively charged anions of carbonates (HCO3), Sulfates (SO4), and Chloride (Cl) [1]. For this reason, many global drinking water taste standards are based on the content of these minerals. While lower concentrations can create neutral-tasting water, higher concentrations can be more desirable until they are not. It's worth noting that the taste of water is subjective, and any parameters mentioned are generalizations within the safe limits of drinking water.

General Measures of Mineral Content
When measuring mineral content, specific and general measurements are helpful when trying to understand the taste of water. The vital general measurements of mineral content include Total dissolved solids (TDS) and Hardness, and Total alkalinity/carbonate hardness which is the combined concentration of carbonate and bicarbonate expressed in CaCo3[2].

Minerals that Influence Taste

  • Anions
  • Cations
  • Non Soluble mineral
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Soluble Minerals
Calcium (Ca+2)
  • Taste: Bitter, sour [7]
  • TTC: 100–300 mg/L [1]
  • Common in bottled water: <100 mg/L [3]
  • Common in water at levels found in saliva.
  • Common forms [1]:
    • Calcium bicarbonate Ca(HCO3)2
    • Calcium Sulfate CaSO4
    • Calcium chloride CaCl2

Sodium (Na+2)
  • Taste: Salty [8]
  • TTC: 200 mg/L [1]
  • Range in bottled water: 10-1200 mg/L [3]
  • Optimum concentration: 125 mg/L for distilled water
  • Common forms [1]
    • Sodium sulfate: Na2SO4.
Potassium (K+)
  • Taste: Salty-bitter, salty-alkaline [9]
  • Common in bottled water: <5 mg/L [3]
  • Common forms [1]
    • Potassium carbonate KHCO3
    • Potassium sulfate K2SO4
    • Potassium chloride: KCl

 Magnesium (Mg+2)
  • Taste: Bitter or salty-bitter [9]
  •  TCC: 100–500 mg/L [1]
  • Common in bottled water: <20 mg/L [3]
  • Common forms [1]
    • MgCO3: Magnesium Carbonate
    • Mg(HCO3)2: Magnesium bicarbonate
    • MgSO4: Magnesium sulfide
    • MgCl2: Magnesium chloride
Carbonate (HCO3)/Bicarbonate 2(HCO3).
At neutral pH, bicarbonate is more common than carbonate and helps keep cations in solution, whereas at higher pH, carbonate increases and lowers dissolved CO2 levels [2].
  • Taste: Typical mineral tart taste
  • Common in Bottled Water: 50-200 mg/L [3]
Common forms [1]
  • •Calcium bicarbonate: Ca(HCO3)2
  • •Sodium bicarbonate: Na2CO3
  • •Sodium carbonate: NaHCO3
  • •Magnesium bicarbonate: Mg(HCO3)2

​Sulfate (SO4)
  • TTC: 200–400 mg/L [1]
  • Sulfate also suppresses magnesium and reduces the effects of calcium.
  • Common in bottled water: <100 mg/L [3]

​Common forms [1]
  • CaSO4
  • Na2SO4
  • MgSO4
  • Al2(SO4)3
  • K2SO4
Chloride (Cl)
  • Taste: Bitter tasting
  • TTC: 200–300 mg/L [1]
  • Increased chloride levels in water, in the presence of sodium, calcium, potassium, and magnesium, can cause water to become objectionable.
Common forms [1]
  •  NaCl
  •  CaCl2

Nitrate (NO₃-)
Caused by the breakdown of organic materials, these ions in high concentrations pose a toxicological concern because human gut bacteria or prolonged warming of nitrate-rich food can convert them into the more toxic nitrite (NO₂-).
​
Non Soluble mineral
Silca [3]
Taste: None influences texture as it is not soluble in water.
Common in bottled water: <20 mg/L

Iron [1]
  • TCC: 0.1–1.0 mg/L.
  • Most iron drinking water standards are 0.3 mg/L because of laundry staining, turbidity, and color formation, but iron can also impart a bitter or metallic taste.
  • Other soluble minerals
​Copper [1]
  • TTC: <1 mg/L
  • Gastrointestinal issues if >4 mg/L.

Zinc
  • TTC: 4 mg/L
  • Common forms [1]: •ZnSO4

Manganese [1]
  • Taste: Astringent
  • TTC: 0.05 mg/L

​Other Factors Influencing Taste

​As Whelton (2009) and Mascha (2006) differed in the ideal range of some dissolved ions, we have provided both for reference.
  • Vintage
  • pH
  • Temperature
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Vintage [10]
Mascha, in Fine Waters, notes that “vintage” (the age of the water) can influence TDS. This occurs as younger water has less time to absorb minerals, the age of water is less critical than local geology, and that vintage is primarily helpful for a good backstory.
pH [1]
Water pH strongly influences drinking water taste, with tap water pH typically being 7–8 but varying from pH 5–11.

Defining pH
Pure water containing no dissolved minerals has a pH of 7, which is the definition of a neutral pH. Kunze in Technology Brewing and Malting explains that a portion of pure water electrolytic dissociation where H2O ↔ H+ + OH-. Then, because 1 liter of water at 25°C contains [9]:
  • 10-⁷ H+ ions and 10-⁷ OH- ions pH is 7.
  • An equal number of hydrogen ions (H+) and hydroxyl ions (OH-), the pH is neutral.

For more on pH: LibreTexts. (n.d.). The Hydronium Ion. In LibreTexts Chemistry. Retrieved from
chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Acids_and_Bases/Acids_and_Bases_in_Aqueous_Solutions/The_Hydronium_Ion
​Influences on water acidity
  • Carbon dioxide lowers pH (increased acidity) because CO2 + H2O = H2CO3 (carbonic acid). H2CO3 then disassociates into a hydrogen ion (H+) and a hydrogen carbonate ion (HCO3-). This is why increases in CO2 cause ocean acidification. For more on the pH of water concerning CO2: Atlas Scientific. (2021, October 7). How Does CO2 Affect pH In Water? Retrieved January 3, 2024, from https://atlas-scientific.com/blog/how-does-co2-affect-ph-in-water
  • Dissolved minerals help to offset/buffer the acidity of water if due to dissolved CO2. For this reason, naturally carbonated mineral waters are historically coveted [11]. Similarly, neutralizing filters containing calcite or ground limestone (calcium carbonate) or magnesia (magnesium oxide) are used to raise the pH (more alkaline) [2].
  • Pollutants can increase acidity, which is less common in well-treated municipal water.
pH influence on taste
Wheaton (2009) notes the following influence of pH on the taste of water
  • Desirable pH: 6.5–8.5 (avoids a bitter taste).
  • Metallic taste: <pH 6.5
  • Slippery feel or soda taste: >pH 8.5.

FineWaters.com [12]
  • Acidic: pH 5-6.7
  • Neutral: 6.7-7.3
  • Hint of Sweet: 7.3-7.8
  • Alkaline: 7.8 to 10

pH Influence on Bicarbonate concentration
Water pH can also influence bicarbonate and carbonate levels. HCO3 –/CO3 –2 influence taste by combining with cations (e.g., NaHCO3, Mg(HCO3)2, Ca(HCO3)2 , CaCO3, MgCO3, K2CO3, and Na2CO3).
Temperature [1]
Water temperature influences taste intensity and an individual’s degree of liking for water; however, the specific temperature is a matter of personal preference.

Wheaton (2009)
  • Tap water: Varies between 4–60°C.
  • Ideal drinking water temperature is cooler than body temperature, specifically 15–25°C (59-77 °F).
  • FineWaters.com Recommendations
  • Mascha’s recommendations are based on the thought that if “Served too cold, the bubbles can be overwhelming.”
  • Still Water: 54 °F
  • Effervescent water (0-2.5 mg/L CO2): 56 °F
  • Light sparkling (2.5-5 mg/L CO2): 58 °F
  • Classic sparkling (5-7.5 mg/L): 60 °F
  • Bold sparkling water (7.5 mg/L): 62 °F

Sources of Water

​Surface water
Municipal sources of surface water [13]
Surface water is found above ground, typically in lakes, rivers, and streams. It is used in many regions like Southern California as a potable (drinkable) water supply. However, as surface water typically contains higher microbial, organic matter, and particulate content, it must undergo treatment to be suitable for human consumption. Traditionally, this is done through a series of steps.
  • Sediment removal
  • Disinfection
  • Water Reclamation 
  • Non-municipal surface water
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Sediment removal
  • Coagulation: The water is treated with positively charged aluminum or iron salts. These bind to dirt and other negatively charged particles, helping them to coagulate.
  • Flocculation is then performed by gently mixing the water to form larger, heavier particles called flocs.
  • Sedimentation is when the flocs drop out of solution and settle to the bottom of a sedimentation area because they are heavier than water.
  • Filtration in water treatment often involves multiple filtration media due to the wide range of particulate sizes of dust, dirt, and microbial contaminants. For example, water may initially pass through gravel, which traps large particles, then sand for smaller ones before passing through activated carbon.
Disinfection [14]
Chemical Disinfection
Chlorine, chloramine, or chlorine dioxide neutralize microbes like parasites, bacteria, and viruses in the water at the treatment plant or that may be introduced into the water from the pipes.
  • Chlorine is traditionally used, but if the water has higher levels of dirt or pathogens, it can be quickly used up to the extent that it may be insufficient for disinfection by the time it reaches the end of the pipes. Chlorine also produces small amounts of trihalomethanes (disinfection by-products); at elevated levels, THMs have been associated with adverse health effects [15].
  • Chloramines are a group of chemical compounds that contain chlorine and ammonia. They may be used instead of chlorine because chloramine lasts longer in water pipes and produces fewer disinfection by-products. The drawback is that chloramine treatment is more expensive than chlorine [16].
  • For more on the differences between chlorine and chloramine: Centers for Disease Control and Prevention. (n.d.). Water Disinfection with Chlorine and Chloramine. Healthy Water. cdc.gov/healthywater/drinking/public/water_disinfection.html
​
Non-Chemical Disinfection
  • Ultraviolet (UV) light or ozone can help to minimize chlorine usage at the treatment plant. However, these technologies do not continue killing germs as water travels through the pipes between the treatment plant and your tap.
For more on ultraviolet disinfection:
U.S. Environmental Protection Agency. (1999, September). Wastewater technology fact sheet: Ultraviolet disinfection.
Retrieved from www3.epa.gov/npdes/pubs/ozon.pdf

For more on ozone disinfection:
U.S. Environmental Protection Agency. (1999, September). Wastewater technology fact sheet: Ozone disinfection.
Retrieved from www3.epa.gov/npdes/pubs/ozon.pdf
Water reclamation using ultrafiltration, nanofiltration, and reverse osmosis

For wastewater to be used as a potable water source, water will be additionally filtered to a micron level of 103–106 daltons or lower, with ultrafiltration being the first step and reverse osmosis being the second. Only water and small molecules like salts and tiny, charged molecules can pass during the ultrafiltration step.

​For more on water reuse: 
U.S. Environmental Protection Agency. (2023, October 31). Water Reuse Information Library. Retrieved January 23, 2024 www.epa.gov/waterreuse

More on public water treatment
Centers for Disease Control and Prevention. (2022, May 16). Water treatment. Retrieved from www.cdc.gov/healthywater/drinking/public/water_treatment.html

Surface Water Sources used in the Bottled Water Industry Other than municipal water that has been treated, special surface water may be used. These include:
Rainwater [17].
  • Collection Region: Regions with low air pollution
  • Harvest Technique: Immediately after it hits the collection
  • surface to prevent contamination.
  • Mineral Content: Low
  •  Nitrate: Typically none.
Groundwater
Unlike surface water on the earth's surface, groundwater comes from under the ground. Aquifers form when groundwater accumulates in quantities large enough to warrant pumping for drinking or agricultural usage.

Groundwater is significantly influenced by geology, as the physical and chemical composition of the rock and soil that water passes through as it travels into the aquifer influences its mineral composition. This is similar to water percolating through coffee during a drip or pour-over process.

Types of Aquifers
  • Unconfined aquifers are those with a relatively permeable layer. This results in higher susceptibility to contamination or salt. For example, groundwater salinity can range from freshwater (chloride concentration less than 250 mg/L) to seawater (19,500 mg/L) [20]. Brackish waterfalls in between. Deep groundwater is more likely to be potable and is located in confined aquifers, better shielding it from contamination.
  • Confined aquifers have relatively impermeable layers like clay or rock, making them less susceptible to surface contamination. These layers function as water-damming strata are non-porous rocks or soils like clay, shale, and dense igneous rock that water cannot pass through. These layers can act like container walls and form the barriers of an aquifer.
Geology of Groundwater
40 CRF 141.2 defines groundwater as “The name of water from a subsurface saturated zone that is under a pressure equal to or greater than atmospheric pressure.” Where: Unsaturated Zone The unsaturated zone is located beneath the soil and contains air and water-filled pores. The aquifer’s water quality is influenced by the water-bearing strata’s chemical and physical composition. Specific factors include:
  • Depth of the unsaturated zone: If the unsaturated zone is shallow, and groundwater is found relatively close to the surface, it is more susceptible to surface contamination.
  • Permeability of the aquifer (the rate of percolation and what peculates through), is influenced by: The size and arrangement of rocks affect their water-holding capacity. Rocks with uniform size and loose arrangement can hold more water than those of different sizes. This is because smaller rocks can settle in the spaces of larger rocks, reducing the open space for water.
  • The shape of the rock. Round particles pack more tightly together than sharp-edged particles, have more open space, and therefore hold more water.
  • The type of rock. This also influences which minerals dissolve into the water.

Saturated zone
The saturated zone exists at the top of the ‘water table’ or ‘groundwater level and is characterized by rock layers that are completely filled with water. Its physical and chemical composition influences the aquifer’s water quality and consists of the following types of rock: 
  • Sand and gravel are composed of silica type rocks and are low in dissolved minerals but more susceptible to contamination from surface sources.
  • Sandstone is made of sedimentary rock, including gypsum. It can have high mineral content.
  • Carbonate rock is composed mainly of limestone (calcium carbonate) and dolomite (calcium magnesium carbonate) and can result in water with high mineral content.
  • Interbedded sandstone and carbonate rock, when combined, result in high hardness and high alkalinity. Burton-Upon-Trent, for example [2].
  • Igneous and metamorphic rocks like basalt and granite are insoluble and produce water with low alkalinity and hardness. An example is the Sierra Nevada Mountains aquifer [2].​
Ground Water Types and Oahu’s Source of Water 
The island of Oahu utilizes groundwater for its potable water supply. The water from rain, fog drip (cloud vapor intercepted by vegetation and subsequently drips to the ground, commonly occurring between altitudes of 2,000 and 6,000 ft), and surface water are saturated into the ground in the Oahu’s watershed areas [21].
These areas are protected from construction to avoid contamination by chemicals. This article uses Oahu as an example for highlighting the different ways to access water and groundwater types.

The following sources are tremendously insightful into Oahu’s water
Gingerich, S. B., & Oki, D. S. (2016). Ground Water in Hawaii. Department of Land and Natural Resources. Retrieved from dlnr.hawaii.gov/mk/files/2016/11/B.17w-USGS-Ground-Water-in-Hawaii.pdf
Board of Water Supply. (n.d.). Hawaii’s Water Cycle. Retrieved from boardofwatersupply.com/water-resources/oahu-water-history/the-water-cycleboardofwatersupply.com/water-resources/oahu-water-history/the-water-cycle
  • Well (General)
  • Shaft Wells and Dike Tunnels
  • Artesian Well
  • Spring Water
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​Types of Groundwater and Wells[22]
Regarding bottled water, Groundwater is defined in the United States Code of Federal Regulations Title 21 Section 165.110 (21CFR165.110) by how it is extracted from an aquifer. The following types of extraction methods generally apply to both bottled water and municipal water, with 21CFR165.110 cited when appropriate.

Well Water Defined
  • Geology: Groundwater is accessed by penetrating a confined aquifer.
  • 21CFR165.110: “The name of water from a hole bored, drilled, or otherwise constructed in the ground which taps the water of an aquifer may be ‘well water.’”
  • Mineral Content: Variable

Municipal well type: Well
Wells are small-diameter holes drilled hundreds of feet below the ground. Pumps extract the water.
Municipal well type: Shaft/ Shaft Well
Created by a mining technique rather than drilling. This causes the well to be significantly larger in diameter than drilled well [23]. Oahu has five, including the Kalihi and Halawa Shaft.
For more on Shaft Water in Honolulu:
Honolulu Board of Water Supply.
(2022, January 5). Halawa Shaft Media Kit. Retrieved January 3, 2024, from
boardofwatersupply.com/mediakit/halawashaft

Municipal well type: Dike tunnel [24]
Dike tunnels are horizontal shafts used to access water from volcanic dikes. On Oahu, these dikes, which trap percolating water in massive vertical compartments that rise to 1,000 ft in elevation, were formed when magma stopped flowing to the surface, cooled, and then formed a dense, nonporous rock in miles-long sheets that rise in the rift zones [24]. Without human intervention, this water escapes when it overflows the walls of the dike or when internal pressure causes leakage in the form of a spring. To access this water at the utility scale on Oahu, horizontal dike tunnels at Waimanalo, Luluku, Haiku, Kahaluu, Palolo, Manoa, Kunesh, and Waianae Plantation. For more on Oahu’s dike tunnels were excavated:

Takasaki, K. J., & Mink, J. F. (1985). Evaluation of Major Dike-Impounded Ground-Water Reservoirs, Island of Oahu. U.S. Geological Survey Water-Supply Paper 2217. Retrieved from pubs.usgs.gov/wsp/2217/report.pdf
Board of Water Supply. (2024, January 8). Waihee Tunnel Tour. Retrieved from
www.boardofwatersupply.com/news-events/speakers-and-tours/waihee-tunnel-tour
Municipal well type: Artesian well [25]
  • Geology: Artesian wells form when pressure is applied to an aquifer by recharging and ground pressure. On Oahu, over-extraction has lowered the water table, which is why many of Oahu’s artesian wells have been capped [25]. It should be noted that an artesian well and a non-artesian well can come from the same water source, which is common on Oahu.
  • 21CFR165.110: "The water from a well tapping a confined aquifer in which the water level stands at some height above the top of the aquifer.” “Artesian water may be collected with the assistance of external force to enhance the natural underground pressure.” This positive pressure can prevent contaminants from the ground or on the surface from seeping into the pressurized aquifer; however, it can be detrimental to the water source as it flows when it is not needed.


Spring water [3]
  • Geology: A spring occurs when groundwater reaches the surface powered by gravity, without human intervention, and typically when underground formation is uneven. As gravity is the driving force of a spring, and the water is coming from an up-hill source, it is imperative to protect the surrounding area, especially up-hill regions.
  • 21 CFR165.110: “The name of water derived from an underground formation from which water flows naturally to the surface of the earth.” “Spring water shall be collected only at the spring or through a borehole tapping the underground formation feeding the spring. There shall be a natural force causing the water to flow to the surface through a natural orifice.
  • The location of the spring shall be identified. Spring water collected with the use of an external force shall be from the same underground stratum as the spring, as shown by a measurable hydraulic connection using a hydrogeological valid method between the borehole and the natural spring, and shall have all the physical properties, before treatment, and be of the same composition and quality, as the water that flows naturally to the surface of the earth. If spring water is collected with the use of an external force, water must continue to flow naturally to the surface of the earth through the spring's natural orifice.”
Mineral water (not necessary sparkling)
Spa in Belgium, Seltser (Seltzer) in Germany, and Epsom in England are towns with famous mineral water.
21CFR165.110: “The name of water containing not less than 250 parts per million (ppm) total dissolved solids (TDS), coming from a source tapped at one or more bore holes or springs, originating from a geologically and physically protected underground water source, may be ‘mineral water.’ Mineral water shall be distinguished from other types of water by its constant level and relative proportions of minerals and trace elements at the point of emergence from the source due to account being taken of the cycles of natural fluctuations. No minerals may be added to this water.”
  • Low mineral content: “If the TDS content of mineral water is below 500 ppm,”
  • High mineral content: “If [TDS] is greater than 1,500 ppm
  • If the TDS of mineral water is between 500 and 1,500 ppm, no additional statement needs to appear. 

Other sources of Bottled Water

Clouds [27]
  • Harvest Technique: In this process, fine mesh nets entrap the tiny drops. This technique is used in some of the driest places on Earth, like the Atacama desert in Chile, where the "camanchaca" fog forms on the shore and then moves inland in the form of cloud banks.
  • Mineral Content: Low.
  • Nitrate: Low.

Deep Sea [28]
  • Geology: Thousands of years ago, icebergs near Greenland melted and sank to the sea floor because their temperature and salinity were different from those of the surrounding seawater. Ice now circles the Earth every several thousand years.
  • Harvest Technique:
  • Natural Energy Laboratory of Hawaii Authority (NELHA), at Keahole Point, Hawaii, provides access to this deep seawater through a pipeline reaching 3,000 feet (914 meters) into the ocean. https://konadeep.com/
  • South Korea, Japan, Taiwan, and China produce refined deep seawater by desalination and re-mineralization.
  • Mineral Content: Deep sea water may contain a relatively high mineral content, including Mg, Ca, Cl, Na, K, Se, and V (vanadium).
  • Condensation [29]
  • Condensation is used in the bottled water industry to create exotic waters from various regions of the planet. For example, Amazon Air Water from Brazil
  • (oamazon.com.br).

Curated
  • Fine Waters uses this term to refer to blends of waters that vary by source and mineral composition [30].

​Carbonated Water

History
Fizzy water, which was historically obtained naturally, has a storied past. Though it is beyond the scope of this article, for more on carbonated water history:
Homan, Peter Gerald (22 September 2007). "Aerial Acid: A short history of artificial mineral waters" idus.us.es/bitstream/handle/11441/39652/109.pdf
  • Flavor
  • Types
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The Flavor of Carbonated Water
There are two general types of unflavored carbonated water: seltzer water and sparkling mineral water.

The taste of carbonation
Chemosensory response: Sour
A 2009 paper by Chandrashekar was one of the first to elucidate the taste of carbonation [31]. The study found that in mammals, carbonation elicits both somatosensory (denotes a sensation, in this case, tingling of stinging) and chemosensory (sense caused by chemical reaction) responses, including activation of taste neurons. This sensation was found to be caused by the sour-sensing PKD2L1-expressing cells acting as the taste sensors for carbonation and showing that carbonic anhydrase 4, a glycosyl-phosphatidyl inositol (GPI)-anchored enzyme, functions as the principal CO2 taste sensor.

Somatosensory response (sensation):
Tingling or stinging
This sensation is directly caused by the carbon dioxide, and is different from the actual physical feeling of bubbles. Wise et al. (2013) [32] found that this perception is caused when CO2 is converted to carbonic acid by the carbonic anhydrase enzyme found in mouth tissue (this enzyme is also found throughout the body and helps to regulate blood pH). The tingle of the painful aspect of carbonation is the acidification of tissue and receptors on trigeminal nerve endings in the oral cavity. It is believed that the particular acid-sensing receptors are those from the TRPA1 (Transient Receptor Potential Ankyrin 1) channels and others from the transient receptor potential (TRP) family.
Influence on water pH

As previously mentioned in the section on water pH, carbon dioxide lowers pH/makes a solution more acidic.

​Influence of minerals
Naturally carbonated mineral waters are historically coveted because the minerals help offset the pH of the CO2.​​
Factors Influencing Bubble Size
  • Higher concentrations of organic salts [33] or substances like proteins and carbohydrates lead to smaller bubbles because these all increase viscosity and surface tension [34]. For this reason, carbonated water does not form foam like sparkling wine and, to a greater extent, beer.
  • Higher concentrations of dissolved CO2 in the liquid result in a higher growth rate of ascending bubbles (and therefore the larger the size of bubbles in the cloud of bubbles following pouring) [35].
  •  Temperature, as CO2 is more soluble in lower
  • temperatures [35].
Soda Water/ Club Soda
Rather than minerals coming from a natural source, as in mineral water, soda water is carbonated with minerals added into the water. Common minerals include Sodium bicarbonate, potassium sulfate, potassium bicarbonate, potassium citrate, and sodium citrate. Unlike in mineral water, the water composition is not listed in soda water.

Sparkling bottled water
21CFR165.110: “The name of water that, after treatment and possible replacement of carbon dioxide, contains the same amount of carbon dioxide from the source that it had at emergence from the source may be ‘sparkling bottled water.’” According to the FDA, sparkling bottled waters may be labeled as ‘sparkling drinking water,’ ‘sparkling mineral water,’ ‘sparkling spring water,’ etc.

​Dilution of Distilled Spirits

  • Proofing
  • Cocktail Dilution
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Proofing
Distilled spirits can be proofed (diluted) before bottling or immediately before consumption. Regardless of the timing, the goal is similar: Adding water reduces the ethanol concentration. This can either increase or decrease the concentration of other aromatic compounds, due to their varying solubility. As a result, the impact of proofing on a spirit’s flavor is not linear. While dilution or proofing of all spirits is typical it is not always performed as the case of “barrel strength” whiskey. As the construct of “opening” aromas with water is most commonly associated with whiskey, academic research has focused on proofing’s influence on this spirit, but it can be extrapolated to other aroma compounds. Key studies in this field include Karlsson et al. (2017) and Ashmore et al. (2023) where it was found
In general
  • “Dilution decreased headspace concentration of hydrophilic aroma compounds and increased concentration of more hydrophobic compounds,” corresponding to more hydrophilic compounds remaining in the liquid [38].
  • Dilution increased the headspace concentration of amphipathic compounds (those with both hydrophobic and hydrophilic components), whereas higher alcohol concentrations retain these in the liquid [39]. As examples of amphipathic compounds include guaiacol, vanillin, ethyl acetate, and limonene, many which are found in whiskey and rum, Karlsson et al. (2017) noted that this may explain why these spirits are often sold at 30–50% ABV (60-100 proof).
Water-to-alcohol ratio
Valcohol x Cinitial = (V alcohol + V water) x C final
V = Volume andC = Concentration/ABV
Additionally
Karlsson et al. found guaiacol moves into the headspace of mixtures that contain up to 45% ethanol, whereas at higher concentrations, like cask-strength whiskey (59%+ ABV), it resides in the liquid portion. Ashmore et al. (2023) studied twenty-five 43% ABV Bourbons, ryes, single-malt and blended Scotches, and Irish whiskies, by chemical and sensory analysis with different whisky/water ratios of 100, 80, 60, and 40% and found:

Bourbon and rye whiskies
• Dilution decreased the primary aromas of “Oak” and “Vanilla” because the associated volatile phenolic compounds are amphipathic (having both hydrophobic and hydrophilic components)..
  •  Dilution increased the prevalence of “Cedar” and “Cornmeal/Cooked polenta,” aromas though the study did not correlate these aromas with specific compounds. However the increase “Cedar” aroma was believed to be due to the hydrophobic nature of many of the oak lactones found in Bourbon, which are often described as “raw wood” or “pencil shavings.”

In Scotch whiskey
  •  Dilution decreased the primary aromas of “Rubber,” “Bacon,” and “Peat smoke,” which are associated with volatile phenols like guaiacol. The decrease occurred due to these phenols' amphipathic nature (having both hydrophobic and hydrophilic components).
  • Dilution increased the prevalence of the “Pome fruit” aroma created by esters derived from acetic acid and fusel alcohols, which were also notably higher in single malt Scotch-style whiskies [22]. They are also relatively hydrophobic compounds, which suggests they are more likely to be repelled by water into the headspace above the sample.
For a more detailed model of the influence of polarity and molecular weight on headspace volatiles due to dilution: Shuttleworth, E. E., Apóstolo, R. F., Camp, P. J., Conner, J. M., Harrison, B., Jack, F., & Clark-Nicolas, J. (2023). Molecular dynamics simulations of flavor molecules in Scotch whisky. Journal of Molecular Liquids, 383, 122152. www.sciencedirect.com/science/article/pii/S0167732223009558

​Mineral content of proofing water
Unlike the water used during fermentation, which may be potable but retains a natural level of Total Dissolved Solids, proofing water is commonly treated using Reverse Osmosis as iron can cause coloration issues. If the same iron is found in fermentation water, it will precipitate and be further stripped out during distillation.
Cocktail Dilution
Influence of water’s dissolved content
Types of dissolved minerals and gases
  • • Lower concentrations of Total Dissolved Solids (TDS) result in a more neutral influence on the cocktail, whereas higher TDS contributes more flavor and potentially provides a point of manipulation of taste. Saline solution is an extreme example. Camper English, in a 2013 blog series entitled the “Water Project,” provides additional guidance, including pairing spirits with water similar to that of its origin: alcademics.com/the-water-project-index.html
  • • Carbonated water helps to aerosolize volatile aroma compounds. This is why effervescent cocktails, like the High Ball, are foundational recipes as noted in A Guide to Cocktail Construction:
    www.hawaiibevguide.com/cocktail-construction.

Ideal spirit dilution range
Up to 35% AVB which is accomplished by adding ~⅛ oz (0.167 oz) of water to 1.5 oz of 40% ABV whiskey. Ashmore et al. (2023) found “dilution past the 80% whisky/20% water level has shown to be deleterious to whisky aroma,” and resulted in the diminishing ability to distinguish between whiskey styles.

Given a small quantity of water causes a significant percentage change, and straws and spoons provide very little control, on-premise establishments can provide guests eye droppers or pipettes.

Frozen water additions to cocktails
It should also be noted that the water in ice will also influence a drink as when it melts, it turns into water. Additionally, ice with lower TDS can be clearer than ice made in the same way with higher TDS. Camper does say in a 2023 blog post entitled “Is Pure TDS 0 Water Actually Bad for Making Clear Ice?” that zero TDS can result in ice freezing too quickly; therefore, some TDS can be beneficial to making clear ice.

For more on ice, read Camper’s book:
English, C. (2023). The Ice Book: Cool Cubes, Clear Spheres, and Other Chill Cocktail Crafts. Indiana University Press.

​Sources and Suggested Reading

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2. Palmer, J. J., & Kaminski, C. (2013). Water: A comprehensive guide for brewers. Brewers publications.

3. Mascha, M. (2006). Fine waters: A connoisseur's guide to the world's most distinctive bottled waters. Quirk Books.

4. Daniels, J. I. (1988). Evaluation of military field-water quality: Volume 4, Health criteria and recommendations for standards: Part 1, Chemicals and properties of military concern associated with natural and anthropogenic sources (No. UCRL-21008-Vol. 4-Pt. 1). Lawrence Livermore National Lab.(LLNL), Livermore, CA (United States). www.osti.gov/servlets/purl/6975363

5. Mascha. (n.d.). Minerality (TDS). FineWaters. Retrieved January 20, 2024, from finewaters.com/the-story-of-fine-water/key-concepts/minerality-tds

6. Whelton, A. J., & Dietrich, A. M. (2004). Relationship between intensity, concentration, and temperature for drinking water odorants. Water Research, 38(6), 1604-1614. Retrieved from academia.edu/67289501/Relationship_between_intensity_concentration_and_temperature_for_drinking_water_odorants

7. American Chemical Society. "That Tastes ... Sweet? Sour? No, It's Definitely Calcium!." ScienceDaily. ScienceDaily, 21 August 2008.
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8. Honig, V.; Procházka, P.; Obergruber, M.; Roubík, H. Nutrient Effect on the Taste of Mineral Waters: Evidence from Europe. Foods 2020, 9, 1875.
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9. Kunze, W. (2014). Technology Brewing and Malting (5th ed.). VLB Berlin.

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11. Center for Agriculture, Food, and the Environment at UMass Amherst. (2007, June). pH – Acidity of Private Drinking Water Wells [Fact sheet]. Retrieved from ag.umass.edu/cafe/fact-sheets/ph-acidity-of-private-drinking-water-wells

12. Mascha, M. (n.d.). Orientation (pH). FineWaters. Retrieved from
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22. 21CFR165.110 - Bottled Water www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=165.110&SearchTerm=bottled%20water

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32. Wise, P. M., Wolf, M., Thom, S. R., & Bryant, B. (2013). The influence of bubbles on the perception carbonation bite. PLoS One, 8(8), e71488. doi.org/10.1371/journal.pone.0071488

33. Gonzalez Viejo, C.; Torrico, D.D.; Dunshea, F.R.; Fuentes, S. Bubbles, Foam Formation, Stability and Consumer Perception of Carbonated Drinks: A Review of Current, New and Emerging Technologies for Rapid Assessment and Control. Foods2019, 8, 596. doi.org/10.3390/foods8120596

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