Rogelio Alvarez

By: Rogelio Alvarez on May 30th, 2023

Print/Save as PDF

What Is a Reverse Osmosis System?

Water Filtration & Purification

Carrying bottled water cases each time you run out of drinking water is tiresome. Luckily, there is a way to enjoy superior-quality drinking water without going to the store. A reverse osmosis (RO) water system is an ideal solution to having crisper drinking water in your home, but what is it?

At Monkey Wrench Plumbing, Heating & Air, we’re trained and experienced in installing RO systems and understanding how they work. For over 15 years, we’ve been helping homeowners obtain purified and better-tasting drinking water from the comfort of their houses. 

We’ll break down how reverse osmosis uses multi-filtration to improve the quality of water for you to drink and use in coffee, tea, and cooking. At the end of this article, you’ll understand how reverse osmosis systems work so you can decide if this water filter is a dependable fit for your home. Let’s jump right in.


How Does a Reverse Osmosis System Work?

A reverse osmosis system is a water filtration method that helps improve drinking water quality, among other benefits. It is usually installed at a single faucet, such as a kitchen sink, or it’s also available as a whole-house system that provides filtered water throughout a home.

The system contains multiple filters, such as a sediment filter, carbon filter, semi-permeable membrane, and a postfilter. Each filter has a micron rating, a measurement used to determine the amount and size of particles and contaminants removed from liquids. 

Most people in Los Angeles may seek drinking water from other sources without being aware that the tap water in their homes is already considered drinkable by the Environmental Protection Agency (EPA). Although safe to drink, tap water still contains contaminants but not enough to be regarded as a public health risk. 

A RO system can remove the following water contaminants.

  • Bacteria
  • Viruses 
  • Arsenic

  • Volatile organic compounds (VOCs)
  • Physical particles 

Thanks to the reverse osmosis water system’s design, it can provide water that is 99% free of contaminants. 

Now, let’s start looking at each filter to get a clear sense of how RO systems work. One of the first filtration segments in a RO system is the sediment filter, but what does it do?


Sediment Prefilter

A sediment filter helps prevent physical particles such as sand, clay, dirt, and other organic material from remaining in drinking water. Water naturally picks up this organic material as it passes through natural sources, such as rocks. 

Although most public water systems filter the larger minerals out, tiny particles of these contaminants may still be present in tap water. Sediment filters play a key role in getting rid of these smaller contaminants. Sediment filters usually have a micron rating of 1, 5, 10, or 20. This allows the filters to capture very tiny dirt particles. 

When it comes to multi-filtration water systems, sediment filters are usually where water travels through first. Any physical particles not filtered out first are more likely to get caught in other filters and cause them to be less effective at filtering. This applies directly to the next filter in a reverse osmosis system, the carbon filter. 


Carbon Prefilter

The carbon filter is the next stage water will continue the reverse osmosis process. This filter is designed to decontaminate water further by filtering out chemicals such as chlorine. Safe amounts of chlorine are added to public water systems to help kill bacteria found in water.

Like metal filings to a magnet, carbon filters use a similar process called adsorption to attract VOCs such as pesticides, solvents, nitrates, and more. Carbon filtration helps improve the taste and odor of water, making it necessary to have it within a reverse osmosis system. 

Carbon filters can also come in different forms, like whole-house alternatives or even dual-stage carbon filters in RO systems. The effectiveness and benefits of carbon filtration can be scaled up by opting for a whole-house system. Some reverse osmosis systems have two carbon prefilters to help provide double filtration for drinking water. 

Once the water has passed through carbon filtration, it will go through the process from which RO systems get their name, reverse osmosis. 


Semi-Permeable Membrane

The actual process of reverse osmosis occurs in the semi-permeable membrane of an RO system. Water is forced through the membrane, and the membrane catches any contaminants. 

The semi-permeable membrane has a micron rating of .0001, making it highly effective at catching any contaminants remaining from the first filtration stages. It can prevent around 95% to 99% of dissolved solids from passing through the water. 

Once it passes through the membrane, water is already highly filtered, but some reverse osmosis systems have a post-filtration stage to decontaminate the water further. 



The post filter is a carbon filter ensuring the water quality remains crisp. It helps preserve the taste of water and remove any possible lingering odors. 

The post-carbon filtration will help remove any residual taste and chemicals. Despite having several filters, reverse osmosis happens instantaneously without delaying the water flow.

At this point, most RO water systems provide clean and crisp drinking water, but some offer extra filtration stages to further improve the drinking water quality.


Extra Filtration Stages (Optional)

Some reverse osmosis water filtration systems include additional filtration stages. Some may consist of an extra carbon post filter or an ionizer. 

A water ionizer affects the pH level of water to create alkaline water. Alkaline water may positively impact a person’s health, but the results are debated. These additional filtration stages are optional and not included in every reverse osmosis system. 


Is a Reverse Osmosis System Right for Me?

Plastic water bottles can accumulate on countertops and sometimes left abandoned half-drunk. RO water systems can help eliminate the need for plastic bottles while providing crisp drinking water. Now that you know how reverse osmosis systems work, you can be more confident when deciding if this system suits your home. 

Since 2007, we’ve been installing and helping homeowners understand how RO systems work. At Monkey Wrench Plumbing, Heating & Air, we’re passionate about giving Los Angeles homeowners and their families the best drinking water possible so they’ll never have to worry about what’s in their water.

If you have any questions regarding reverse osmosis systems, schedule an appointment through our water filtration scheduler or contact us using one of the buttons below. 

If reverse osmosis systems sound enticing, looking into what factors affect their pricing is recommended to help you prepare and decide on whether an RO system suits your home.