Whole House Reverse Osmosis Filter Systems: The Definitive Guide for Home Owners

The Definitive Guide to Whole House Reverse Osmosis Filter Systems

Are you concerned about the safety of your drinking water and looking for a filtration system?

Reverse osmosis is one of the most effective and efficient way to filter your home’s water. It removes up to 99% of contaminants, including lead, mercury, chlorine and fluoride.

This Definitive Guide to Whole House Reverse Osmosis Filter Systems will teach you everything you need to know about this process so that you can make an informed decision on which type of system is right for your home.

You’ll learn how reverse osmosis works as well as what features are important in a whole house RO filter system. We also cover installation requirements like where the unit should be located and how to properly size a system for your needs. You’ll also have the confidence that once your new RO system has been installed, you can keep it working efficiently throughout its lifetime.

Continue reading to learn all about whole house RO filtration systems.

Reverse Osmosis – What Is It

Reverse osmosis is a water filtration process that uses pressure to force water molecules through a semi-permeable membrane. This membrane allows only pure water to pass through while trapping contaminants like lead, mercury and chlorine.

RO systems are often used for drinking and cooking water but can also be installed as part of a whole-house filtration system.

Principle of operationHow does RO filtration work

The membrane is the component of a RO system that filters out contaminants. A RO membrane is constructed of a specialty plastic sheet that is spirally wrapped and enclosed in a pressure-rated tube or module.

The membrane is fabricated so that it has thousands of tiny holes, called pores, that filter out the impurities. Pure water molecules are small enough to fit through the membrane’s microscopic openings while contaminant particles, even when dissolved in water, are too big to slip through these same holes.

The reverse osmosis process works by applying pressure against incoming dirty water so that it can pass over and under the semi-permeable membrane. The pressure pushes the water through tiny holes in the RO membrane, straining out contaminants that are too big to fit through these openings.

Typically, this pressure comes from your home’s water pressure. A minimum pressure of 50 psi is required for a whole house reverse osmosis system. If the supply pressure is not adequate, a booster pump is required.

Pore size is critical to performance

The most important element of the RO filter is the pore size of the membrane. A design engineer specifies the diameter of these openings based on the contaminants to be removed. The key is to ensure the pore size is small enough to remove the contaminants, but not too small where it causes excessive pressure loss or fouling.

Most RO membranes used for residential applications have a pore size of 0.0001 microns (μ). To put this into perspective, a human hair is 17 μ in diameter. Most bacteria are 1 to 2 μ in diameter.

Contaminants that reverse osmosis can remove

Reverse osmosis is effective at removing a wide range of contaminants. This includes:

Do You Need a Whole House RO Filter

The need for whole house reverse osmosis filter systems has increased in recent years, and the market is now saturated with a wide variety of different types of these systems. It can be difficult to know which system is best for you.

RO filter configurations for your home

under sink RO system
Under-sink RO filter systems are a very popular way to provide clean drinking water.

You can choose from four different configurations and sizes. The difference depends on whether you need to treat all of the water you use or just the water your drink and cook with.

  1. Point-of-use system: this type of system is installed at the faucet in your kitchen or wherever you need water. POU RO systems treat only the drinking and cooking water that comes out through this specific tap — and sometimes also provide filtered cold water to your refrigerator.
  2. Countertop system: this type of system is similar to the point-of-use, but it’s larger and installed on a countertop. Countertop RO systems are ideal for renters or people who don’t want to deal with installing a permanent unit.
  3. Portable system: this type of system is a small, lightweight unit that you can take with you when you travel.
  4. Point-of-entry system: Whole-house RO filter systems are used when all of household’s tap water needs to be treated for drinking and cooking. They are usually installed at the main water pipe in your home, which is called a “point-of entry” (POE) system because it treats all of the household water as it enters through this point.

Check Pricing on Amazon

Type of contaminants

Generally, the decision to treat all of your water versus just your drinking water depends on the contaminants you need to treat. Some contaminants only need to be removed from your drinking water, and it doesn’t matter if they are in the water you use for showering and washing your clothes.

Examples of these impurities include lead, PFAS, and fluoride.

Some compounds are problematic regardless of what you use the water for. They have to be removed at the point-of-entry to avoid health risks or nuisances. Problems associated with contaminants that require whole house systems include:

  1. Odor: Contaminants that have a bad smell, like hydrogen sulfide, create problems everywhere you use your water. They have to be treated
  2. Toxic vapors: Volatile organic compounds (VOCs) can volatize (i.e., evaporate) when you shower or wash clothes and present a health risk. This includes most volatile organic compounds, gasoline, and solvents. These contaminants have to be removed from all water.
  3. Stain: Some compounds, like iron, have to be removed because they stain your plumbing fixtures and clothes.
  4. Scale and deposits: Some minerals, like calcium, create scale and leave deposits on your pipes and fixtures.

Your budget for reverse osmosis water filtration

Money is always a factor when it comes to home improvement decisions, and whole house reverse osmosis filter systems are no exception. Systems range in price from a few hundred dollars to several thousand, so it’s important that you select the one that fits your needs and budget.

Reverse osmosis water filter installation

Reverse osmosis water filtration systems have to be properly installed by a plumber or water treatment specialist to ensure they are functioning properly. Your water pressure, the number of filters in your system, and where the RO membrane is positioned all affect performance.

Space for reverse osmosis system

A whole house RO filter system is larger than an under-sink unit. You need to have adequate space for all of the components. In addition, you need enough room around the system so you can perform maintenance and repairs.

Important Components for a Whole House RO Filter System

Whole house system layout
Whole house RO systems often include pre-treatment filters, storage tanks, and booster pumps.

Before you purchase a reverse osmosis system for your house, it’s important to understand how it works and the components that make up a whole house RO filter system. Here is a list of the main components you’ll need for a system that can treat all of your household water:

  1. Particle filter: Filters out large particles, like rust, sand, and dirt.
  2. Carbon filter: Removes chlorine compounds from your water to protect the RO membrane from oxidation. It also reduces other contaminants like pharmaceuticals and VOCs.
  3. Post-carbon filter: Removes any bad taste or residual particles from the treated water to ensure it tastes and looks good.
  4. Water storage tank: Holds treated water for later use. In a pressurized system, this container stores the additional pressure required to push water through your home’s pipes and fixtures.
  5. Ultraviolet light disinfection: Kills microorganisms in the water to ensure it is safe for drinking. Although the RO filter removes pathogens, it is possible for bacteria to find their way to your storage tank and piping.
  6. Remineralization filter: Reverse osmosis removes essentially everything from your water, including the beneficial minerals. A remineralization adds minerals like calcium and magnesium into your water to improve the taste and quality.
  7. Booster pump: If your water supply pressure is low, you need a booster pump to increase the pressure.

Proper installation is essential for whole house reverse osmosis filter systems because all of these components interact. If one part doesn’t work correctly, your water will contain contaminants and be unsafe to drink or use in food preparation.

I wrote a detailed article explaining remineralization of RO water that you might find helpful.

Maintenance Requirements for Point-of-Entry RO Systems

Maintenance of RO system - filter replacement
Routine maintenance, especially filter replacement, is critical to effective water treatment.

Reverse osmosis filters require routine maintenance to keep everything working properly and to prevent premature failure of components. In general, all of the filters should be replaced regularly, and the membrane requires periodic cleaning.

  1. Filter replacement: Point-of-entry systems have larger filter cartridges than under sink ones that are more difficult to replace or clean. You can’t remove it from the system for regular maintenance like you would with an under-sink unit. These filters (sediment, carbon, post-carbon) need to be replaced every 6 to 12 months. Each manufacturer has its own maintenance schedule.
  2. Cleaning the RO membrane: The RO membrane is fragile and cleaning it incorrectly can damage it, so you need to contact your manufacturer for specific instructions. But generally speaking, if your system has a storage tank or pump pressure vessel, the membrane needs to be cleaned every six months or more frequently depending on usage levels.
  3. Membrane replacement: A good reverse osmosis membrane will last for many years – if it’s properly maintained. Eventually, you’ll need to replace it. The typical RO membrane requires replacement every five to ten years.
  4. Tank disinfection: The water storage tank should be disinfected annually with a bleach or other sanitizing solution. Check the owner’s manual for the manufacturer’s recommendations.
  5. Pump inspection and cleaning: The booster pump should be inspected and cleaned regularly, but the schedule will vary depending on use.

Point-of-entry systems don’t require as much maintenance as POU systems because they are larger and have a greater service life.

Designing Your Whole House Reverse Osmosis Water Filtration System

A good design will result in a reverse osmosis system that provides effective and efficient treatment of your water. If you are confident in your understanding of reverse osmosis systems, you can design your own system for your entire home. But if you’re not sure where to start, or would just like some professional help, a water treatment company can assist you.

Engineering parameters and your RO system

To properly design your whole house reverse osmosis system, there are several design parameters that must be determined. Start with the following information.

  1. Volume of water to be treated: The size of your RO system will depend on the volume of water your home uses each day. You can estimate this based on the number of bedrooms your home has. Assume 100 gallons per day per bedroom – a 4-bedroom house needs 400 gallons of water every day.
  2. Contaminants: Confirm that the contaminants you have can be removed using reverse osmosis. Some compounds require supplemental treatment or an independent treatment process.
  3. Flow requirements: In addition to the volume of water you need, you also need an adequate flow rate. Otherwise, you’ll be waiting a long time to fill your bathtub or may not have enough flow to shower.
  4. Plumbing size and configuration: Installing a reverse osmosis whole house system requires connecting it to your home’s piping. You need to know the size of your piping and whether it is accessible.
  5. Space: Whole house RO filters are larger than under-sink units. Make sure you have enough space to install the system and access it for maintenance.
  6. Water pressure: Your water pressure must be high enough to run the whole house reverse osmosis system. Most systems require a minimum of 40 psi, but some whole house reverse osmosis units need as much as 60 psi.

As you can see, designing a whole house reverse osmosis system is complicated. If you’re not up to the task, we recommend hiring a water treatment specialist.

Testing your water

Before you purchase and install a whole house reverse osmosis system, I recommend that you test your water. This will help you determine what is in your water. You should test for all suspected and known contaminants in your water. This includes things like lead, PFAS, pesticides/herbicides, etc.

You should also test for compounds that aren’t considered contaminants because some of them can cause fouling or maintenance problems. Examples of non-contaminants to test for include:

  • carbonate
  • iron
  • manganese
  • silica
  • suspended solids
  • dissolved solids

The best way to test your water is to have it analyzed by a laboratory. A state-certified laboratory is preferable to one that isn’t certified, but you aren’t required to use one for this purpose.

You can also do some preliminary testing yourself. Collect a water sample in a clean, clear container and take a look at it in bright light. This will give you an idea of the amount of suspended solids and turbidity in it.

Check out the TDS meter I use on Amazon.

You should leave the sample out for 24 hours and then inspect it again. You may notice that its color changed (orange/rust color indicates iron) or that a significant amount of solids have settled to the bottom.

Cost of Whole House RO Filtration System

A whole house reverse osmosis system is more costly than an under-sink unit. The price will depend on the size and features of the system. A whole house reverse osmosis system (equipment and installation) will cost around $8,000 to $18,000. Commercial systems are often installed in larger homes – these cost as much as $15,000 to $25,000 to install.

RO filter equipment cost for your entire home

The cost for a basic whole house unit is likely to cost between $500 and $1,500. This would not include any pre-treatment, water storage, or disinfection.

If you include all of the features and options listed above, the equipment cost may increase to as much as $2,000 to $4,500.

Purchasing quality components will push your budget to the high end of the range. A whole home reverse osmosis unit can be expensive, but they provide a lot of value.

Installation cost

Installation costs will also vary depending on your home’s plumbing configuration and whether any modifications are needed. You can expect to pay an additional $200 to $700 for installation of a basic system (no pre-treatment, water storage, or disinfection).

If you include all of the options in your system, the installation costs rise to $1,000 to $5,000. Much of these costs depend on the size of your house, your plumbing configuration, how much additional piping is required, and a lot of other factors. If your home requires additional piping or replacing copper lines with PEX, you can expect to pay substantially more for installation.

Even if you install the system yourself (DIY), you will need to purchase materials (pipe fittings, brackets, supports, etc.). These items may cost as much as $100 (for a simple installation) to several thousand dollars (if you need to add additional piping throughout your house).

Maintenance costs

The cost to maintain your whole house RO system will depend on the size of your system, the amount of pre-treatment you have, and the specific components you purchased.

  1. sediment pre-filter: these have to be replaced every 6 to 12 months and cost an average of $100 per filter.
  2. RO membrane: the membrane should last for many years. Most manufacturers recommend replacing them every 2 to 4 years. The average membrane cost for a POE system is $450.
  3. carbon filter: carbon filters should be replaced every 6 to 12 months. They cost an average of $180.
  4. carbon post-filter: carbon filters should be replaced every 6 to 12 months. They cost an average of $180.
  5. remineralization filter: Remineralization cartridges have to be replaced every 6 to 12 months. The average cost is $80.
  6. UV light disinfection: UV disinfection systems have to be cleaned every quarter. UV lamps have to be replaced annually and cost approximately $50.

Advantages and Disadvantages of Whole House RO Filters

Installing a whole house reverse osmosis system has many benefits, including:

  • improved water quality for the entire house
  • eliminates the need to buy bottled water or filters for individual faucets
  • increased home value (if you choose to sell your house)
  • saves money (compared to buying bottled water)

However, there are some disadvantages to consider before installing a whole house RO system:

  • initial cost is higher than an under-sink unit
  • installation is complicated and often expensive
  • wastes a lot of water
  • take up a lot of space
  • require continuous maintenance
  • aggressive water can corrode copper and other metal pipe and fixtures

A whole house water filter is a good investment for many homeowners. Many people with a whole-house reverse osmosis system are very pleased with their investment.

FAQs About Whole House Reverse Osmosis Filters

Is RO filtered water safe to drink?

The jury is still out. No studies have been conducted to demonstrate that drinking RO water is good or bad for you. The concerns cited by critics of reverse osmosis is that the water lacks beneficial minerals like calcium and magnesium.

If you are worried about the safety of your RO water, you can add a remineralizer to restore these minerals to your water. Drinking reverse osmosis water is good for you.

If I have a water softener, do I need a reverse osmosis filter?

A water softener is not the same thing as a reverse osmosis filter. They each treat your water, but they do different things. Using a water softener as pre-treatment for your RO filter will improve its operation and extend the life of your filter. Drinking reverse osmosis water is good for you.

How much does it cost to produce one gallon of water?

According to Home Advisor, it costs about $3.50 to treat 1,000 gallons with a reverse osmosis filter. This works out to about $0.004 per gallon (0.5 cents per gallon). Reverse osmosis filtration is much cheaper than bottled water and provides better water quality compared to activated carbon filtration.


Reverse osmosis is a water purification process that removes contaminants from drinking water. RO filters work by pushing contaminated water through membranes with tiny holes, which capture the impurities and force them to pass on into an outlet stream of clean, potable water.

The three most important things you should consider before purchasing your reverse osmosis system are how much treatment capacity you need, what type of pre-treatment is required, and how best to connect the equipment to your plumbing system. A drinking water reverse osmosis system provides a good value if you need a reliable water filtration system.

A whole house POE filter requires more than just installation. You also need to plan where everything goes so that everything fits in the space you have with plenty of access for maintenance and repairs.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

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