Reverse Osmosis vs Water Softener: A Comprehensive Comparison

In recent years, homeowners and businesses alike have become increasingly concerned about the quality of water they consume and use in their daily activities. Consequently, water purification technologies such as reverse osmosis and water softeners have risen in popularity, offering differing approaches to improving water quality. This article delves into these two methods, exploring their mechanisms, benefits, and how they complement each other to achieve the best possible water purification results.

Reverse osmosis systems utilize a multi-stage filtration process that effectively removes up to 99.9% of total dissolved solids, including dissolved minerals found within water. This technology is favored by many individuals seeking high-quality drinking water, as it successfully eliminates impurities that water softeners alone cannot remove. In contrast, water softeners work by replacing magnesium and calcium ions with sodium ions, specifically targeting hardness minerals in water to soften it for general household usage.

The choice between reverse osmosis and water softeners largely depends on individual needs and the specific issues homeowners or businesses wish to address with their water supply. To achieve an optimal balance of purity and softness, some even choose to combine both systems. As we explore the pros and cons of each method, we aim to provide you with the necessary information to make an informed decision on the best water treatment solution for your needs.

Reverse Osmosis vs Water Softener: Basic Principles

Understanding Reverse Osmosis

Reverse osmosis (RO) is a filtration method that uses a semipermeable membrane to remove contaminants from water. This process works by applying pressure to force water through the membrane, allowing clean water to pass through while leaving behind dissolved solids and other impurities. Here are some key aspects of reverse osmosis:

  • Multi-stage filtration: RO systems usually consist of multiple filtration stages, including sediment filters, carbon filters, and the reverse osmosis membrane.
  • High removal efficiency: Reverse osmosis can remove up to 99.9% of total dissolved solids, including dissolved minerals, heavy metals, and other impurities.
  • Limited to drinking water: RO systems are typically installed under the sink and only filter the water you drink and use for cooking.

Understanding Water Softeners

Water softeners, on the other hand, are systems designed to treat hard water by exchanging magnesium and calcium ions with sodium ions. This process is known as ion exchange and results in softened water that is better for cleaning, washing hair, and protecting plumbing. Some features of water softeners include:

  • Ion exchange: Water softeners use a resin bed filled with sodium ions to exchange magnesium and calcium ions, effectively softening the water.
  • Whole-house treatment: A water softener treats all the water entering your home, ensuring softened water for all your needs.
  • Primary focus on minerals: Water softeners specifically target hardness minerals, such as calcium and magnesium, and do not remove other contaminants like reverse osmosis does.

By understanding the basic principles of reverse osmosis and water softeners, you can better decide which system is ideally suited for your needs. Remember, reverse osmosis systems focus on filtering contaminants, while water softeners primarily deal with softening hard water.

Key Components and Installation

Reverse Osmosis System Components

A reverse osmosis (RO) system consists of several components that work together to provide purified drinking water. Here are the key parts of an RO system:

  • Pre-filters: These filters remove larger particles, such as sediment and silt, to protect the delicate RO membrane from damage.
  • RO Membrane: The heart of the system, the RO membrane removes up to 99.9% of total dissolved solids, including various contaminants, ions, and minerals.
  • Post-filters: These additional filters polish the water further by removing any remaining tastes or odors.
  • Storage tank: This tank stores the purified water, ensuring a supply is available when needed.
  • Drain: The system discards impurities and contaminants, which are flushed down the drain.
  • Faucet: A separate faucet provides easy access to the purified water.

The installation of an RO system typically involves connecting it to the water supply, storage tank, and drain, as well as installing a separate faucet for the purified water output.

Water Softener Components

Water softeners are designed to treat hard water, helping to protect appliances and plumbing by exchanging magnesium and calcium ions with sodium ions. Here are the key components of a water softener:

  • Resin beads: These are negatively charged beads that attract mineral ions (calcium and magnesium) present in hard water.
  • Brine tank: This tank contains salt (sodium or potassium), which helps create a brine solution used during the ion-exchange process.
  • Control Valve: This component manages the flow of water through the system, as well as the regeneration process.
  • Mineral tank: This tank houses the resin beads and acts as the primary treatment area.

The installation of a water softener generally involves connecting it to the home’s main water supply line, positioning the brine tank, and ensuring proper connections to a drain or wastewater line.

Both reverse osmosis systems and water softeners serve different purposes in water treatment. While RO systems focus on providing purified drinking water, water softeners aim to protect appliances and plumbing by softening the water.

How They Work

Reverse Osmosis Process

Reverse osmosis (RO) is a multi-stage filtration system that removes up to 99.9% of total dissolved solids, including dissolved minerals such as magnesium and calcium, as well as a range of contaminants. The RO system utilizes an RO membrane as its core component, which acts as a barrier that only allows water molecules to pass through while trapping impurities.

The process typically involves the following stages:

  1. Pre-filtration: Sediment filter removes larger particles, like sand and silt, from the water.
  2. Carbon filter: Reduces chlorine and other chemicals that can damage the RO membrane.
  3. RO membrane: Separates water from dissolved minerals and contaminants.
  4. Post-filtration: A final carbon filter polishes the water, removing any remaining tastes or odors.
  5. Storage and pressure tank: A tank holds the purified water until it’s needed.

Water Softening Process

Water softening is a process that primarily targets hardness minerals, specifically calcium and magnesium. By exchanging these ions with sodium ions, water softeners effectively soften the water, improving its quality for various applications such as cleaning and washing.

The water softening process involves these key components:

  • Mineral tank: It holds the resin beads responsible for ion exchange. As hard water passes through the tank, calcium and magnesium ions are exchanged for sodium ions.
  • Brine tank: Contains a sodium solution to recharge the resin beads periodically. This ensures the efficiency and longevity of the water softening system.
  • Control valve: Regulates the flow of water through the mineral tank and initiates regeneration when needed.

While water softeners mainly address the issue of hard water, reverse osmosis systems provide a more comprehensive water filtration solution. To achieve optimal water purification, many homeowners and businesses combine both technologies. This ensures removal of a wide range of impurities, improving water quality, and protecting plumbing systems from the effects of hard water.

Maintenance and Costs

Reverse Osmosis System Maintenance and Cost

A reverse osmosis (RO) system requires periodic maintenance to ensure optimal performance. This includes:

  • Replacing the pre-filter and post-filter every 6-12 months, depending on usage and water quality
  • Replacing the RO membrane every 2-3 years
  • Cleaning the storage tank and checking for leaks

The cost of maintenance for an RO system is relatively low. Whole-house reverse osmosis systems can cost anywhere from $750 to $7,500 for installation, depending on your home’s size1. Replacement filters can range from $50 to $150 per year, depending on your system and water usage.

One downside to RO systems is that they produce wastewater during the filtration process. This can increase your water usage and potentially your utility bill.

Water Softener Maintenance and Cost

A water softener system needs regular maintenance to maintain its efficiency. Common maintenance tasks include:

  • Adding salt to the brine tank (usually every 4-6 weeks)
  • Regularly checking the salt level and ensuring it doesn’t form a solid crust (known as a salt bridge)
  • Cleaning the resin tank and control valve periodically
  • Monitoring the system for any leaks or malfunctions

The average price for professionally installing a whole-home water softener system is $1,5002. This cost includes both materials and labor. The type of system you choose could influence costs; they can start from $500 and go up to $6,0002. You’ll also need to budget between $10 and $50 per month for salt and system maintenance2.

In summary, both reverse osmosis and water softener systems have different maintenance requirements and costs. An RO system typically has lower maintenance costs but higher installation fees, while a water softener has higher ongoing monthly costs due to salt use and potential plumbing issues.

Effectiveness in Treating Water

Reverse Osmosis System Effectiveness

Reverse osmosis (RO) systems are highly effective when it comes to water purification. These multi-stage filtration systems work by forcing water through a semipermeable RO membrane, which removes up to 99.9% of total dissolved solids, including dissolved minerals, particles, and bacteria1. In addition to the RO membrane, these systems usually include pre-filters and post-filters which handle contaminants like chlorine, sediment, and other impurities.

There are several benefits to using an RO system:

  • It removes a wide range of contaminants, making your water safe to drink.
  • The purified water has a clean, fresh taste due to the removal of impurities.
  • RO systems prevent the build-up of bacteria, ensuring continuous purification.

However, it’s important to note that reverse osmosis systems are installed mainly for drinking and cooking purposes and are not designed to treat the entire household water supply.

Water Softener Effectiveness

Water softeners are specifically designed to address hard water problems. They work by using an ion exchange process, in which the resin media inside the softener replaces calcium and magnesium ions, responsible for water hardness, with sodium ions2. This results in soft water, which has several benefits for your home:

  • Reduces scale build-up in pipes, appliances, and plumbing fixtures.
  • Improves the efficiency of water heaters.
  • Enhances the cleaning abilities of detergents and soaps, making it easier to wash clothes, dishes, and even your hair.

However, it’s crucial to understand that water softeners are not meant for water purification. They do not remove contaminants like bacteria, viruses, or dissolved organic matter.

In summary, reverse osmosis systems and water softeners tackle different water issues. RO systems focus on water purification, removing an extensive range of impurities, but are limited to drinking and cooking water. Conversely, water softeners specifically address water hardness issues, benefiting the entire household but not providing complete purification. Choosing between the two technologies depends on your water issues and your household preferences.

Advantages and Disadvantages

Pros and Cons of Reverse Osmosis Systems


  • Highly effective filtration process: Reverse osmosis (RO) systems remove up to 99.9% of total dissolved solids, including dissolved minerals, lead, and other contaminants (1). RO is considered one of the most effective methods of water filtration (2).
  • Removes pathogens and viruses: The RO membrane is capable of filtering out harmful pathogens and viruses, providing safe and pure water for consumption (3).
  • Improved taste: RO systems typically include a carbon filter which removes chlorine and other chemicals that could affect the taste and odor of water, resulting in more natural and better-tasting water (4).


  • Expense: RO systems can be more expensive to install and maintain compared to water softeners (5).
  • Wasteful process: The filtration process of RO systems generates a significant amount of brine (waste water) which can raise environmental concerns and limit its use in areas with water scarcity (6).

Pros and Cons of Water Softeners


  • Effectively softens water: Water softeners exchange magnesium and calcium ions with sodium ions, reducing limescale and soap scum buildup in plumbing and appliances (7). This extends the life of appliances and improves the efficiency of soap and detergents (8).
  • Whole-home solution: Water softeners treat all the water in the home, making it ideal for cleaning, washing, and other household activities (5).


  • Limited filtration capabilities: Water softeners primarily focus on softening water by reducing mineral content and do not effectively remove other contaminants like dissolved solids, pathogens, and chemicals (9).
  • Brine tank maintenance: Water softeners require a brine tank to facilitate ion exchange, which needs regular maintenance and refilling with salt (10). This may be a disadvantage for those who want a low-maintenance solution.
  • Possibility of altered taste: Water softened with a water softener may have a detectable change in taste due to the sodium ions used in the ion exchange process (1).

Using both RO and water softener systems in combination can result in comprehensive water treatment, providing both softened and purified water throughout the household (5).

Considerations for Your Home

Deciding on a Reverse Osmosis System

A reverse osmosis (RO) system is a multi-stage filtration process that removes up to 99.9% of total dissolved solids, including dissolved minerals through a semi-permeable membrane. It helps in providing clean water for drinking, usually installed under the kitchen sink.

When deciding on an RO system, check your household water pressure, as adequate water pressure is essential for the RO system to operate efficiently. Assess the presence of contaminants, such as iron or specific health risks, by testing your water, which will further help in determining the need for RO in addition to a sediment filter.

An RO system requires minimal maintenance, but it’s essential to replace the filters, including the semi-permeable membrane, as recommended by the manufacturer to ensure optimal performance.

Deciding on a Water Softener

A water softener’s primary function is to remove hardness minerals, such as calcium and magnesium, which result in hard water. Hard water causes limescale buildup on plumbing fixtures, appliances, and can decrease the efficiency of your water heater.

Consider the following when deciding on a water softener:

  • Assess the water hardness: Test your water for hardness levels to determine the need for a water softener.
  • Calculation of daily usage: Determine the daily water usage in your household to choose the right water softener size.
  • Select a type of water softener: There are different types of water softeners: ion exchange, salt-free, magnetic, and electronic descaler. Each type has its pros and cons, select based on your requirements and budget.
  • Maintenance requirements: A water softener requires regular maintenance, such as replenishing the salt tank, cleaning the brine tank, and monitoring the regeneration cycle.

Both systems serve different purposes, though they can be combined in certain situations. Understanding the specific needs of your home will guide you toward the best decision for choosing a water treatment system.

Combination Systems

Combination systems utilize both reverse osmosis and water softener technologies to provide comprehensive water treatment solutions for households. By combining these two methods, users can benefit from the high-quality purified water that meets their specific needs.

Reverse osmosis systems consist of multiple filtration stages that efficiently remove small particles, dissolved solids, and harmful contaminants from water sources. These stages generally include a sediment pre-filter, an activated carbon filter, a reverse osmosis membrane, a carbon post-filter, and sometimes a remineralization filter. With this setup, reverse osmosis filters out excess minerals, VOCs, and other contaminants to produce purified water.

Water softener systems, on the other hand, focus mainly on eliminating calcium and magnesium minerals from water. Through the ion exchange process, water softeners tackle hard water issues, which can lead to dry skin, hair problems, and mineral deposits on plumbing systems. By swapping calcium and magnesium ions with sodium ions, water softeners contribute to the overall longevity of your household appliances and plumbing system.

Combination systems are designed to be Point-of-Entry (POE) or Point-of-Use (POU) depending on the user’s needs. POE systems treat the water as it enters the house, while POU systems treat water at specific locations within the house, such as the kitchen sink. These setups can offer a tailored approach to water treatment, addressing specific household needs more effectively.

The control valve in a combination system is responsible for managing the balance between filtration and softening processes. Regular regeneration cycles ensure that the system’s efficiency and effectiveness are maintained over time. According to the US Geological Survey, combination systems can be adjusted to meet the varying hardness levels and mineral contents found in different water sources, providing optimal water treatment for each unique situation.

In conclusion, combination water treatment systems offer the best of both reverse osmosis and water softener technologies, addressing a wide range of water quality issues. They are efficient in providing purified water while also protecting your appliances and plumbing systems from hard water damage. By considering the specific needs of your household, combination systems can be designed and adjusted to provide the most appropriate water treatment solution.


  1. Average Reverse Osmosis System Costs In 2023 – Forbes Home 2
  2. How Much Does a Water Softener System Cost? (2023 Guide) – This Old House 2 3 4