How to Choose a Reverse Osmosis System
Written by: Alexandra Uta // Last Updated: Sep 1, 2023
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Even though reverse osmosis systems are relatively simple in how they work, choosing one is far from straightforward, especially if it’s your first time exploring this market.
We’ve prepared this handy RO buying guide that highlights the most important features of household reverse osmosis systems – hopefully it will point you in the right direction!
Contents
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Key Takeaways
Here are the most important questions to ask yourself when choosing a reverse osmosis system:
- Do you want to filter your entire household’s water supply, or just at a specific point like the kitchen faucet?
- How much free space do you have available?
- How much RO water do you need on an average day?
- What kinds of water contaminants do you want to remove?
- What’s your short-term and long-term budget?
Once you have answers to these questions, you can go out and buy a reverse osmosis system. But remember to watch out for products with NSF certifications and try to match the filtration process to your water requirements. Also, consider short and long-term cost – think filter replacements.
How to Choose a Reverse Osmosis System
So, how do you choose a reverse osmosis system?
Choosing a reverse osmosis system starts with identifying your requirements. The most important factors to consider include:
- Do you want to filter your entire household’s water supply, or just at specific points like the kitchen faucet?
- How much space do you have available?
- How much (drinking) water does your household consume on a daily basis on average?
- What kinds of contaminants do you need to remove?
- What’s your budget? Both in the short and long term.
The answer to the first question will tell you whether you need a whole house RO system or a point-of-use one. After that, your space requirements and consumption habits will point you in the direction of either an under sink model, or a countertop one. If you consume a lot of water and/or don’t have much space available on your counter, you’ll most likely want an under sink reverse osmosis system. On the other hand, a countertop model provides you with some extra portability in case you frequently shift things around in your kitchen or move between different places.
Once you know what kind of reverse osmosis system you want to buy, you should have your water tested to find out what contaminants you’re dealing with. This will narrow down your search to models that specifically cover those contaminants. Pay attention to NSF certifications!
At this point, you’ll likely end up with several models at different price levels. Spending more on a higher-end model usually allows you to save some money on its maintenance in the long run. With that in mind, try to pick something that’s suitable not only for your immediate financial situation, but your long-term plans as well.
What Is a Reverse Osmosis System and How Does It Work?
What is a reverse osmosis system in the first place though? In short, it’s a multi-stage filtration system that is very thorough at removing impurities and contaminants from water, even in cases of heavy contamination. At the heart of this system is the reverse osmosis membrane. This membrane is lined with very tiny pores, usually around 0.0001 microns in size. That’s so tiny that only water molecules can pass through them. Water is pushed against this membrane using high pressure. Once it hits the membrane, contaminants aren’t able to pass through the pores and get sent away with the wastewater stream.
The reverse osmosis membrane does a lot of the work, but it’s not the only treatment element in the typical household reverse osmosis system. Normally, you’d also have one or more pre-filters as well as one or more post-filters which further treat your water for various types of contamination.
Most pre-filters are designed to improve the effectiveness of the reverse osmosis membrane itself by removing contaminants which can compromise it. Post-filters are used to further purify water in ways that the reverse osmosis membrane alone can’t achieve. Dissolved gases are one of the most prominent examples of contaminants that require additional treatment.
Many household reverse osmosis systems also feature a storage tank. This is useful due to the slow operation of the reverse osmosis process. Without a storage tank, you’d have to wait a long time every time you wanted to grab a glass of water. However, some users prefer a tankless configuration instead, especially when the amount of space available for the installation of the system is limited.
The Types of RO Systems for Home Use
Household reverse osmosis systems are generally sorted into three categories: under sink, countertop, and whole house models. Each version has its advantages and disadvantages, and your choice should be aligned with lifestyle factors like the size of your household and the water consumption habits of you and those you live with.
Under Sink
Under sink reverse osmosis systems are commonly chosen by people who don’t need whole house filtration, and also don’t have a lot of countertop space available. As the name implies, these models fit comfortably in the cabinet under your sink, and are usually completely out of your sight. They also tend to be more customizable than countertop systems, allowing you to easily add different filtration stages according to your specific needs.
Countertop
Countertop reverse osmosis systems, on the other hand, are ideal when you don’t want to go through any complicated installation procedures, or only need a temporary solution. They are also useful for traveling, as some models only require minimal plumbing connections to work and don’t require any permanent modifications to your current setup. In most cases, you don’t even have to drill any holes in your countertop. These models require the least amount of maintenance of the three types, and they also tend to be cheaper.
Whole House
A whole house reverse osmosis system is installed at the point where water enters your home, and therefore filters all water passing through the house. This means that you’ll not only have reverse osmosis water for drinking, but also for showering, washing your dishes and clothes, and any other household uses you can think of. This brings various benefits to the table, such as potential improvements to your skin and hair health, as well as reduced wear on your plumbing.
Buying Guide: What to Consider When Choosing a Reverse Osmosis System
So, with all that in mind, how should you go about choosing a reverse osmosis system for your home? Your decision should be based on several factors, which we’ve listed below. Note that some of those points might not be relevant to everyone, but this list is still a good starting point for your search.
System Type
First, decide on the exact type of reverse osmosis system that you want to use. This mainly depends on whether you insist on whole house filtration, and the amount of space you have available.
If you’re renting and don’t own the property, a whole house system will likely be out of the question. Even an under sink model might require modifications that your landlord won’t agree to. Under sink and countertop models tend to be the most popular among regular domestic buyers in our experience. But if you insist on filtering the entire supply of water in your household, a whole house system is the only option.
Further Reading:
Your Contamination Situation
Next, you should get an overview of your current water contamination situation. This will allow you to pick a suitable configuration of different pre and post-filters. The easiest way to do this is by buying a DIY water test kit, which you can find at any hardware store.
However, this will only inform you about the presence of certain contaminants, so if you want to see the full picture, you’ll need to send a sample of your water to a laboratory to have it evaluated. This will provide you with a complete overview of your water quality, and you’ll know exactly what issues there are to address.
NSF Certifications
Paying attention to NSF certifications is a good way to ensure that the RO system you’re buying has been specifically tested against certain types of contaminants, and that it’s made of high-grade materials. There are many different NSF certifications, each covering specific contaminants or groups of contaminants. Here are some common examples to watch out for:
- NSF Standard 42 is related to water aesthetics, chlorine taste and odor being the most notable example. This is a good certification to have in general, as it also indicates that the product was made with safe materials and production processes.
- NSF Standard 53 relates to different health-affecting contaminants, such as cysts, heavy metals, and other substances that could impact your well-being.
- NSF Standard 58 is particularly important for reverse osmosis systems, as it’s specifically related to their performance. It indicates that the system can deal with a number of specific contaminants, such as chromium, arsenic, lead, and nitrate, but also that it reduces TDS (Total Dissolved Solids) levels by a certain amount.
Pre and Post-Filters
Knowing what kinds of contaminants you’re dealing with will also allow you to pick suitable pre and post-filters for your RO system. You should ideally try to cover these points:
- Pre-filters: use at least one or two sediment filters, and at least one carbon filter – two are recommended in cases of more severe contamination.
- Post-filters: activated carbon is also useful as a post-filter, especially when it comes to removing contaminants like dissolved gases which might not get properly filtered out by the reverse osmosis membrane. A UV filter can eliminate all bacteria and other biological contaminants. Finally, a remineralization filter is also useful to consider, as it can help compensate for the minerals that get taken away by the reverse osmosis process.
Your Water Consumption Habits
You should also think about your water consumption habits – as well as those of your entire household, if you live with other people. If you live in a larger home with multiple people who drink a lot of water, a countertop model will likely not suffice – or you may need to purchase more than one. An under sink model is a better option in this case, but you might have to get a larger storage tank.
Initial and Long-Term Cost
There’s usually a fine balance between the upfront cost of a reverse osmosis system and the long-term costs associated with maintaining it. Spending more on an expensive system may result in some savings down the road, as you won’t have to invest that much in its maintenance. On the other hand, a cheap system may break down more often or require more frequent filter replacements.
The Pros and Cons of Reverse Osmosis
Pro: Always Have Fresh, Clean Water
With a reverse osmosis system, you’ll always have access to fresh, clean water on demand. As long as you pick an adequately sized storage tank, you should never have to wait before the system can dispense water.
Pro: Stop Buying Bottled Water
Tired of lugging crates of water bottles from the store every week? You can forget about that! You will never have to buy water from the store again, at least when you intend to consume it at home. As an added bonus, you’ll also stop contributing to global pollution with all the plastic waste generated from those bottles.
Pro: Improved Taste and Smell of Water
Some people avoid drinking tap water because they dislike its taste. That’s something else reverse osmosis can fix. Since your water will contain no contaminants after passing through the reverse osmosis system, it will also have no smell or taste at all. After all, pure water is completely tasteless and odorless, and those factors are caused by the presence of various contaminants.
Pro: No Power Required
A reverse osmosis system doesn’t need power by default – only sufficient pressure. In some cases, you might need to run a pump to balance issues with your plumbing’s pressure, but other than that, you don’t need to supply the system with power to keep it running.
Pro: No Chemicals
Water is purified by pushing it through the RO membrane, and no chemicals are added to it at any point. This makes reverse osmosis a more attractive treatment method for some people who dislike the idea of mixing chemicals into their water supply.
Pro: Easy Maintenance
Compared to other types of water treatment systems, reverse osmosis systems are very simple to maintain and require relatively little work in the long term. You’ll have to replace the membrane regularly – typically once every 2-5 years, although this will vary a lot depending on your circumstances. Other than that, you must replace the pre and post-filters according to their individual requirements, and you may occasionally have to replace some of the valves or pieces of tubing as they degrade over time.
Con: Wastewater
Probably the biggest downside of reverse osmosis is that it wastes a lot of water. The ratio is not negligible – by default, the process wastes 3-5 gallons for each single gallon of purified water.
If this sounds too much for you, keep in mind that you can alleviate the situation in various ways. For example, you can lower wastewater production by using a pressure pump, you can reuse wastewater for other purposes like gardening, or you can refilter it to improve the wasted/filtered water ratio.
Con: Slow Operation
Reverse osmosis takes time to work. It’s not a process that can serve you with clean water on demand. That’s why domestic systems typically incorporate a storage tank. It serves as a buffer, ensuring that you always have access to purified water whenever you need it. Your storage tank doesn’t need to be too large either – just enough to provide your household with water for 12-24 hours.
Con: Water Might Taste Flat
You might be used to having a certain taste in your water, which will disappear once it’s been treated with reverse osmosis. There’s unfortunately no way to negate that. You can look into mineral drops or a remineralization filter to reintroduce some minerals back into your water, but that won’t guarantee that you’ll get the exact original taste back.
Con: No Minerals Left
Speaking of remineralization, reverse osmosis also removes healthy minerals from water. Thus, consider remineralization!
Con: Space Requirements
No matter what kind of reverse osmosis system you choose, it will always require some space. Either on your countertop, under your sink, or elsewhere in the house (if using a whole house setup). If you live in a small apartment where every square inch is a precious resource, you might have to plan ahead in order to fit in a reverse osmosis system.
If you have any questions about our reverse osmosis system buying guide please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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