How Do Water Softeners Work?


If you live in an area with hard water, then you will be all too familiar with the problems that it can cause. If you're not overly familiar with the differences between 'hard water' and 'soft water', consider yourself lucky!

Hard water is the term that is used to describe water that has a lot of calcium, magnesium, and other minerals in it. These minerals, in the quantities found even in hard drinking water, are not dangerous, but they can cause problems for your plumbing. For this reason, a lot of people choose to invest in water softeners. You may be wondering, should you buy a water softening system? How do those systems work, anyway? What technology is available, and is there a difference between the most common systems on the market? We're here to answer those questions, and more, in this simple guide to water softeners.


Hard vs Soft Water

Water that contains a low concentration of minerals is soft. Water that contains a higher concentration is, as described earlier, hard. In some areas of the country, water is naturally soft because the water supply comes from fresh lakes or streams. Some water is treated by the municipal water companies to make it soft. In other areas, however, the water comes from underground sources, and that underground water picks up minerals from the rocks that it passes through. Areas with a lot of chalk, gypsum or limestone will likely have groundwater reservoirs with hard water.


Why Does Hard Water Matter?

Drinking hard water that is otherwise potable is not dangerous. There are no known health concerns relating to drinking water with calcium or magnesium in it. Small quantities of those minerals are actually beneficial for our health and wellbeing.


The problem is that the water can damage your appliances by clogging pipes or building up on heating elements. You may have seen a white, flaky residue, known as 'scale' building up around the outside of your taps or on the heating element of your kettle. If you have, then this is a sign that you live in a hard water area. Similar residue could be building up inside your pipes and in your heating system. If the scale gets too bad, then it could damage your heating or plumbing.


That's not the only issue with hard water. If you have hard water, then bubble bath may not produce a lot of bubbles, soap might not lather very well, and you may find that you have to use a lot of washing powder or liquid too. In addition, if your skin is sensitive to the minerals you might find that you feel a little itchy after showering. Even if you aren't sensitive to the minerals, some shower gels and soap might produce a 'scum' when they bind to the minerals in the water, leaving marks around the edge of your bath or shower that you need to wash away.


How Water Softeners Can Help

In an ideal world, the municipal water company would provide you with soft water. This is not always possible, however. If the water coming through your mains pipes is hard, then you will need to find ways to soften it. Some people simply opt to soften the water that comes out of their kitchen taps, using a water filter for that tap only. This is OK if all you want is soft water for drinking and cooking, but it does not solve the issue of hard water potentially damaging your heating.


There are other water softeners that can be fitted to your tank, and that will treat all of the water that passes through the house, removing the minerals and producing water that does not leave scale on your pipes and heating elements.


How Do Water Softeners Work?

Water softeners filter water to remove the magnesium, calcium, and other minerals. There are a few different ways that this can be achieved. The most common types of water softener are:

Salt-Free Water Softeners:

These are basic water softeners that remove calcium using a mechanical filter. They do not remove magnesium, and this means that they are not suitable for people who live in areas with very hard water. They are, however, cheap to install.


Ion Exchange: 

The most commonly used water softener for domestic purposes is the ion exchange system. This filters out calcium and magnesium ions, and replaces them with sodium. 


Reverse Osmosis: 

You may have learned about osmosis in your high school biology classes. Reverse osmosis filters remove impurities from water, not just calcium and magnesium but other impurities too. While this system is effective, it is also expensive and requires a lot of water to work fully.


Let's take a look at ion exchangers in more detail:


A Breakdown of Ion Exchange Systems

Ion exchange systems remove the calcium and magnesium ions in your water supply and replace them with potassium or sodium ions, which are soft. This exchange takes place inside a resin tank. When water flows through the tank of the water softener, it will come into contact with the salt ions that have been added to the resin beads in the tank.

These systems contain three parts:

  1. The Mineral Tank
  2. The Brine Tank
  3. The Control Valve

The mineral tank contains the resin, and is what 'filters' the water. Meanwhile, the brine tank holds water that is saturated with salts, and that is used to backwash the mineral tank that filters your household water, 'recharging' the resin. This process is managed by the control valve and regulator, either on a timer or based on the amount of usage.


This filtration process makes the water softer, but the tradeoff is that the water becomes slightly more salty. The difference should not be enough that you can taste it, but there will be more potassium and sodium in 'softened' water than there is in most naturally soft groundwater.


One problem with these systems is that they require the beads in the resin to be coated with salt so that there are salt ions present for the ion exchange to take place. As water passes through the system, the salt ions become depleted, leaving nothing but magnesium and calcium ions. The system needs to be recharged by adding bags of salt to the softener's brine tank. This causes a form of 'reverse ion exchange' with the hardness magnesium and calcium ions swapping places with the salt in the brine. The hard water can then be flushed away as wastewater.


The most common type of ion exchange water softener that you will find in domestic properties is called Demand Initiated Regeneration water softeners. This means that the water use is metered, and that the regeneration process only takes place when it is required. Older systems did not meter water usage, and instead would regenerate on a timer. This was sometimes wasteful, especially for households that did not use a lot of water. It also ran the risk of people running out of soft water if they changed their usage habits and started using a lot more water for a time.


Ion exchange systems can use one of three different types of salt: rock salt, solar salt, or evaporated salt.

The cheapest type of salt is rock salt. This salt contains more insoluble materials than other types of salt, however, so it is not always the best choice for a water softener. Solar salt is salt that comes from evaporated seawater and evaporated salt is refined, purified salt that is often used as table salt. Solar and evaporated salts are better for producing clean, soft water.


If your water softener regenerates a lot because you use a lot of water, then you should look at getting solar salt or evaporated salt for your water softening system. This will help to avoid the risk of a build-up of non-soluble minerals in your brine tank. There will still be a small amount of excess mineral contamination, even with those salts, but the excess should get rinsed away during the regeneration process.


Some people opt to use potassium chloride instead of sodium chloride because they do not want to take in extra sodium via their drinking water. Potassium chloride costs more than standard salts for water softening and is not compatible with all water softeners, but most modern systems can accept it. If you are thinking of purchasing potassium chloride to use in your water softener, you should seek advice from the manufacturer first.


The Pros and Cons of Ion Exchange Water Softeners

Given everything that we have said so far, you could be forgiven for thinking that if you have hard water, you need to soften it, and that there is no other option. If your water is very hard, then it's true that there are benefits to softening it, however, it's not quite that simple. Let's take a look at the advantages and disadvantages of using a water softener.


Why use a water softener:

  • Softening your water reduces or even eliminates the build-up of scale inside your pipes and appliances, and on dishes. This makes cleaning easier and may help the appliances last longer.
  • Soft water allows soap and detergents to lather better, making them more effective at cleaning
  • Some people find that hard water irritates their skin, so showering or bathing in soft water is better for them.


Why avoid water softeners

Do You Really Need Water Softeners?

If you believe the marketing hype, everyone should have water softeners. This isn't necessarily the case, though. Water softeners are not necessary for all homeowners. You only really need one if your water hardness is greater than 7ppg, or 120mg/l.


This means that less than half of all U.S. homes require a water softener. Even if you do live somewhere that has hard groundwater, that doesn't mean the water that reaches your home will be hard. A lot of the time, the municipal water companies treat the water supply to make it suitable for home use.


Some people with treated hard water, or with water that has a hardness level just under 7ppg, opt to treat it anyway. There's certainly nothing wrong with doing this. Treating your water to make it very soft is not dangerous or the wrong thing to do. Before you opt to spend money on water softeners, however, you should think about why. Do you actually experience any negative effects from hard water? Do you have the money and time to invest in a water softener and the maintenance required? If you are lucky enough to be able to afford a water softener, then that is up to you, but make sure that you're investing in one for the right reasons, rather than just marketing hype.


Before investing in a water softener, you should consider the plumbing system that you have, and seek professional advice. Ion exchange water softeners release salty water into the sewerage system, so make sure that your sewerage system can cope with it. If you have a septic tank, then you should definitely seek advice to make sure that the saltwater will not cause issues.


Water softeners are not a panacea. They reduce scale and can solve problems with bubble bath not producing bubbles and soap not producing suds, but they do not solve issues with water that smells or that contains ferrous iron. So, if you are encountering a rotten-egg smell from hydrogen sulfide, or seeing rust marks or black stains in your sink, you should call the municipal water company or look for a water treatment system that can cope with iron, hydrogen sulfide, or manganese. Ion exchange water softeners won't help you with those problems.


If you cannot use an ion exchange water softener, you may have the option of using one of the other systems instead. The other systems, in general, cost more to run, but produce water that has less sodium in it, and are often better for the environment in other ways.


Alternatives to Water Softeners

There are some viable alternatives for treating hard water, although a lot of them don't actually soften the water at all. Rather, they address the problems that hard water causes. This means that the water still has magnesium and calcium in it, but instead of those minerals being in a form that is likely to cause scale build up in your pipes, plumbing, and appliances, it becomes simply a suspended particle.

Some examples of those water treatment options include electromagnetic water treatment, Capacitive Deionization (CDI), electricall induced precipitation systems, and Nucleation Assisted Crystallization (NAC) or Template-assisted Crystallization (TAC).


Studies suggest that NAC/TAC systems are around 90 percent effective in reducing scale build-up on water heating elements, and that the other systems are also effective, although not to quite the same degree.


NAC/TAC systems cost about the same as an ion-exchange system to install. They become depleted after about four years of average household use, and when that happens the media will need to be replaced. Prices for replacement media vary, but if the cost of the replacement media is averaged out over the four years, it's fair to say that it compares favorably with the salt, water and energy costs of running an ion exchange based water softener.


Whether an individual homeowner would prefer the lower maintenance and reduced running costs of a NAC/TAC system is a matter of personal choice. Remember that while ion exchange systems may cost slightly more to run, they do more than just stop scale buildup. Those who care about reducing residue on their dishes, or who want water that suds up nicely when they use bubble baths or fancy soaps might prefer the older technology.


In some parts of the world, NAC/TAC systems are already very popular. The technology was developed in Germany and has been widely adopted in mainland Europe for both residential and commercial use. It has passed NSF health and safety tests and is licensed for use in North America, so it will most likely start to become more widespread as more new builds include the technology, billing it as a low maintenance option.


Those who already have salt-based systems in their homes may struggle to make the change because it is true that the water "feels" different. Those who claim to notice a difference are most certainly not imagining it. Making the switch when moving, especially if moving to a city with a different municipal water supply or with water coming from a different reservoir, is a much easier proposition.

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