What Are the Different Types of Reverse Osmosis Filter Systems?
Written by: Gene Fitzgerald // Last Updated: Jul 21, 2023
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When it comes to reverse osmosis systems, there are various types, each with its own unique features and applications
This article will delve into the world of RO systems, exploring the most important and commonly encountered varieties.
Let’s go!
Contents
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Key Takeaways
- The different types of reverse osmosis systems are countertop, under sink, and whole house models.
- Subtypes of these models include tank systems, tankless systems, proprietary and non-proprietary systems, and 3, 4 or 5-filtration stage systems.
- There are also reverse osmosis system types for various industrial applications.
What Are the Different Types of Reverse Osmosis Filter Systems?
So, what are the different types of reverse osmosis systems? There can be many different types of reverse osmosis systems, depending on how you group them.
Countertop, Under Sink, and Whole House-Type Reverse Osmosis Systems
The most common type of reverse osmosis system available in the market today is point-of-use systems. These systems are typically set up beneath a kitchen sink, filtering only the drinking water that’s dispensed from a separate faucet located on the countertop. Since this type of RO system focuses solely on purifying drinking and cooking water, they offer efficiency and require relatively simple maintenance.
This is in stark contrast to whole house or point-of-entry reverse osmosis systems that purify the entire water supply for your home. While these may seem appealing in their design, they often come with significant purchase, installation, maintenance, and operational expenses, making them financially unfeasible for most individuals.
There are also countertop versions of RO systems. These units sit atop a counter and function similarly to under sink models but create water on demand rather than utilizing a storage tank.
Benefits of Under Sink Reverse Osmosis Systems
All types of reverse osmosis systems provide purified water that’s much safer for drinking.
But there are several benefits specific to an under sink reverse osmosis system. They include:
- Space savings: The primary benefit of under sink RO systems is that they take up significantly less space than their whole house counterparts. This makes them perfect for small apartments or houses. Also, they won’t use any valuable countertop space.
- Cost-effective installation and easy maintenance: Under sink reverse osmosis systems are relatively simple to install and maintain, making them highly cost-effective.
- Customizable: Under sink RO systems can usually have components added to them for customization, such as remineralization filters or lines to coffee machines and refrigerators.
Benefits of Countertop RO Systems
- The filtration process is quick: Countertop RO systems can be installed in just a few minutes without extensive plumbing or drilling. This temporary installation is ideal for rentals.
- Maintenance is straightforward and cost-effective: The upkeep of a countertop-type RO filter is simple and cost-effective; you can easily do it yourself.
- Compact and easily portable: All countertop reverse osmosis water filter systems have a compact design for small countertops. Some are even travel-friendly, making them perfect for on-the-go use.
Benefits of Whole House RO Systems
- Healthier skin and hair: The purification process removes harmful contaminants like lead, heavy metals, and chemicals, providing safer water for consumption and use – all throughout your home! This results in healthier skin and hair due to softer water and less chlorine exposure when showering or bathing.
- Protects your home’s plumbing: The system also protects your home’s plumbing and appliances by preventing damage from hard water, iron, sediments, etc.
- Removes hard minerals: Daily chores like dishwashing become quicker due to the absence of hardness minerals.
- Increase property value: Installing a whole house reverse osmosis system can increase your property’s value. Potential buyers may appreciate the benefits of purified water, and its environmentally friendly aspect could be an added selling point.
Tank-Type vs Tankless Reverse Osmosis Systems
Tank-Type and tankless RO systems have the same goal of purifying water but differ in their design and functionality.
Tank-Type Reverse Osmosis Systems
These systems have a storage tank where filtered water is stored. The purification process in these systems can be slow, so they hold water to ensure you have access to purified water anytime you need it. A tank-based RO tends to occupy more space due to the presence of the tank. However, it can provide a steady supply of filtered water even during periods of heavy usage.
The pressurized storage tank facilitates the distribution of water throughout the system as per demand. It also utilizes pressure to activate the automatic shut-off valve.
Tankless Reverse Osmosis Systems
These systems do not have a storage tank. Instead, they purify water on demand. This results in fresher water, which doesn’t sit in a tank for extended periods. Tankless also takes up significantly less space, making it ideal for smaller households or places with limited space.
Another benefit of going tankless: It often produces less wastewater and is typically more energy-efficient. However, the flow rate will be slow.
If you want a tankless reverse osmosis system for under your sink, a pressure pump is required. Without a pump, there won’t be enough pressure to pump water up the sink. So tankless and pumpless only goes only with countertop models.
Different Stages of Filtration
We can also group reverse osmosis systems into different types based on the number of filter stages they use. Most common are 3-stage, 4-stage, and 5-stage systems.
3, 4, and 5-StageReverse Osmosis Filter Systems
The filter options in a reverse osmosis system are as follows:
- Pre-filters: These are responsible for the initial filtration stage. They eliminate various impurities from the water before it reaches the reverse osmosis membrane. Without pre-filters, the RO membrane would be susceptible to quick clogging and potential malfunction. Common configurations often consist of 1 or 2 sediment filters and a single or two carbon filters.
- Reverse Osmosis Membrane: Serving as the heart of the system, the reverse osmosis membrane carries out the bulk of the filtration work. This component is capable of removing a vast array of contaminants effectively.
- Carbon Post-Filter: A carbon post-filter is responsible for the final refining touches, enhancing the aroma and flavor of the purified water that has been stored in the tank.
- Remineralization: One significant drawback of reverse osmosis is its tendency to remove all naturally occurring minerals from water. For individuals who rely on their daily water consumption for mineral intake, this could pose a problem. A potential solution is to incorporate a remineralization filter into the system, which reintroduces these essential minerals back into the water.
- UV Filter: A UV filter can be used to eliminate microorganisms.
If you have a 4-stage system, it usually means 1 sediment pre-filter, 1 carbon pre-filter, RO membrane, and the carbon post filter. A 3-stage system has a carbon pre-filter, the RO membrane, and a carbon post filter.
A 5-stage reverse osmosis system offers a variety of filter configurations.
- You have the option of using 3 pre-filters (2x sediment + 1x carbon), followed by the RO membrane and a carbon post-filter.
- Alternatively, you can choose 3 pre-filters (1x sediment + 2x carbon), with the RO membrane and carbon post-filter.
- Another option is 2 pre-filters (1x sediment + 1x carbon), followed by the RO membrane, carbon post-filter, and remineralization filter.
- Lastly, you can opt for 2 pre-filters (1x sediment + 1x carbon), the RO membrane, carbon post-filter, and UV lamp.
Remineralization Filters
The majority of under sink reverse osmosis systems offer a degree of customization, including the option to include additional filtration stages. One is the inclusion of a remineralization filter.
This filter can help to balance the pH of the water and reintroduce essential minerals and trace elements that were removed during the filtration process, such as calcium carbonate, potassium chloride, magnesium sulfate, and sodium bicarbonate. The specific minerals reintroduced can differ depending on the filter.
Types of Reverse Osmosis Membranes (TFC vs CTA)
There are two main kinds of reverse osmosis membranes used in homes: Thin-film composite (TFC) and cellulose triacetate (CTA).
- TFC membranes, made of a reinforced acrylic polymer, are the most popular choice for home RO systems. They are better at filtering out salts than CTA membranes, but chlorine can easily damage them.
- CTA membranes, on the other hand, are made from a type of processed cellulose. They can withstand chlorine better and are usually cheaper, making them a common choice for larger water treatment systems.
Even though TFCs are generally more effective, they’re vulnerable to chlorine damage. That’s why having a working carbon pre-filter in your RO system is crucial. This pre-filter removes chlorine before it can reach and damage the TFC membrane.
When comparing RO membranes for home use, there are notable differences between the two types. TFC membranes are pricier and less chlorine-resistant but have a higher overall TDS rejection rate. On the other hand, CTA membranes are cheaper and more resistant to chlorine.
CTA reverse osmosis membranes also permit a significantly higher amount of iron in the feed water than other types. If your water has high iron content and you prefer a TFC membrane, it’s advisable to use an iron removal pre-filter.
Proprietary vs Non-Proprietary RO Water Filters
One final way to group reverse osmosis systems into different types is proprietary vs non-proprietary models.
In general, there are standard-sized non-proprietary RO systems that often share similar design features. Most importantly, the filter sumps + cartridges (the part of the unit where the water is held for filtration) in vertical configurations and the horizontal filters on top commonly use standardized sizes. This standardization means you have the flexibility to use filter elements from various brands, allowing for customization or cost-saving measures.
Proprietary RO Water Filters are specific to certain brands or models of RO systems. These filters are designed and engineered by the system manufacturer, and you typically need to go back to the original manufacturer or authorized seller to get replacements. They often claim that these filters have unique features or superior performance tailored for their specific systems.
However, this could potentially pose problems. For example, what if the company’s filters are costly? Or what if the company goes out of business or discontinues the product line? These are crucial factors to consider when choosing between a standard or proprietary water filtration system.
Further Reading:
Industrial RO Types
For sake of completeness, we quickly wanted to mention industrial RO types. There are various, each designed to meet specific water purification needs. Here are some examples:
- Desalination System: This type of RO system is engineered to desalinate seawater, making it safe for consumption or use in irrigation and other applications. It’s particularly useful in coastal areas or regions with limited freshwater resources.
- Brackish Water System: This system treats water with high salinity levels, typically dirtier than tap water. It’s often used in areas where groundwater or surface water has high salt content.
- Water Treatment Plants: These large-scale plants can treat vast amounts of surface water, brackish water, and seawater. They’re typically employed by municipalities or industries that require a substantial quantity of clean water.
What Is the Reverse Osmosis Process Exactly?
Reverse osmosis systems use water pressure to force water through an ultra-fine membrane that captures contaminants as small as .0001 microns, including microbial contaminants, heavy metals, and salts.
Osmosis is a natural process where water from a weaker saline solution moves through a membrane into a stronger saline solution to balance salt concentrations. Reverse osmosis is the opposite of this process. It uses external pressure to push water from the stronger saline solution (unfiltered water) through the membrane into the weaker saline solution (filtered water). This requires energy in the form of pressure. The membrane rejects floating contaminants and dissolved solids on the waste side, which is then discarded through a drain line.
If you have any questions about RO types please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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