The Science of Water

Our experts share their knowledge about the chemistry of water and things that might be in it.

How Hard is Your Water, And Why Does It Matter?

by Kinetico Published 3.10.2016

What Makes Water "Hard?"


Your water is hard when it has minerals dissolved in it. Usually these minerals are a combination of Calcium and Magnesium.  An old way of describing how much hardness there is, is to use "grains per gallon."  If you have five grains per gallon (gpg) and pulled out all the minerals, that amount of hardness would be about the same size as a regular aspirin tablet.  A more modern way to describe hardness is in parts per million (ppm), or milligrams per liter (mg/L).  One grain of hardness is the same as 17.1 ppm or 17.1 mg/L.  I'll use grains per gallon because that's still the convention in North America where I live.

If your water has less than one grain of hardness, it is defined as "Soft."  Water with more than one grain of hardness is "Hard," and can be Slightly Hard (1.0-3.5 gpg), Moderately Hard (3.5-7.0 gpg), Hard (7.0-10.5 gpg), and Very Hard (above 10.5 gpg).  Water that has been treated by a water softener, reverse osmosis, or a distiller will be Soft.

Hardness is important because it prevents soap from lathering, reduces the effectiveness of detergents, and causes crusty scale because those extra minerals can't stay dissolved forever.  As a result, people with Hard water have to use more soap and detergent to get the job done, and appliances (dishwashers, water heaters, clothes washers, etc.) and fixtures (faucets, showerheads, etc.) don't last as long as they should.

How Do We Test For Hardness?


In the Laboratory, we add chemicals to the water that give it color, then add another chemical drop by drop until the color changes.  The number of drops is a very exact way to find out the number of grains of hardness in the water.  This color change test is called "titration."  There are titration test kits available for field use too, and they can be very accurate when you want to know exactly how much hardness is in the water.

In the field we often use a Soap Test to demonstrate the difference between Hard and Soft waters in a dramatic way.  There is an official soap to use, which means its concentration is the same in every bottle, year after year.  This standard soap is made so that one drop will create suds in a test tube of water if that water has less than one grain per gallon.  If the water needs two drops of soap, it should have about 2 grains of hardness, three drops for 3 grains, and so on.  You can get a kit to try this yourself (it's also a fun demonstration for school science projects) from the source listed below.  There are other soap test kits available too - some are listed below as well.  You could even try using a diluted baby shampoo or dish soap to create your own "standard" solution (it's best to dilute with Soft water; to do the tests you'll also need an eye dropper and a container like a small jar with a lid).

There is another simple test called the "Tea Test."  Hardness minerals bind with molecules found in regular tea.  Soft water will make a cup of tea that is the classic orange-brown color, and you can easily see the bottom of the cup.  The flavor of the tea should be crisp.  Hard water will make a suspension of those hardness minerals, which makes the liquid muddy and dulls the flavor.

As a Research Scientist, I have run a series of experiments to investigate claims made by manufacturers of so-called "physical water treatment" devices.  These typically rely on a fixed magnet, an electromagnet, or some unique property given to an ion exchange resin.  Among the many claims for these physical devices is that they give water all the properties of being Soft without actually removing the minerals.  The Soap Test is an easy way for anyone to check out the claim that a device will reduce how much soap is needed.  The Soap Test is considered to be fair because the test is standardized to give consistent results, it is widely available, and is reasonably accurate.  In tis case we just need to see whether the treated water really does behave like Soft water; if it takes more than a drop of the soap solution to create rich suds then the claim is busted.

Test Results


For the Soap Test experiments, I also came up with a way to mix up each test tube in exactly the same way, every time, to be as fair and scientific as possible.  Below is a photo of the results from one test, where Hard water (HW), physically treated water (PWT), and Soft water (SW) are compared.  The hardness of the HW was 20 grains per gallon.  That same Hard water was passed through the physical treatment device to provide the sample used below.  The Soft water was made by passing that Hard water through a standard ion exchange water softener.  Just one drop of soap was added to each test tube, they were shook for 3 seconds, and then the photo on the left was taken.  The softened water made suds, the Hard water and physically treated water did not.  This test shows that folks who have softened water can actually use less soap. 


Recent independent studies on the effects of softened water on appliances, clothing, detergent use, and carbon footprint, are available online.  Those links are listed below as well.

For more information

1. Water Hardness levels:

2. Soap Test Kits:

a. The one I use: 

b. Other kits:

3. Recent independent studies on the effects of softened water


By: Mark B., Senior Research Scientist




Finally, something older than dirt. You won't believe what it is!

by Keith B Published 12.18.2014

We know how important water is to us…but where did it come from? The conclusions of a University of Michigan team, recently published in Science magazine, state that up to 50% of the water now on Earth may have existed before the birth of the sun, 4.5 billion years ago. The article states “water is known to form in the clouds of gas and dust of the interstellar medium (ISM) from which planetary systems coalesce.” So how do we know it's older than the sun? Apparently, the level of deuterium found as a replacement for hydrogen in “heavy water” is the key. The amount of deuterium found in Earth's water, although quite small, is said to be 6 times more prevalent than the “average” level of that element found across the universe. (Please don't ask me how anyone knows that.) Anyway, the enrichment of deuterium only happens in certain conditions. Those conditions are very cold (only ten degrees above absolute zero) plus oxygen and ionizing radiation. All of these are said to be present in the ISM. The theory follows that after the sun was born, the remaining ISM creates a protoplanetary disk spinning around it. The U of M team created models and computer programs that simulated the conditions in that protoplanetary disk, showing that they wouldn't destroy the “heavy water” it came with, but also wouldn't produce much more. Therefore one could conclude that our water, because of its % of heavy water, came from the ISM before the sun was born. All this is somewhat mind-boggling.

Landscape Carina Nebula

While once we thought that water might be somewhat unique to Earth, it is being found in several “new” places. reports that

NASA's Curiosity rover has discovered evidence of a vast lake in Gale Crater that potentially lasted millions of years—findings that may contradict the idea that much of the planet's water reserves were held only in ice or underground, and made only transient appearances on the surface. The new results from studying rocks at the base of Mount Sharp (the 3-mile-high mound in the middle of Gale Crater) points to a lake that filled and drained over tens of millions of years and that could have spanned the 96-mile-wide crater, scientists at Jet Propulsion Laboratory in La Canada Flintridge, Calif., said. And the sediments deposited in this lake could be what helped form Mount Sharp in the first place. ‘The puzzle pieces are coming together,’ Michael Meyer, lead scientist for NASA's Mars Exploration Program, said in a press briefing. The findings from Curiosity, known formally as the Mars Science Laboratory, show that water could have lasted long enough for microbial life potentially to emerge, the scientists said.

Maybe there was life on Mars and maybe someday we will be sending it back.

What is interesting, at least to me, is that once again water shows up at the very beginning of everything and at the center of our lives. We are constantly updated with news that includes floods, droughts, blizzards, monsoons and other water related phenominae. We are developing new and improved ways to produce fresh water from salt water, and to purify and recycle the water we have on the Earth. Many of us are drawn to water; enjoying swimming and boating. We find it relaxing and even rejuvenating to just sit at a beach, or near a lake or stream. Now we think water might just be floating around the universe in giant clouds of gas and dust, making it possible for life to exist potentially on many planets in many solar systems. Amazing!

Contact Keith B.

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Cyanobacteria (aka "Blue Green Algae") and Microcystins

by Mark B Published 8.14.2014

Recently nearly half a million people using Lake Erie for drinking water were warned not to use it. The reason for this is increasingly common in Lake Erie and other surface waters. By the time fall and late summer have rolled around, enough excess nutrients have washed into our waterways that the natural balance can be upset. 

In particular, cyanobacteria – also known as “blue green algae” – are given the ideal opportunity (temperature, sunlight, and nutrients) to outcompete other waterborne organisms to create a vast, green soup that can be dangerous to drink or even bathe in. Harmful algal blooms have also been associated with the death of pets and livestock. In the case of that corner of Lake Erie which serves Toledo and the surrounding communities, toxins called microcystins were found to be present in the water going to people’s homes even after going through the treatment plant. There are many kinds of cyanobacteria that produce at least 80 different microcystins. Other cyanobacteria produce different toxins, such as anatoxins, saxitoxins, and cylindrospermopsin. Microcystins are held in the cell wall of the cyanobacteria, and when the cells break open, the toxins are released. While the US EPA still has no official limit, the World Health Organization recommends just 1 part per billion for microcystins in drinking water. People who consume the water can have rapid liver damage and risk cancer from long term use. Microcystins may also irritate the skin and eyes of people who bathe in just a few parts per billion.
Public water providers are normally very good at dealing with the seasonal challenges of these blooms.  Municipalities at risk test regularly, but this year weather conditions may have conspired to catch them off guard. Recent news reports advise that NASA will now use its satellites to help monitor the lake.

NOAA Great Lakes CoastWatch Lake Erie

NOAA Great Lakes CoastWatch Lake Erie 8-4-2014

It has been found that certain oxidants, such as potassium permanganate (KMnO4), are very useful to not only destroy the cell, but break down the microcystin molecules themselves. In addition, powdered activated carbon may be used since its high surface area and high adsorbency allows it to rapidly soak up the toxins. Microcystins have a molecular weight around 1,000 Daltons, which is probably why reverse osmosis membranes have been shown to be effective. Laboratory testing is critical to ensure that the treatment of any cyanotoxin is effective. 

Although lawns and leaky septic tanks can contribute to this extremely serious problem, there is very strong evidence attributing algal blooms mainly to agricultural fertilizers, perhaps because they are applied at the wrong times or in too great amounts. Life has a natural balance and the cause of harmful algal blooms is preventable. Is it worth getting this extremely important problem under control? Just ask the half million people who spent a few days unable to drink from their faucets, yet live next to the greatest fresh water resource on earth. 

Additional Information:


Contact Mark B.

Water Contaminant: Nitrates

by Mark B Published 6.4.2014
Diagram of a nitrate molecule

Nitrate is the anionic part of a salt that commonly occurs with sodium or potassium. Traditionally it was used in the manufacture of gunpowder and munitions where it was originally extracted from urine and was then mined. Today nitrates are also employed as a source of nitrogen in inorganic fertilizers. Nitrate is limited in drinking water by the US EPA to a maximum of 10 mg/L when measured in units of nitrogen. The particularly susceptible group is infants below the age of six months.This is because the very young digestive tract hasn’t yet matured to handle levels above 10 mg/L, and the amount of water they consume is proportionally higher for their body weight. The infant may be exposed to nitrate when given a bottle of drinking water or reconstituted formula. Nitrate binds to the methemoglobin molecule that carries oxygen in the blood stream, making that oxygen unavailable. As a result, the baby’s skin and lips can turn bluish, the child can appear short of breath, and might be either fussy or listless. The illness is called methemoglobinemia or “blue baby syndrome.” There is as yet insufficient evidence to support an association with drinking water nitrate and birth defects, miscarriage, or harm to adults.

Sources of excess nitrate in drinking water are typically the runoff of agricultural fertilizers or manure and leaching from septic tanks. It is more likely to be found in shallow ground water sources. Municipalities must monitor and treat as necessary to meet the US EPA regulatory limit, therefore private water supplies are normally at greater risk of nitrate contamination. Nitrate in drinking water can be treated effectively by reverse osmosis, distillation, or a tank of nitrate-selective ion exchange resin – expert help is needed to ensure the technology being considered is appropriate for a particular situation. Prevention is an important option. For example, when considering digging a new well, determine whether it will be deep enough and far enough away from feedlot drainage and septic systems to prevent the well water quality from being influenced. Last, because of the potential sources of nitrate, it may be appropriate to test for fecal coliform bacterial contamination as well.

Contact Mark B.

Water Contaminant: Arsenic

by Mark B Published 5.1.2014

Arsenic is a metalloid element that has traditionally been useful in a broad range of applications due to its toxicity. Its occurrence in drinking water is undesirable for the same reason. Arsenic in groundwater is typically associated with deposits found in geologic formations. Leached into drinking water, it has been associated with a wide range of health effects that include lower intelligence in children, cancers, keratosis, and endocrine disruption. Arsenic can cross the placental membrane to reach the fetus. In 2001 the US EPA set the regulatory limit in public water supplies at 10 μg/L, although hundreds of small water systems remain out of compliance. The World Health Organization and Health Canada both have a Guideline value of 10 μg/L.

Inorganic arsenic is currently considered to be of greater concern to human health than the organic forms. Inorganic arsenic may be in the form of either trivalent arsenite or pentavalent arsenate. The former is more toxic and more challenging to remove due to the low proportion of ionic charge at drinking water pH. Arsenite is easily oxidized to arsenate with sodium hypochlorite, gaseous chlorine, permanganate, and ozone. It is less readily oxidized by chloramination, chlorine dioxide, contact with air, and either 254 nm UV light or hydrogen peroxide by themselves.

Periodic table cell for Arsenic

Arsenic can be treated at the household level whether the water is from the municipality or from a domestic source. It first needs to be measured for concentration and ideally, arsenic species, so that an appropriate treatment can be provided. Test kits are available that can be used, with some practice, to determine concentration of total arsenic. Speciation is probably best performed on site by a professional prior to submission to a laboratory for analysis.

It is unclear whether arsenic enters the body only by consuming it or by transdermal means as well. To treat the whole house (point-of-entry, or POE), a number of granular adsorbent media are available with varying effectiveness depending on species, pH, and interfering ions in the water. Some media claim to be effective on both arsenite and arsenate, though they may be more expensive. Often a low cost media, such as an iron-doped activated alumina, can be used economically in conjunction with a hypochlorite feed. A lead-lag tank system is often employed to allow monitoring of the beds as they deplete and thereby facilitate bed replacement prior to breakthrough. Depending on available space and the amount of naturally occurring iron consistently found in the source water, another practical POE alternative may be to oxidize both iron and arsenic, then filter out the co-precipitated floc with a bed of backwashable media. A rule of thumb is that a minimum ratio of 20:1 iron to arsenic is needed to consider this option. Reverse osmosis and distillation may be used for point-of-use (POU) applications. Higher arsenic concentrations can potentially be addressed with a post-membrane polishing cartridge for POU reverse osmosis. Ideally, systems being considered will be certified to ANSI/NSF Standards 53, 58, or 62 for arsenic reduction, or proven by some other third-party means such as the EPA’s programs for Environmental Technology Verification or Arsenic Demonstration. Regardless, regular monitoring is an important facet to any process for the reduction of arsenic in drinking water.

This is a contaminant which requires professional involvement for assessment, treatment, and maintenance to assure long term effectiveness.

Contact Mark B.

What is hard water, and how does hardness affect my home?

by Cathy J Published 10.15.2013

Most homes have hard water, whether it is supplied by a private well or a municipality. Although hard water is comprised of naturally occurring minerals and is not known to be harmful to humans or animals, it has the potential to cause damage to skin, hair, water using appliances and plumbing.

Pure water is the universal solvent. It is tasteless, odorless and colorless but as it makes its way through soil and rock, it dissolves minerals and holds them in solution.  The two most common minerals that make water hard are calcium (Ca) and magnesium (Mg). The higher the calcium and magnesium content of the water, the higher the hardness level.

Hardness is measured in grains per gallon (gpg). Water with a range of 1.0–3.5 gpg is slightly hard. Conversely, water that is more than 10.5 gpg is classified as very hard. However, even small amounts of hardness in a water supply can be detrimental.

Water Hardness Scale (grains per gallon)
Less than 1Soft
1.0–3.5Slightly Hard
3.5–7.0Moderately Hard
Greater than 10.5Very Hard

A white film or spots on shower doors, glassware or fixtures may indicate hardness. The film may also be left on skin and hair after bathing, resulting in dryness and the use of extra hair products and lotions. Additionally, hard water can leave mineral deposits in pipes and water using appliances. This is apparent when the flow of water is decreased or when appliances become inefficient or need multiple repairs. According to the Water Quality Association, a consumer's water heating costs could increase as a result of hard water. When hard water is heated, the minerals can precipitate and form scale. This scale build-up forms an insulating barrier between the heating element and the water to heated.

Hardness also has an effect on soaps and detergents. The cleaning properties of detergents and the amount of suds produced are diminished. Calcium and magnesium ions actually react with soaps and detergents to create “soap curd”, sometimes called “soap scum”. Soap curd reduces the life of clothing and makes them look gray or faded.

Hard water is treated several ways. The most common household method involves ion exchange which occurs when the positively charged calcium and magnesium ions are exchanged for sodium ions in a water softener. This process is explained in more detail in the video, How a Water Softener Works. One disadvantage of ion exchange is that sodium is introduced into the water supply. Consumers on a sodium restricted diet need to count this as part of their daily intake if drinking softened water.

Water may also be softened with chemical precipitation. This process involves imparting lime in the water supply to raise the pH. When the pH level is high enough some hardness compounds will precipitate and can be filtered out. With chemical precipitation, the amount of hardness in the water will be reduced but not completely removed. The water may also be cloudy and the precipitate can cause build up.

Silica in the Water Supply

by Cathy J Published 5.30.2013

A common concern among homeowners is the appearance of a white film on water using appliances and fixtures and etching of glassware. Most often, the culprit is calcium and magnesium, otherwise known as hardness, which can easily be treated with ion exchange. But in some cases, even with this type of treatment, the film and etching problems persist. It could be silica.

Silicon dioxide or silica (SiO2) is an oxide of the element silicon which is the second most abundant element found on earth. Silica is present in all natural water supplies in some form. Additionally, many foods such as, strawberries, avocados, onions, root vegetables, wheat and oats contain silica. And, it can found in nature as sand, sandstone, quartz, flint, agate or granite. Being a hard, glassy substance on its own, silica is commonly used to make glass. Windows, bottles, glassware and even optical fibers for telecommunications are all products of silica as are some ceramics, abrasives and concrete. Some studies indicate that silica has health benefits. It is needed for bone, cartilage, hair and nail growth and is an ingredient in many multi-vitamins and dietary supplements. Other studies show the contrary, however; silica has no nutritional value. In either case, it does not appear that silica is harmful to the human body if ingested in small quantities and is unregulated by the EPA.

Water among other things that contain silica, such as onions and sand

In a water supply, silica can exist in a dissolved, particulate or colloidal form. A colloid is a very fine suspended particle which does not settle readily. In high enough concentrations, silica has a tendency to form scale deposits. This is especially true in high temperature boiler applications and in the power generation field where silica can deposit on turbine heads.

Treatment for silica depends on the form it’s in. In the particulate form, silica can be removed by simple filtration. The colloidal form may require chemical addition such as magnesium salts followed by filtration or reverse osmosis (RO). In the dissolved form, RO and anion exchange work well, however anion exchange is not generally practiced in domestic applications as it requires caustic soda to strip the silica back off. Needless to say, silica removal is not as easy as it appears.

If you suspect that silica is present in your household water supply, it is always best to contact a water professional for an evaluation. An easy way to test if scaling might be silica is to wipe the affected area with white vinegar. If the vinegar removes the scale or film, it is most likely hardness causing the problem. If the vinegar does not clean the scale or film, it could be silica.

Contact Cathy J.

Hydrogen Sulfide in Well Water

by Cathy J Published 10.20.2012

“My water smells like rotten eggs.” This is a very common complaint from many homeowners but one that may be easily explained. Hydrogen sulfide, a compound that is widely known for its distinct rotten egg or sulfur odor could be the culprit. This colorless, flammable gas occurs naturally in gases from swamps and stagnant pools of water, volcanoes, hot springs or crude petroleum. H2S is also a waste product of many industrial processes and from municpal sewers and sewage treatment plants. The production of H2S is due to a process called anaerobic digestion, a breakdown of organic matter in the absence of oxygen.  A shower spraying rotten eggs into a bathtub

In well water supplies, H2S is commonly formed by sulfate reducing bacteria. Well water naturally contains minerals of sulfate picked up from soil and rock formations. Sulfur reducing bacteria can change sulfates in the water to hydrogen sulfide gas. In other cases, hydrogen sulfide in well water can be caused simply by the decay of organic matter.

The human sense of smell can detect H2S in concentrations as low as 0.5 ppb (parts per billion). In addition to the odor, the taste of the water may also be affected. If left untreated, H2S can corrode steel, stainless steel and copper pipes. It can also tarnish silver and leave yellow or black stains on bathroom fixtures. While the amount of H2S typically found in most household water supplies is not high enough to pose serious health risks, slight nausea can occur due to the foul odor.

There are several options to treat H2S in a water supply. Trace amounts of the gas can be handled by activated carbon. If you have low to moderate amounts of H2S in your water, the gas can be converted to elemental sulfur and then filtered out by using an oxidizing filter. High amounts of H2S may require more advanced treatment.

It is important to note, if the rotten egg smell is only present in the hot water, not in the cold water, chances are the problem lies in the hot water heater. All hot water tanks have an anode rod, which is in place to prevent corrosion of the tank. However, if anaerobic bacteria are present in the water, they can use the electrons produced by the corrosion of the anode rod as an energy source to produce H2S. One simple fix is to switch out the anode rod in the tank. Check with a reputable dealer for replacement anode types to ensure you keep the warranty intact. Turning the temperature up on the hot water tank for a short period of time to kill the bacteria may help. But, remember to turn the temperature back down and drain the tank, otherwise scalding may occur. Shock chlorination of a private well is a temporary solution as well. Although these fixes can reduce the odor problem, they aren’t permanent.

If you suspect you have H2S in your water, it is best to contact a water professional for further on-site testing and precise treatment solutions.

Contact Cathy J.

Why are boil water alerts so important?

by Cathy J Published 6.8.2012

A boil water alert (BWA) is issued when there is a threat of disease causing microorganisms such as Giardia lamblia and Cryptosporidium eDrinking Cautionntering a water system. Contamination can be caused by several different factors, most commonly due to water main breaks or severe flooding which might allow the possibility of foreign substances to enter the water system.  In less common instances a BWA can be issued when there is a significant change in the turbidity reading. A BWA is issued after careful consideration among representatives from public health, regulatory agencies and municipal departments. 

When there is a BWA, it will be broadcast on the local news (radio, television, web) with instructions on what to do and how long it will last. 

The best way to make sure your water is safe for drinking, cooking or brushing your teeth is to boil your water.  To effectively kill the disease causing organisms, boil the water for at least one to five minutes.  Allow water to cool before use.  The water will taste “flat” but will be safe to use.  If you are unable to boil your water, you can use bleach or iodine.  Bleach will kill some, but not all, types of disease-causing organisms that may be in the water.  Add 1/8 teaspoon of regular, unscented, liquid household bleach for each gallon of water, stir it well and let it stand for 30 minutes before you use it. Store disinfected or boiled water in clean, air-tight containers with covers in the refrigerator. 

Hot (not boiled) soapy water will be sufficient for dishwashing and surface cleaning.  As a precaution, add one tablespoon of bleach per gallon. Unless specifically list in the BWA, laundry water and water for showering does not need to be treated.

Boil alerts are mostly for city and community water supplies.  If you have a well, you would want to boil your water after severe flooding or if your well pressure drops to almost non-existent (indicating a potential problem).  After correcting the problem or when the water recedes, it is recommended that you have your water tested by your local EPA certified laboratory to make sure it is safe to drink.

For a list of local certified laboratories or more information on safe drinking water, a very informative, reliable source is the EPA. 


Contact Cathy J.

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