Do I Need a Reverse Osmosis Water Filter System? Why?

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Reverse osmosis is the most effective method of home water filtration.

But whether or not you’ll need a reverse osmosis system in your home will depend on several factors.

Let’s discuss these factors and analyze your need for reverse osmosis!

Key Takeaways

  • Reverse osmosis is one of the most effective home water filtration methods, but it isn’t always necessary.
  • If your water supply is heavily contaminated – then an RO filter system is often the best solution for purification. These systems will remove a wide array of contaminant types at a reasonable price point.
  • To achieve a similar purification level to an RO system one would need to combine several different filtration methods like activated or catalytic carbon + KDF media + ion exchange.
  • To determine if you need an RO system first you’ll need to test your water quality. Ideally, this can be done through professional testing. You could also use a home test kit or check the latest water report if you are on municipally-supplied water.

Do I Need Reverse Osmosis?

“Do I need reverse osmosis?” is a question we get asked a lot.

You need a reverse osmosis system if your water conditions demand it.

Reverse osmosis is exceptionally effective at removing a wide array of water contaminants due to the mechanics of its ultra-fine semi-permeable membrane: Feed water is forced under pressure through said membrane – which rejects and separates almost all impurities in a waste water stream which is flushed down the drain.

We’ll discuss all the types of water contaminants reverse osmosis can remove in a bit. For now, all you need to know is that reverse osmosis removes pretty much everything from water providing almost pure H2O, which also improves water taste obviously.

And in addition to the reverse osmosis membrane, RO systems use several pre-filter stages to remove even more pollutants and protect the RO membrane from damage. Most units will include an activated carbon pre-filter to remove chlorine/chloramine as well as a sediment pre-filter to remove sand, silt, and other dirt.

Bottom line: If your water supply is heavily contaminated, an RO system is often the best solution – as it provides a high degree of filtration at an affordable price point. Alternatively, if your water quality is already quite good or you wish to remove just one specific contaminant (type), then an RO system might be overkill.

By the way, if you were hoping to achieve a level of water filtration comparable to an RO system, you would need to combine several advanced filtering methods. Activated/catalytic carbon plus ion exchange plus a KDF media filter might get you a similar level of contaminant removal. But why not combine all in one stage?

How You Can Test Your Water

Water Testing Report

Before purchasing any filter system, the first step is getting your water quality professionally tested. This will mean conducting a water quality test of some type.

If your water is sourced from a well, then you can send a sample to an independent lab for testing. This is the most accurate way to assess contaminants and their quantities – but will cost several hundred dollars. You can also order a home test kit, which will cost significantly less but won’t give very accurate figures. You’ll also be limited in the types of water contaminants you can test for.

If your water is municipally sourced, then you can also look up the latest water report published by your water utility. You can get in touch with your water provider directly or use EWG’s Tap Water Database. Keep in mind these reports won’t give you any information on the service lines running into your home, which can leach contaminants in certain cases.

Once you have a good idea of the contaminants you’ll be dealing with, then determining if an RO system is right for you will be much easier.

Benefits: Why Do I Need a Reverse Osmosis System?

Contaminant Removal

Reverse osmosis systems excel at broad-based contaminant removal, which means they remove nearly everything from water except for pure H2O. RO systems will effectively remove chlorine/chloramine, pesticides, bacteria and other microbial contaminants, heavy metals, minerals, and salts etc.

Clean Drinking Water

After contaminants have been removed from your water, you’ll be left with exceptionally pure and clean water. This water not only makes great drinking water, but it’s also ideal for cooking and brewing coffee or tea.


RO water has a superb taste and smell owing to its low level of contaminants. It’s very neutral tasting.

Filtered Water on Demand

Reverse osmosis filtration is a slow process, which is why most home RO systems feature a storage tank to keep filtered water on tap at all times. This means you won’t need to wait for the system to filter water when you pour a glass.

Reduce Bottled Water Usage

If you’ve been using bottled water as your drinking water source, then installing a reverse osmosis system will save you significant money and reduce your plastic waste. Plastic waste is a serious environmental issue, so cutting down your plastic usage is a great idea.

Cost Savings

A decent point-of-use RO system starts at just several hundred dollars and will pay for itself in the first year when compared to bottled water. Additionally, once you’ve purchased a system, the only ongoing costs are filter and membrane replacements.

Installation and Maintenance

Point-of-use RO systems are easy to install and can be installed on your own provided you have basic DIY and plumbing knowledge. These systems are installed under a kitchen sink and only filter water coming out of a single faucet.

Point-of-entry systems – also called whole house systems – filter all of the water coming into your home and are more complex to install.

As far as maintenance goes, most RO systems only require biannual/annual pre and post-filter changes, membrane replacement every 2 to 5 years, and cleaning/sanitizing of the tank every 6 to 12 months.


Many RO systems feature a modular design that allows you to add additional filter stages should you wish.

When Is a Whole House Reverse Osmosis System Necessary?

A whole house reverse osmosis system is generally not necessary when you have municipally supplied water. For most applications, an under sink RO system is more than enough, as it will filter all of the drinking water coming out of your kitchen faucet.

If your water is highly contaminated – which generally is only the case for well water in rural areas – then a whole house reverse osmosis system may be needed.

Once again, the only way to determine the quality of your water is to get it professionally tested. If you’re considering a whole house RO system, then the cost of professional water testing is easily justified.

Reverse Osmosis Disadvantages

It’s not all positive when it comes to reverse osmosis. There are also several drawbacks to consider before you commit to purchasing.

Under Sink Reverse Osmosis System

Flat Taste

While RO water is exceptionally pure, some people find it has a flat taste when compared to other water types. Most people get used to this in time, but if this is an issue for you, then installing a remineralization stage will add back essential minerals and improve the taste.

Mineral Loss

Reverse osmosis is so effective that it removes both harmful contaminants and healthy minerals like potassium, magnesium, and calcium. This is not a major issue as drinking water is not a major source of essential minerals for people, but once again, a remineralization stage solves this issue.


RO systems unavoidably generate a certain amount of wastewater as part of the filtration process. For many systems, this is 4 parts wastewater to one part filtered water (permeate).

This ratio can be reduced from 4:1 to 1:1 or even lower by using a pump to increase efficiency.

Filter Replacements

Pre-filters, post-filters, and the RO membrane all require periodic replacement for the system to operate efficiently. Generally, these replacements are fairly inexpensive, and will still cost significantly less than buying filtered water.

Space Requirements

You’ll need a certain amount of free space under your sink or on your countertop to install a reverse osmosis system. If you don’t have the necessary space, you can also install the system in an adjacent cabinet less than 10 feet from the sink.

RO Faucet

Under sink units require a separate faucet on your sink or countertop. This may require drilling through the sink or countertop – which can be a bit of a pain.

Drain Hookup

A drain hookup is needed to dispose of wastewater generated by the RO membrane. This will require drilling into the drain pipe under your sink to attach the drain line.

What Is RO Water Filtration and How Does It Work?

Reverse osmosis water filtration is a water treatment process that uses pressure to force water through a semi-permeable membrane. At this point, the water is separated into two streams, one with contaminant-filled wastewater and the other with clean filtered water. The wastewater is then flushed down the drain, while the filtered water passes on to the rest of the system.

Reverse osmosis requires water pressure to operate, as water does not naturally flow from a stronger saline solution to a weaker one. The process is essentially osmosis in reverse, and without energy in the form of water pressure, no filtration could take place.

What Water Contaminants Does Reverse Osmosis Remove?

Thanks to the effectiveness of its membrane, reverse osmosis systems are capable of removing an impressive range of contaminants from water. When you include the pre and post-filters, you’ll get an even broader level of contaminant removal.

RO systems will remove the following:

  • Sand, silt, dirt, and rust
  • Chlorine and chloramine
  • Disinfection byproducts
  • Herbicides and pesticides
  • VOCs
  • Heavy metals including lead, arsenic, mercury, chromium, and copper
  • Minerals and salts
  • Asbestos
  • Radioactive elements
  • And more


Reverse osmosis systems span a range of price points, starting at just $100 or so for a basic countertop unit, and up to $10,000+ for a whole house setup with all the bells and whistles.

Countertop RO systems are the least expensive type – generally costing between $100 and $500. These units sit on your countertop and only require a simple kitchen sink hookup for installation.

The next up in terms of price is under sink systems. These units must be installed under a kitchen sink and require a more complicated installation including a drain line hookup and a faucet installation. Under sink units mostly range between $150 and $600, but if you plan to hire a professional to complete the installation you’ll need to factor in a couple hundred more.

plumber installing reverse osmosis system under sink

Lastly, whole house RO systems are the most expensive type – ranging anywhere from $500 up to $10,000+. Whole house systems, as their name suggests, filter all of the water coming into your home, and must have significantly larger filter capacities than countertop or under sink units.

When considering the cost of a system, it’s important to include the cost of filter and membrane replacements in your calculation. Generally, pre and post-filters must be changed every 6 to 12 months, while membranes last between 2 and 5 years.

As far as filter replacement costs go, countertop/under sink systems will run you between $60 and $200 annually, while whole house systems will cost between $200 and $1,000 annually.

If you have any thoughts about the question, do I need RO, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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