64oz.org may earn commission for purchases made through the links posted on this page.

Reverse Osmosis Water Filtration System Explained

by Carl Jensen

Plumber, Welder, Contractor

> 2 min read


Reverse Osmosis Water Filtration System Explained

Currently, you have two options for getting clean drinking water, either live someplace with pristine drinking water or clean the water that comes into your home. 

With applied pressure, reverse osmosis pushes water through a semipermeable surface, ridding it of contaminants. As a water filtration system, an RO system is incredibly efficient and healthy, stocking your holding tank with crystal clear drinking water.  

If you need a system to filter household water daily, a reverse osmosis filtration unit is an easy-to-install and low-maintenance system that saves you money in the long run and preserves water clarity and nutrients.

HERE ARE OTHER QUESTIONS THAT YOU MIGHT HAVE ABOUT WATER:

What is Reverse Osmosis?

In regular osmosis, water molecules move through a semipermeable material from a high concentration to a lower concentration to equalize the two halves. 

In reverse osmosis, pressure is applied to force the water molecules through the membrane, but contaminants are left on the former side. Larger contaminants, both chemical and botanical, are removed, leaving only clear, clean water. 

These systems fit conveniently under your sink for water filtration, are simple to install, and are fully automated, so you always have clean-tasting water at the twist of a faucet.

How Does Reverse Osmosis Clean Your Water?

The water that comes into your reverse osmosis water filtration system is called the feed water, and the clean water that comes out the other side is called the permeate, filtering into a holding tank. The leftover is called the waste or the brine. 

On a molecular level, water molecules that are pushed through the semipermeable membrane, stippled with microscopic pores. Larger elements like ions, chlorine, and particles can’t fit through the pores and are left behind.

Typically, water is sent to your house via pipes from a public facility like a water treatment plant. The water is filtered and treated at plants, but the multiple stages of pre-and post-filters in a reverse osmosis system are like a super-cleaning machine for your drinking water. 

Here are the three different types of filters used in a reverse osmosis filtration system:

  • Sediment filter: removes rust, dirt, and dust from the feed water. 
  • Carbon filter: Volatile Organic Compounds (VOCs) dissolve into water sources or air, and a good carbon filter gets rid of them from your water.
  • Semi-permeable membrane: Total Dissolved Solids (TDS) are minuscule inorganic and organic dissolved particles, and this membrane strips your drinking water of the TDSs.

There are several filtering stages in a RO system, including prefiltration, reverse osmosis, holding tank, and post-filtration.

  • Prefiltration: Usually, a carbon filter and a sediment filter complete this primary process, getting rid of any dust, dirt, debris, rust, or VOCs into the reverse osmosis process. 
  • Reverse osmosis: Applied pressures to force the water from the prefiltration to reverse osmosis. It pushes pre-filtered water through a polyamide film whose pores are too small to let in larger contaminants but are just big enough for water to pass through. 
  • Holding tank: Once the water gets through the film, the water is kept in the holding tank before its final filtration.
  • Post filtration: When you turn on the faucet, the water leaves the holding tank and goes through a final carbon post-filtration to remove any odors and remaining particles.

If you want the extra assurance of clean water, invest in a natural system like a RO filter to keep your water in pristine condition.


"Larger elements like ions, chlorine, and particles can’t fit through the pores and are left behind." 


What Contaminants Does RO Remove?

You can’t always see them, but you could be ingesting harmful, invisible contaminants if you’re not using a water filtration system. You need a filtration method like a RO system to ensure that you are consuming the best quality water possible.

Here are some of the many contaminants that a reverse osmosis system can get rid of, so you know you are drinking the healthiest water available:

Additionally, the filters in a RO system can help reduce, if not eradicate, the presence of:

  • Arsenic
  • Sulfate
  • Magnesium
  • Potassium
  • Nitrate
  • Radium

The CDC also recommends a RO system for its ability to eradicate bacteria, protozoa, and certain viruses.

What are the Cons of a RO System?

All the benefits of a reverse osmosis water filtration system may seem too good to be true, but there are some drawbacks to consider. RO systems are initially more expensive to install, and they require professional repairs if they malfunction or sustain damage, which they rarely do.

These systems often filter water slowly, so it's essential to ensure that the filtration system you’re looking at has an adequate holding tank that can sustain your household. If you have an extra-large family, you will need a sufficient holding tank with the capacity to meet all your drinking water needs daily. 

It is recommended that you purchase a tank that provides at least 1 gallon of drinking water per person per day, with a 10% margin to account for wastage and cooking water. For example, a four person household needs four gallons plus 0.4 gallons for a total holding tank capacity of 4.4 gallons. 

Other aspects include the amount of brine or wastewater that an RO system puts out, but there are ways you can reduce the amount. Adding a permeate pump to your system may make it work more efficiently, decreasing the amount of wastewater it produces. 

You can also use the wastewater from your RO system to water your garden or for a water feature. An automatic shutoff valve can also help your system maintain maximum efficiency.


The Bottom Line

Drinking water is critical for good health, flushing your system of toxins and hydrating your cells, but if you’re not filtering, you may be doing more harm than good. You need an all-natural approach to remove the contaminants from your water efficiently.

A reverse osmosis water filtration system removes anything harmful from your water, leaving behind plenty of great-tasting water with absolutely no additives. Install a convenient, under-the-sink model today to increase your home’s value, decrease your carbon impact, and improve your household’s health.

Carl Jensen

About the Author

Carl Jensen is a plumber with over 50 years of experience in the industry, as well as related jobs like underwater welding. He runs a successful plumbing practice in Tampa, Florida, and contributes his plumbing expertise to our DIY articles, and helps to fact check and consult on most of our other stuff to boot.