What Is Reverse Osmosis, and How Does It Work?

Close-up of water flowing

If your family has shunned tap water for bottled water, you’re not alone. Many people avoid drinking from their home water supply due to flavor issues or concerns about what’s in the water. Yet, there are plenty of affordable and highly reliable filtration options for the house that allow you to get great-tasting and safe water. Switching from bottled water to filtered tap water not only saves you money but also reduces the trash going into landfills. Reverse osmosis filtration is one of the most advanced options for purifying drinking water at home. Discover why it’s such a highly effective filtration method and how it could encourage your family to drink more affordable tap water.

What Does Reverse Osmosis Remove from Tap Water?

Hand holding a glass filling it up with water from the kitchen sink faucent

Like most water filtration methods, reverse osmosis can remove specific contaminants from water suspected or known to cause health problems. RO removes more contaminants than other filtration methods, including:

  • Chlorine, which is used for sanitizing tap water in most cities
  • Detergent
  • Bits of dirt and other physical contaminants
  • Organic compounds that cause odors or flavors
  • Dissolved minerals
  • Salt
  • Heavy metals
  • Fluoride
  • Bacteria and viruses

The Basic Process of Reverse Osmosis

A diagram of how reverse osmosis works

So how does reverse osmosis manage to remove such small particles and contaminants in drinking water? The secret is a membrane that has a very fine pore size. When water moves through this membrane, it traps the unwanted particles, ensuring only the purest water comes out of the faucet. Most home water filtration systems utilizing RO also rely on carbon pre-filters and post-filters to trap larger particles like dirt and rust to keep them from clogging the surface of the membrane. There’s a reject stream attached to a drain connection to flush the impurities away. You’re left with only fresh and clean water coming out of the faucets attached to the filter system.

Fine Filtration at the Micron Level

A close-up of small air bubbles in water

The key to reverse osmosis is that the membranes have pores as small as 0.0001 microns. To understand what that means, consider that a human strand of hair is about 70 microns wide. Each pore in the RO membrane is so small that almost nothing but pure water can flow through. This alone is surprisingly effective at providing fresh-tasting, odor-free drinking water regardless of the supply. Even salts and dissolved minerals are removed with this method, reducing the need for separate water softening. That’s one of the reasons that RO is used as a primary treatment for drinking water on a commercial scale.

Benefits of RO Filtration for Drinking Water

Water bottles

When installed properly, an RO system can remove up to 99.9% of all contaminants in a tap water supply. That’s the most significant benefit to most homeowners trying to break the bottled water habit. Lead, E. coli, and hard water are no longer an issue once you upgrade to a high-quality RO filtration system. Even odor and flavor issues disappear, which is not always the case with other types of treatment. Finally, these systems can be inexpensive to maintain over time, even when they cost more upfront than other methods to install.

Remineralization Options

Little girl smiling holding a glass of water

Since reverse osmosis is such a powerful technique for removing everything from your tap water, it tends to leave the water flavorless. If you’re used to the flavor of slightly mineralized water, remineralization is always an option. Remineralization involves moving the water through an additional chamber, which is added onto the filter system after the final post-filter to help introduce small amounts of minerals back into the water. A little calcium and salt improve the flavor and hydration value.

Reverse Osmosis vs. Other Water Filtration Methods

No other water filtration method available for home use offers as fine a point of filtration as reverse osmosis. While RO removes up to 99.9% of contaminants, activated charcoal or other materials are far less effective. For example, charcoal can only filter out particles of 1 micron or larger. With an RO membrane handling particles many times smaller, it’s clear that it provides a superior water filtration result.

A complete house RO system is quite an investment. Try starting small with a unit that only filters the water for a single faucet that can be designated as the drinking water supply for the house. This reduces maintenance over time by skipping the filtration for appliances and showers where it’s less needed.

While do-it-yourself projects can be fun and fulfilling, there is always a potential for personal injury or property damage. We strongly suggest that any project beyond your abilities be left to licensed professionals such as electricians, plumbers, and carpenters. Any action you take upon the information on this website is strictly at your own risk, and we assume no responsibility or liability for the contents of this article.