The Difference Between Water Softening and Reverse Osmosis

It can be easy to take water quality for granted, seeing as how we use it so much in our daily lives. We might rely on our local water supplier to purify what we use in our homes, but what if that isn’t enough?

It can be scary to think about the contaminants in our water. Can they cause health problems for my family? Or cause damage to my plumbing system?

There are home filtering systems that can eliminate particulates and contaminants. Two of the most common systems are water softeners and reverse osmosis. The main differences between them are that water softeners are less expensive, and reverse osmosis removes more contaminants.

Here, we will cover how each system works, their key differences, and which system might be better. With this information, you’ll be able to decide which water filtering system is best for your family.

What is water softening?

In some areas, hard water is an issue. This happens when the groundwater goes through mineral-heavy aquifers. In hard water, there is a high amount of heavy minerals that can be problematic for plumbing systems and washing. Calcium and magnesium are the most common minerals found in hard water. 

Over time, particles of calcium and magnesium build up in pipes and on plumbing fixtures like faucets and shower heads. This buildup can cause problems with water pressure and prevent proper functioning of the plumbing system.

Calcium and magnesium form bonds with cleaning agents in soap, creating an insoluble film that won’t rinse off of clothes or dishes. As a result of this, laundry washed with hard water can feel stiff, and dishes can have spots on them even after cleaning.

In an effort to combat this, scientists began to study ion exchange as a way to “soften” the hard water. They found that by passing hard water over a sodium enriched medium, the calcium and magnesium ions would essentially switch places with the sodium ions. 

With a lot of experimenting and research, scientists eventually introduced household water softeners in the 1950’s. These mechanisms attach to the incoming waterline, soften water by passing it through a medium, then the water is distributed throughout the plumbing network.

How Does a Water Softener Work?

A water softener system doesn’t only pass water through a medium, there is a lot more involved in the process. There are several components at work in these systems in order to make it convenient for homeowners.

A water softener system consists of two tanks-a resin tank and a brine tank. As the name suggests, the resin tank contains the sodium-enriched medium, or resin,  through which the hard water passes. The brine tank contains saltwater responsible for replenishing the resin with sodium after it is depleted by the softening process. This is known as the regeneration process.

There is also a control valve responsible for regulating and tracking the amount of water flow from the resin tank into the plumbing system. In some water softener systems, the control valve initiates the regeneration process once a certain amount of water has passed through the resin tank. In other systems, there is a mechanical timer that triggers the regeneration process at the same time every day. 

A lot of research and engineering has gone into developing these systems so that they are efficient, easy to operate and maintain, and reasonably economical for homeowners. Over the past few decades, these systems have become quite popular in areas with hard water.

Key Advantages of Having a Water Softening System

We mentioned how water softeners have become popular, and now we can explore the reasons why. As homes get bigger and have more extensive plumbing systems, the effects of hard water become a nuisance and can be expensive to deal with. Mineral buildup needs to be regularly cleaned to avoid damage to plumbing fixtures, and it can be very difficult or impossible to remove buildup from pipes. 

Here are some advantages to consider if you’re thinking about installing a water softening system.

  • Reduces damage to plumbing system

As we mentioned before, mineral buildup creates the need for regular cleaning of plumbing fixtures. It is more difficult to clean the insides of pipes, or components in water heaters, though. This leads to costly replacements over time, on top of regular maintenance that comes with owning a home.

  • Soap lathers and rinses better

Since calcium and magnesium create bonds with detergents, soaps aren’t allowed to lather as much as they would. Also, the scum that results from these bonds is practically insoluble, making it difficult to rinse off of laundry and dishware. This leads to uncomfortable, stiff clothing and linens, and spotty dishes.

  • Water heats faster

As we mentioned before, minerals can build up on essential components in a water heating system. Calcium and magnesium can form a scale on heating components, or build up in tanks, preventing heat from transferring to the water.

Disadvantages of water softening. 

While there are certainly perks to having a water softener, these systems are not without their downfalls. Here are some disadvantages to having a water softening system.

  • Requires maintenance

As we mentioned before, all appliances require maintenance over time. In addition to parts eventually requiring replacement, you will also need to replenish salt in a water softener, as well as the resin. While it isn’t terribly costly, it is an added hassle to normal household upkeep.

  • Removes essential minerals

While calcium and magnesium buildup can be problematic for our plumbing systems, it is essential for us to have these minerals in our diet. There are supplements available, but these are an added expense and it can be difficult to administer them to young children.

  • Doesn’t decontaminate water

These systems do well to remove calcium and magnesium, but water softeners do not remove lead or other harmful contaminants like bacteria. To remove these contaminants, a separate filter is necessary. These filters are easily installed, but need to be replaced frequently, and the cost adds up over time.

What is reverse osmosis?

As we know from science classes we took in school, osmosis is the process where the solvent in a less concentrated solution passes through a membrane into a more concentrated solution. This passive process dilutes the more concentrated solution to make both solutions equal. 

As the name suggests, reverse osmosis does the opposite by forcing the solvent in a highly concentrated solution through a membrane and into a less concentrated solution. In the water filtration process, the water is the solvent and calcium and magnesium are the solutes.  

Reverse osmosis is considered to be one of the most effective water filtration systems, as it removes the most contaminants and the technology is relatively simple.

How Does a Reverse Osmosis System Work?

As we mentioned, the reverse osmosis systems are very simple. A household’s incoming water system simply passes through a membrane, then this filtered water is distributed throughout the house. 

This filtering process requires pressure to push the water through the membrane, and the source of the pressure depends on the type of system. In tank systems, air pressure in the tank pushes the water through the membrane into a reservoir tank. In smaller-scale systems, pipe pressure pushes the water through a series of membranes. These smaller systems are typically installed under sinks. 

Advantages of Reverse Osmosis 

As we mentioned, reverse osmosis systems are considered to be one of the most effective ways to filter water. Here are some other advantages to consider.

  • Simple maintenance

Other than the typical maintenance that can be expected with household appliances, the only thing you have to worry about is periodically replacing the filter. Modern designs have simplified this process, and it should just take a few minutes. 

  • Removes most contaminants

Reverse osmosis can remove many more harmful elements than other systems. It has proven to be effective at removing bacteria and up to 99% of lead contamination.

  • Requires no chemicals to operate 

Unlike some other water purification systems, reverse osmosis is a purely mechanical process, and doesn’t require any substances to function. Added chemicals or ions used in other systems are consumed by the household and end up in groundwater, which can be harmful to some people and damaging to the ecosystem.

Disadvantages of reverse osmosis 

While they are considered to be the best in water filtration systems, reverse osmosis isn’t without its pitfalls. Here are some disadvantages to consider.

  • High installation cost

This system is one of the most expensive on the market. For a small system that fits under a sink, the cost can be $500-$800, while a large system that services the entire house can cost up to $10,000. 

  • Potential for low water pressure

Because reverse osmosis is a relatively slow process, the resulting water pressure can be low. This also depends on the capacity of your system and how extensive your plumbing system is.

  • Requires filter changes

Depending on your system, replacement membranes can cost around $50-$100. The frequency of changes depends entirely on the quality of water in your area, and how much you use.

Water Softener vs Reverse Osmosis-What’s the Difference?

Now that we know the advantages and disadvantages of each type of technology, it’s time to decide which one might be the best. There are many factors to consider, and here is where water softeners and reverse osmosis systems have the most significant differences.


Reverse osmosis is better at removing contaminants. While water softeners are good at removing the calcium and magnesium responsible for hard water, reverse osmosis also removes lead, bacteria, and other harmful contaminants. To determine whether you need all of the capabilities of reverse osmosis, you can have your water tested for these harmful contaminants. 


On average, reverse osmosis systems are much more expensive than water softeners. A water softening system can cost between $800 and $2,500, while a reverse osmosis system can cost up to $10,000. This is a very big difference, and can be the biggest determining factor for most homeowners.

Sodium in Softened Water

The trace amount of sodium in softened water can be harmful to those with certain health problems that require low-sodium diets. The amount of sodium that ends up in softened water depends on how hard the water was to begin with. The more calcium and magnesium in the hard water, the more sodium in the softened water. 

Now that we know what the biggest differences are, we can use this to determine which is better for our household. As we mentioned before, getting your water tested first will give us a good starting point. Once you know what you require from your system, the decision becomes easier.

Water Softener vs Reverse Osmosis-Which is Better?

While there are some big differences between the two systems, deciding which one is better depends entirely on your needs.

If you are concerned with the overall amount of contaminants in your water supply, reverse osmosis is the better option. However, if your water is testing very low for contaminants and mineral content is your only concern, a water softener is the most practical option.

Another aspect to consider is the cost. These systems vary greatly in installment cost, and a lot of us simply can’t afford an expensive water filtration system. To solve this, some homeowners have installed a water softener and added carbon filters to remove contaminants. While they are relatively inexpensive, carbon filters have to be replaced frequently, and the cost adds up over time.


Considering the advantages and disadvantages of water softeners and reverse osmosis, these are both good systems for filtering your water. Choosing which one is best for you comes down to your budget, and how much you want to filter your water. 

For those with several contaminants in their water supply, reverse osmosis may be the better option. If minerals in hard water are your main concern, a water softener will probably suit your needs.

With a bit of research on the quality of your water supply, and pricing the systems capable of servicing your home, this can be an easy decision.

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