Is a Whole House Reverse Osmosis System Necessary?

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Reverse osmosis systems as whole house water filtration systems are not common, and for good reason.

Unless you have highly contaminated water, it just is not necessary. In the majority of cases, a whole house RO system is overkill.

However, some homes need it. Let’s see if yours is one of them.

Key Takeaways

  • Whole house reverse osmosis systems are necessary for homes with severely contaminated feed water, usually those in rural areas with wells.
  • A whole house reverse osmosis system is seldom necessary for most homes with treated municipal water.
  • It is essential to understand the chemistry of your water so that you can determine what kind of filtration is necessary for you, whether that be RO or something else entirely.

Is a Whole House Reverse Osmosis System Necessary?

So, is a whole house reverse osmosis system necessary?

A whole house reverse osmosis system is recommended only for homes that have highly contaminated water, and they are often found in houses in rural areas with well water.

Most homes, however, are okay with a more straightforward and less costly point-of-use or point-of-entry water filter system.

Also, municipal water is chlorinated to kill pathogens and is unlikely to contain dangerous contaminant levels that only a whole house RO system can eliminate.

If you are concerned about the contaminant levels in your water, get it tested to see if it is worth going to the effort of installing and maintaining a whole house reverse osmosis system. This is particularly important if your home is near manufacturing plants, areas with a high agricultural output, or if you have well water.

RO systems can remove most contaminants from a water supply, including arsenic, lead, and nitrates. Severe levels of these in your water supply can be harmful, which is when a whole house reverse osmosis system should be considered.

When Do I Need a Whole House Reverse Osmosis System?

The condition of your water will be the determining factor in choosing a whole house reverse osmosis system. Many harmful pollutants in your water are odorless, tasteless, and colorless, so you will have to perform water testing to see if any exist in your water at unsafe levels.

Thorough testing will tell you what chemicals, metals, and organic compounds are in your water supply.

If the water tests show higher than safe levels of arsenic, lead, chromium, TDS, nitrates, and nitrites, then you may need a whole house RO filtration system with the relevant pre and post-filters. Elevated levels of these chemicals can cause health issues, and not many filtration methods can get rid of them all in one hit.

If your water is high in specific singular contaminants such as chlorine, for example, there may be other options for whole house filtration for that that are much simpler.

How You Can Test Your Water

Water Testing Report

For well water, a sample should be collected and sent to a nationally certified laboratory. Here, it will be tested to the same standards as bottled and municipal water, and the report will be sent back to you within two weeks.

If contaminants in your water exceed the EPA’s safe level, they will be flagged in the report. As private wells are completely owner dependent when it comes to testing, you need to test regularly.

Municipal water is a different story, it is tested by the city, and the results are usually posted online, for example on the Environmental Working Group database.

What Is a Whole House Reverse Osmosis System?

A whole house reverse osmosis system is installed at the point where water comes in to supply your entire house. It means that every bit of water used in the household, from toilets to ice machines, is being provided with contaminant-free water.

It differs from a point-of-use system, which is usually hooked up to the kitchen faucet for contaminant removal from drinking and cooking water.

Aside from various pre and post-filters, RO water has traveled through a semipermeable membrane, which blocks contaminants from filtering through with the clean water. This leaves you with almost 100% pure H2O.

Whole House Reverse Osmosis System Components

It isn’t just the semipermeable membrane in a reverse osmosis system that makes it so effective at contaminant removal. In fact, if it were just an RO membrane in the system, it would not be practical for long, as the membrane is easily fouled and damaged by certain components in water, such as chlorine.

A good quality whole house RO system will have filters before the RO membrane and components after. They also have storage tanks to ensure you get the cleanest water delivered to your home without running out.

Usually, the components of a whole house RO system are:

  1. A pre-filter rated at 5 microns for silt, sand, and sediment reduction.
  2. A carbon pre-filter for removal of chlorine and other chemicals.
  3. If needed: A water softener may be used to lower water hardness. Iron filters remove excess levels of iron, manganese, and sulfur.
  4. A reverse osmosis membrane for separating most leftover contaminants from the water.
  5. Remineralization and pH neutralization post-filters.
  6. Storage tank for the purified water.
  7. Delivery pump for adequate water pressure.
  8. Ultraviolet (UV) disinfection to kill any bacteria still in the water.

Considerations Before Investing in Whole House RO Water Purification

There are a lot of things to consider before you look at investing in a whole house RO system. They need careful planning, ongoing maintenance, and take up a whole lot of space. Factor in the considerable setup cost, and you want to ensure you are doing it right.

System Sizing

The system must have enough water storage capacity and filtration output to meet the demands of your household, particularly at peak times of water use.

Select a system with a high enough gallon-per-minute output for everyone’s individual water use and a storage tank that can keep up with expected water demand. RO is a prolonged process, so you don’t want to use up all the water and then wait 8 hours for the tank to fill up again.

A 1000 GPD system could produce around 40 gallons of water in an hour, filling a 250-gallon storage tank in about 6 hours. If your RO output is too low to meet your water demand, the system will constantly be running, and you will constantly be running out of water.


Whole house reverse osmosis systems rarely operate alone. If your water is so contaminated, you will likely need pre-treatment to avoid damaging the RO system.

Hard water can drastically shorten the lifespan of an RO membrane, so systems facing hard water will need water softeners installed before them. Most will also need sediment and carbon pre-filters to eliminate sediments and chemicals like chlorine that could foul the RO membrane.

It is imperative to understand the makeup of your water to determine what pre-treatment it needs.

whole house water filter cartridges of different sizes


RO water often sits at a pH of around 5-6, which is slightly on the acidic side.

Post RO filtration, a pH adjuster is usually installed to neutralize the acidic water, so it does not corrode your pipes.

Many will also require UV water purification to eliminate harmful microorganisms that could still be present in the water supply or that have grown in the storage tank.

Space Requirements

Whole house RO systems are large, and the storage tank alone could be taller than 6 feet. Pre-filtration and post-filtration steps, plus the water pump(s), also take up considerable space.

They cannot be installed outside, so you will need indoor space, such as a basement or spare room, to house the equipment. The area should also be roomy enough to easily maneuver around the RO system when performing maintenance.


While some systems waste as little as 1 gallon of water for every 5 gallons filtered, other systems are not so economical. Unfortunately, running an RO system without producing wastewater is impossible, which can add significant costs to your water bill.

Speaking of…


The smallest whole house reverse osmosis system will easily cost $3,000-5,000, and that does not include pre-treatment, post-treatment, and installation. Factor all of those in, and the cost can easily reach $10,000.

The various filters and membranes will need regular replacement, as well, as will the UV lamps if you have a UV post-purification step.

Needless to say, systems with a greater gallon-per-day output and a larger storage tank will be more expensive in both the initial setup cost and ongoing running costs.

5 Reasons Why Whole House Reverse Osmosis Might Not Be Right for You

Purchase, Installation & Maintenance Cost

Whole house reverse osmosis is expensive to set up and install and costs a lot to maintain. Depending on your pre and post-filtration steps, and the level of contamination of your source water, yearly replacement costs of filters could be very high.

Maintenance Work

Unlike point-of-use systems, whole house reverse osmosis systems require significant maintenance. If that isn’t something you think you can do alone, you will need a technician to maintain the system or perform repairs if anything goes wrong.

Requires Work If Done Yourself

If you do feel up for installing and maintaining the system yourself, it will take a lot of time and effort, and it needs to be done correctly, or the system won’t filter effectively and could cause damage to your plumbing.

Water Bills

There is no RO system that does not produce wastewater. A whole house system will add significant cost to your water bills, as you will be using the same amount of water daily, but gallons of the contaminated water are being flushed as you do so.

Over the Top Filtration

It is important to consider if this type of water filtration is necessary for you. Do you really need RO water to flush your toilet or take a shower? Is your source water highly contaminated? If not, then a point-of-use or a different kind of point-of-entry system may be a better option.


RO systems are not eco-friendly. For every 5 gallons of water produced, you will lose a minimum of 1 gallon of water which will be flushed as waste. With growing water shortages, this may be a concern.

What to Use Instead?

This depends on the condition of your source water. Some may be so contaminated that a whole house RO system with pre and post-filtration is needed.

However, this is only the case for some homes. If your supply has high levels of specific contaminants, you may be able to filter them using other means.

Reverse Osmosis at the Point of Use

If your water supply is considered safe for showering and other uses, you may just want a point-of-use reverse osmosis filter system to purify your drinking water.

Carbon Filtration

Carbon filtration may be an option if your water smells and tastes strange or is highly chlorinated. These filters will eliminate chlorine and other chemicals from your water supply.

UV Disinfection

UV disinfection may be a better option if your water is high in bacteria, viruses, cysts, and algae. This is the gold standard for water disinfection, eliminating some nasties that not even chlorine is capable of.

Water Softener

If your water is considered safe, but it is hard water, then a water softening treatment may be enough. Water softeners are much cheaper and easier to install and maintain than a whole house RO system.

salt-based water softener

What If I Still Want a Whole House RO System?

Some people, even with a municipal water supply that is considered generally safe, still want the peace of mind that a whole house RO system brings.

In this case, no harm done aside from costs and maintenance. If those things are not a deal breaker for you, do what makes you happy!

If you have any thoughts about the question, is a whole house reverse osmosis system necessary, please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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