How A Reverse Osmosis Drinking Water System Works

15 May 2020
 Categories: Home & Garden, Blog


Osmosis is a process in which molecules pass through a semi-permeable membrane. They travel from a less-concentrated to a more-concentrated solution. For purposes of drinking water systems, the process is reversed. The result is purified drinking water. Keep reading for how the reverse osmosis process provides healthy drinking water.


With a water filtration system, the first step is pre-filtration. The cartridge typically consists of carbon and sediment filters. The first cartridge's job is to remove larger sediment, including dissolved solids as well as chlorine. The purpose of the pre-filtration cartridge is to prevent those items from reaching the reverse osmosis membrane and damaging it.

Reverse osmosis filtration works best when you start with good water, which the membrane then transforms into purified water. Therefore, this step of filtration may not be necessary if you're starting with tap water rather than well water.

Reverse Osmosis Membrane

The main step of the filtration process involves the reverse osmosis membrane. The membrane typically consists of a thin polyamide layer on top of a porous layer. A non-woven fabric supports the membrane. The membrane is semi-permeable, meaning it's constructed so that water molecules can pass through while contaminants cannot.

A pump forces the water through the pre-filtration cartridge to the reverse osmosis cartridge. According to the CDC, the internal membrane can remove bacteria, viruses, and common chemical contaminants. These contaminants include metal ions and aqueous salts. The water that comes out the other side is free of contaminants such as lead, arsenic, radium, and fluoride.

Post Filtration

After passing through the reverse osmosis cartridge, the water is forced into the post filtration cartridge. Inside is a carbon filter. The carbon filter's job is to remove any trace elements of chlorine, any particles, and also volatile organic compounds. It works by adsorption, which is the process of attracting certain elements to the carbon's surface.

Post filtration is mostly a fail-safe to the reverse osmosis procedure in case any contaminant molecules get through. However, the carbon filter also removes tastes and odors from the water, which makes it more palatable.

Final Polish

The final step of a drinking water filtration system is mostly reserved for homes that use well water. When the well pump sends water through the first three stages of the filtration system, the water comes to rest in a holding tank until you're ready to use it. The storage tanks are usually metal, plastic, or fiberglass.

The storage tank may impart some odor or flavor to the water it holds. The final polish cartridge consists of another carbon filter. This cartridge removes any odor or flavor from the water before it comes out of your tap.

Use a filtration system to provide healthy, delicious tap water. And contact a company like Oxley Softwater Co to learn more.