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How Does a 4-Stage Reverse Osmosis Water Filtration System Work?

You may, or may not have heard of reverse osmosis water filtration systems. These thorough water purification systems do a better job than any of eliminating particles of minerals such as iron, manganese, lead, and sulfates from your water.

Eliminating these minerals from your water offers a number of different benefits, including greater water purity and an endless supply of high-quality drinking water. But maybe you’re skeptical of the effectiveness of a reverse osmosis system. Maybe you’d like to see how the system works. Well, this article has got you covered. Here is how a 4-stage reverse osmosis water filtration works.

Components of a 4-Stage Reverse Osmosis Water Filtration System


The housing of a reverse osmosis system is the external structure that holds all of its components together.

Feed Valve

Connecting to the water main, the feed valve is the component which injects water into reverse osmosis system.


These filters are used to remove large contaminants such as dust, dirt, and similar debris.

Reverse Osmosis Membrane

This is the primary component of the reverse osmosis system. It removes any dissolved minerals which are existing in the water by flushing them out of the system.


Post-filters exist simply to filter out anything that the pre-filters and reverse osmosis membrane missed.

Storage Tank

This is the tank that holds water which has been purified and which is ready for drinking.

Automatic Shutoff Valve

This valve is automatically activated when the storage tank is full. It prevents the water main from injecting any more water into the reverse osmosis system, conserving water and saving energy.

Drain Valve

This valve is used to dump out any water which is still contaminated with minerals.


The vast majority of reverse osmosis water systems make use of their own faucets. You can use this faucet whenever you want clean, purified drinking water.

Filtering Stages

Sediment Pre-Filter

The first stage of the 4-stage reverse osmosis water filtration system involves a sediment pre-filter. This pre-filter filters out the most basic of water contaminants, including dirt, dust, and other large, obvious debris.
This pre-filter is especially necessary for those who get their water from a well or a spring. Water which comes from these sources is almost guaranteed to be contaminated with at least small traces of dirt or sand.

Carbon Pre-Filter

The next step in a 4-stage reverse osmosis filtration system involves a carbon pre-filter. Eliminating several components from the water, including lead as well as tastes and odors that stem from the presence of chlorine, this stage serve to neutralize the water so that it tastes pure and free of chemicals.

Reverse Osmosis Membrane

The key stage in a 4-stage reverse osmosis water filtration system involves a reverse osmosis membrane. This membrane is capable of eliminating 95% of all dissolved solids from your water, softening it and giving it as smooth a consistency as possible. After water has passed through this membrane, it will be almost completely free of contaminants.

Post Carbon Filter

The last stage of a 4-stage reverse osmosis system makes use of a post carbon filter. This filter is the last line of defense against any contaminants that might still be passing through your water after the first 3 steps of the process.
Known as the “polishing” filter, it remains any additional taste that may remain as a result of chlorine, lead, or iron. After this step has been completed, your water will be purified and ready for drinking.

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