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Hard Water vs Soft Water Explained: What’s the Difference?

hard water vs soft water

Water is the basic, most important component to life.

Humans cannot survive without drinking it, and our biological makeup is mostly water itself. Along with drinking, water is vital for daily activities like cleaning and crop irrigation.

This being the case, water is also one of the largest unifying factors in the world, but possibly a subject that many people don’t know a lot of details about- surprising seeing as it is the most common element we use.

Understanding the properties of your water, such as its source, its makeup, and its hardness or softness is vital when it comes to being conservation minded and conscious of your usage.

The difference between hard water and soft water

We often hear people say things like:

“oh they must have hard water because they still have spots on their glasses”


“this shower must use soft water because look at how much my shampoo is lathering”.

At first assumptions, we might think that soft water is inherently better, possibly by virtue of name alone. But when looking at the properties of both hard and soft water, their respective advantages and disadvantages, we get a complex picture.

This article will work through these properties of both hard and soft water, as well as how to identify which water is being used in your home or business, and will compare the two types, presenting arguments for both hard and soft water. By the end, you’ll have all the information you need to feel well informed and confident in your water quality!

So, before we get into any of the details, what really is the difference between hard water vs soft water?

What is hard water?

Put simply, the hardness of water is determined by the amount of dissolved minerals like calcium and magnesium contained in the water itself.

The higher the content of these minerals, the harder the water.

These minerals are acquired when water runs over rocks or surfaces where calcium and magnesium are present, such as limestone, gypsum, or chalk, and the water picks up the ions as it flows.

Some people prefer hard water as drinking water, because there are benefits to the ingestion of the minerals, but when it comes to household chores hard water is more of a hassle to use.

The hardness of water is measured and calculated in grains of hardness per gallon of water, or as parts per million or milligrams per liter. The chart below shows this breakdown of water hardness categories from soft to very hard. Water hardness is reported to be a problem for daily use when the hardness reaches and exceeds the 6-7 grains per-gallon level.

There are two different types of water hardness though, as subcategories unto themselves apart from their simple hardness rating: temporary hardness and permanent hardness.


Temporary Hardness

Temporary water hardness is caused by dissolved bicarbonate minerals, like calcium bicarbonate and magnesium bicarbonate. These minerals can be boiled out or removed by lime softening and ion exchange softening.

Boiling the water to remove the minerals allows carbonates to form from the original bicarbonates, and removes the calcium carbonate from the water itself.

Lime softening is a treatment that adds limewater, or calcium hydroxide to remove the calcium and magnesium ions by precipitation.

Permanent Hardness

Permanent hardness can be treated by ion exchange treatment, a process where sodium ions are injected to replace the magnesium and calcium ions.

We’ll get into more water softening processes below, but these are two common methods.

What is soft water?

Water in its ‘pure’ form though, as fresh rainwater, is naturally soft. It is the journey the water takes once it reaches the ground that changes its structure.

To return hard water to its soft water state, water softening systems are employed to reduce the concentrations of minerals, leaving a higher concentration of sodium in the water, but with significantly less magnesium and calcium. Because of the higher sodium content, people sometimes don’t like to drink soft water, as they say it tastes ‘salty.’

However, the lack of mineral deposits in the water makes things like washing dishes, cleaning your shower head, and washing clothes a lot easier as soft water doesn’t leave soap scum or mineral stains.

Let’s take a closer look at the individual properties of hard and soft water, indulging in the chemistry side of things before diving into the advantages, disadvantages, and treatments.

Hard Water: Chemical Makeup and Ion Components

As stated above, hard water is water that has a high mineral content in comparison to soft water.

Calcium, magnesium, and iron are all common mineral ions in hard water.

Since these are all minerals that humans ingest and come into contact with regularly, there is no danger to hard water and using it as drinking water. In fact, some people prefer hard water as a way to increase their magnesium and calcium intake levels. While it’s easy to just say ‘hard water’ and call it a day, it’s important to look behind that term and present the chemical makeup of the water.

The calcium and magnesium present in hard water are usually in the form of bicarbonates, chlorides, and sulfates. Bicarbonates are a polyatomic anion, serving in the pH buffering system. In the human digestive system, bicarbonates work to raise the pH of the stomach after highly acidic digestive juices have been processed and also regulates the pH of the small intestine.

Magnesium bicarbonate, the kind found in hard water, can only be found in aqueous solutions and does not form a solid. Similarly, calcium bicarbonate does not exist in a solid, being formed purely in aqueous solutions.

Chlorides are an ion most commonly found in sodium chloride, magnesium chloride, and potassium chloride. Like with a magnesium bicarbonate, magnesium chloride can contribute to hard water buildup in pipes and faucets.

hard vs soft water
(Credit: Wikimedia, Creative Commons License)

Sulfates can be found in almost all natural water, and is one of the major dissolved components of rain. When combined with calcium and magnesium, a high concentration of sulfates can lead to a laxative effect. Sulfates enter water from rocks and soils containing sulfate minerals, in the same way that magnesium and calcium are acquired.

Other contributing elements to hard water are dissolved metals like aluminum, barium, strontium, iron, zinc, and manganese. When present in divalent cations, or ions with positive charges with a valence of 2+, tend to combine with anions present in the water to form stable salts.

The specific anion that is found in these salts relates to the carbonate hardness. Carbonate hardness, then, is the result of metals combining to form alkalinity, the capacity of water to neutralize acids.

The presence, then, of these metals and carbonate hardness leads to an increase in temporary water hardness itself, as it can be removed by boiling water. The following compounds form carbonate hardness: calcium carbonate, magnesium carbonate, calcium bicarbonate, magnesium bicarbonate, calcium hydroxide, and magnesium hydroxide.

The dissolved salts such as magnesium, calcium, and iron present in hard water become insoluble deposits when the water flows through something like a faucet. The water evaporates or leaves the surface, while the minerals stay behind, producing build up on things like shower heads or scale in boilers.

To soften waters with these components, boiling water, ion exchange, or other treatments must be performed.

Soft Water: Chemical Makeup and Ion Components

When looking at the chemical makeup of soft water, it is best understood in comparison to hard water.

The absence of all the high mineral content in hard water equals soft water.

When water falls in the form of rain, it has already been precipitated into the atmosphere and hence purified of any minerals that it had on the ground, hence falling back to earth in a ‘pure’ state.

Soft water is free from dissolved salts, and thus does not leave behind hard buildup. However, soft water does not always have to be completely void of these ions, they are just present in low amounts.

Hard vs Soft Water – Geographic Themes

Since water hardness is the result of aspects of the nearby terrain, the levels of water hardness are geographically reliant. In the United States, there are four main categories of water hardness: very soft, soft, hard, and very hard.

At least 85% of US households have reported hard water levels from slightly hard to extremely hard.

Very soft water states are concentrated in the southeast, the northeast, and the pacific northwest. The water in these areas shows a very low concentration of magnesium and calcium, between 0 and 60 milligrams per liter of calcium carbonate.

Moderately soft water states, or just soft states appear to be quite random, with regions of Hawaii, Alaska, North Dakota, Minnesota, Missouri, Tennessee, West Virginia, and Pennsylvania included. The milligrams per liter in these regions measure between 61 and 120 parts per million.

Hard water regions are found in Illinois, Nevada, Idaho, Montana, Kansas, Oklahoma, Texas, Michigan, Kentucky, and Ohio. These moderately hard regions are throughout the eastern-central midwest, and the towards California. They measure between 121 and 180 milligrams per liter in parts per million for calcium carbonate.

Very hard water states, measuring between 181 and 250 of calcium carbonate in milligrams per liter, are found very solidly in the midwest and along the US-Mexico border, as well as sprinkled throughout Ohio, Illinois, and New York, and Florida. These regions almost always have to implement a water softening system in order to remove the negative impact of hard water.

The map below can give you a clear idea of where your water might fall based on your region:

Water Hardness Map
Source: usgs.gov

Effects of Hard Water

Now understanding what qualifies water as hard or soft based on the chemical makeup and how it comes to be so, it’s a good point to discuss the physical effects of hard water on people and surfaces on which its used, both good and bad.

Benefits of Hard Water

  • Full of minerals essential for good bodily function
  • Safe to drink and often tastes better
  • Reduces risk of kidney stones & hypertension
  • Magnesium can help prevent heart disease

Hard water can be seen as preferable as drinking water to soft water. This is due to the fact that mineral content in hard water provides nutritional value that humans need.

As calcium and magnesium are two essential minerals to humans, their presence is a desirable benefit of drinking hard water. Not getting enough of either mineral and lead to increased risk of osteoporosis, kidney stones, hypertension, and a number of other conditions and diseases.

Calcium in hard water is particularly significant because an inadequate amount of calcium in the body can lead to an increase of fracture risk and a decrease in joint health. An excess of calcium in the human body is generally protected by a natural intestinal absorption regulation, and so does not pose a large risk.

Magnesium is related to an increased function of the energy metabolism, protein and nucleic acid synthesis, and plays an active role in at least 350 cellular enzymes, making it a significant mineral in bodily functions. Low levels of magnesium are associated with blood vessel problems and insulin issues. It has also been connected to hypertension, coronary heart disease, and type- 2 diabetes mellitus and metabolic syndrome.

Hypermagnesemia is the condition of an excessive presence of magnesium in the body. When magnesium is present in water with sodium, as hard water is, at high concentrations, it can sometimes present a  laxative effect on the body. However, data has shown that people adapt to these levels and the side effect subsides.

Both magnesium and calcium in hard water pose more positive health effects than negative. Their levels being relatively low do not pose significant risk nor life-changing benefits, and so the ingestion of hard water generally boils down to the more favorable taste.

Of course, taste preference is left up to the individual, but the addition of minerals to water is a common practice that even bottled water manufacturers participate in.

Disadvantages of Hard Water

  • Limescale buildup on appliances
  • Clothes don’t get fully clean
  • Water spots left on dishes and faucets
  • Can cause appliances to be less efficient
  • Soap scum buildup in showers and bathtubs
  • Exacerbates eczema symptoms and dry skin

Recent studies have linked the exposure of hard water with an increased presence of eczema, the hard water acting as an inflammatory risk factor to the condition. This connection is unsurprising as eczema is closely impacted by environmental factors ranging from dust to diet to shampoo and sweating.

Apart from the health effects, perhaps the most obvious results of hard water are seen in household chores.

Hard water causes an increase in soap use, since the high levels of minerals do not allow for lathering. This leads to the undesirable byproduct of soap waste, and some people feel like their shampoo is never doing the whole job, leaving hair feeling a little sticky and looking dull.

This also plays a part in the hard water used in washing machines, where over time the cleaning agents do not fully remove the soil, leaving garments looking dingy and even feeling harsh and scratchy.

Hard water used for dishwashing is easy to spot when the dishes dry, with dishes having a film left on them and spots on things like wine glasses.

This same film can be felt on bathtubs, sinks, and shower doors, in addition to soap scum, a hard to eliminate spotting on sinks, showers, bathtubs, and appliances when soap combines with the dissolved calcium and magnesium left behind by flowing hard water.

One of the more frustrating side effects of hard water is the limescale buildup. When calcium carbonate and magnesium carbonate are heated and precipitate from the water, they form a mineral deposit at the bottom of the water heater, reducing the efficiency and service life of the unit.

Not only does this decrease the efficiency of your water heater, but a large mineral deposit will lead to a shorter lifespan of your water heater.

These deposits also accumulate on shower heads, faucets, and coffee pots, decreasing water pressure and efficiency just the same as the heater. Therefore, a lot of times when water-using appliance cuts out before its time and you can’t see any physical malfunctions, the answer is likely to be the presence of hard water and buildup of mineral deposits.

How do you clean and remove these calcium deposits on shower heads and faucets?

The DIY solution is to fill a small plastic bag half full with white vinegar and attach it to the shower head, leaving the bag in place for a few hours. Once you remove the bag, take a toothbrush and scrub the shower head. The vinegar will have made the buildup easier to remove and you should be able to seamlessly scrub off the deposits, restoring your shower head.

hard water stains

Effects of Soft Water

Soft water is of course the antithesis of hard water, right down to the benefits and drawbacks. Where hard water poses advantages, soft water is less preferable. Where hard water makes household chores and cleaning more difficult, soft water produces less damage on material.

Benefits of Soft Water

  • Increased efficiency of appliances
  • Moisturized hair and skin
  • Cleans clothes more thoroughly
  • No residue buildup in sinks, bathtubs or showers
  • Spotless, clean dishes

In contrast to hard water leaving films and skin and hair feeling sticky or heavy, soft water has a moisturizing effect on the skin and hair. The soft water promotes the lathering agents in soap, and improves rinsing efficiency.

Soft water helps humidify the skin and hair, which is especially useful in dry winter months. At the least, soft water does not detract or hinder skin and hair health.

Similarly, using soft water to wash clothes and dishes allows the water to dry without leaving water spots and does not promote discoloration of clothes in the wash because it does not leave a mineral residue.

However, the most prominent effect of soft water is that, unlike hard water, it doesn’t slow down and shorten the lives of your appliances.

Since soft water does not leave a trail of mineral residue, your pipes, appliances, and water heaters are not at risk of limescale build up. Soft water, then, saves you money on cleaning supplies and appliance repairs, means less cleaning of water stains or rewashing of clothes, and smoother skin and hair.

Disadvantages of Soft Water

Because of the lack of minerals in soft water that give hard water a slightly different taste, sodium is the sometimes noted taste in soft water. This is due to the process of softening water, where sodium is added to remove the hard elements like calcium and magnesium.

This taste usually isn’t significant though, and again it’s left up to the individual to decide which they like better. Most at home water softeners will not leave a salt taste in your water, nor is soft water “salt water.”

hard water vs soft water comparison chart

How to Test for Water Hardness

Visual Test

After understanding what hard water is and what some of the effects are you now have an idea of how you can begin to test if you have hard water.

You may have already noticed your faucets or dishes continuously have water spots on them, a keen indication of hard water. Along those same lines, you might be experiencing scum buildup in your bathtub or shower.

However, it is not always that easy or obvious to tell if you have hard water, especially if you live in a moderately soft or moderately hard water area.

As hard water is measured by “grains” per gallon, in milligrams of calcium per liter, or parts per million, it might take a bit of math to determine your exact hardness. Water test labs perform this, but there are at home and simple ways for you to measure it yourself.

DIY Bottle Test

The soap test is the most popular and DIY option to test your water hardness.

All you need is a small glass bottle with a tight cap, dish soap, and any measuring device like a measuring cup or 12 ounce drinking cup:

  1. Fill the bottle one third of the way full and add a few drops of liquid soap (that lacks detergent, something like Castile works),
  2. Shake the bottle for a few seconds.

A lack of foamy bubbles and a cloudy appearance of the water suggests hard water. Soft water would produce a significant amount of bubbles and the resting water in the bottle would be clear.

Of course, this  is a crude method of testing.

At home water testing kits include test strips and color charts.

At Home Test Kits

For These tests, you generally fill a cup with water from a bathroom rink, insert the test strip, and compare the color of the strip with the chart. These tests are available at major stores like Lowe’s, Walmart, and Home Depot, as well as online on Amazon

These tests are cheap and easy to perform, and produce results accurately.

Municipality Reports

Of course, you can also call your city and see what type of water your home is using, as this information is readily available. Households on well-water, though, will need to do their own testing to get an accurate picture of their sources.

Knowing the specific level of hardness of your water can better inform your decision on how to go forward.

Hard Water Solutions – How to Deal With It?

The first reaction to unwanted hard water is “great, well how do we fix it?”

Water softeners are conditioning systems that turn hard water to soft water using various methods. Luckily, there are several options for water softening which we’ve outlined below.

Water Softener Systems

Water softeners have been developed to help alleviate the problems caused by hard water. These types of water conditioners work by passing water through what is called a resin bed in order to exchange the the hard water mineral ions, resulting in soft water. There are a few different types of water softeners available:

  • Salt based water softeners
  • Salt-free water softeners
  • Electronic descalers

Single Tank Water Softeners

A type of salt based water softening system and as the name suggests, a single tank water softener has one resin tank and one brine tank, the resin tank containing the resin beads to remove the hard water minerals, and the brine tank storing the salt.

With single tank water softeners, you have a limit for how many gallons of water you use, regenerating in the middle of the night. While the tank regenerates, no soft water is available. Another drawback of the single tank water softener is that it uses hard water to clean itself, leading to an increase in the very limescale buildup you are working to eliminate within your house.

Dual Tank Water Softeners

A dual tank water softener has two resin tanks and one brine tank. Obviously, the advantage to the dual tank system is that when one tank reaches its soft water capacity, the system automatically switches to the reserves in the second tank, not signalling a delayed regeneration period like single tank systems.

Of course, both systems have their benefits, with a single tank costing less and taking up less space, but the dual tank produces the highest level of efficiency and a higher water quality.

Electronic Descalers

The Ion exchange resin method is one we’ve already touched on, where the calcium bicarbonate and magnesium bicarbonate are replaced with sodium or potassium ions.

In this process, the electric charge of magnesium and calcium allow for like charges to repel one another and opposite charges to attract. The ion exchange itself takes place as the calcium and magnesium make contact with negatively charged man-made resin beads and displace the sodium ions.

Resin beads are a sticky, insoluble substance that’s coated with positively charged sodium ions. The displaced sodium ions then pass through the resin ‘bed’ and out of the softener outlet, leaving the magnesium and calcium still connected to the resin ions dislodged from the water, thus producing soft water.

Template Assisted Crystallization (TAC)

Another salt-free water softening process is something called Template Assisted Crystallization, or TAC. The hardness minerals in hard water are converted to a crystal that is not able to bind to surfaces.

While this is actually a process of water conditioning, not softening, the results are comparable seeing as the minerals and impurities are still strained out from the water source.

Wrapping Up

Overall, the comparison and elements of hard water and soft water are complex. Both types propose significant benefits to the consumer, but both also have drawbacks.

It is a general consensus, though, that soft water is typically preferred for residential households and businesses alike.

While water softening systems cost money upfront, their installation can save you thousands in repairs and replacements of appliances down the road, not to mention the soft water contributing to the extended life of your clothes, an increased health of your skin and hair, and the lack of waste in cleaning products.