How Reverse Osmosis Works: An Overview of the Filtration Process

Reverse Osmosis System

When we drink water, we often don’t think about the process behind the scenes until we’re faced with the need to find the right solution for our water needs. There are many ways to purify water, like distillation, chlorination, or carbon filtration. One type of home filtration is reverse osmosis (RO), which produces purified water by casting away harmful particles. With this guide, we’ll walk you through the system of reverse osmosis and the filtration process — to help you determine if a reverse osmosis filtration system is the answer to your water purification needs.

How Reverse Osmosis Works


To understand how RO works, we need to discuss the process of osmosis, which is the key to all life’s functions inside the body and out. In osmosis, water molecules cross over a semipermeable membrane to reach a state called equilibrium.

This concept has a lot of scientific terminology, so we’ll make it simple. In its nature, water travels to where there is less of it. When there is a lower water concentration, there is a larger concentration of something else, like other particles and substances. Water essentially moves to these areas of less water so that both places end up having the same amount of water, hence “equilibrium.” In osmosis, this principle is shown as the water from a high concentration crosses through a semipermeable membrane (a porous sheet that allows only the small water molecules to pass through) into the area of low concentration.

Reverse osmosis

Now it’s time to reverse. Like its counterpart, the semipermeable membrane only lets small water molecules through. However, the key difference is that pressure is applied to the water, causing it to flow through the membrane to one side, leaving behind the other larger particles that did not fit through the pores. In this fashion, RO separates the water from the contaminants so it is pure and ready to drink.

If you find it hard to picture in your mind, think about sifting for gold. There are special pans with mesh on the bottom that you can dip into the water and sift for any trace of the precious metal from the water mass.  All the water collected with the dirt and sand quickly drips from the mesh from the pressure of gravity, leaving behind the rocks and larger particles for you to sift through in the pan. Like panning for gold, reverse osmosis uses a mesh-like membrane to separate what you want from what you don’t. Except in RO, your outcome is focused on the water dripping through the membrane instead of the collected sediment particles.

What harmful particles are removed by reverse osmosis?

It can be hard to believe that your water holds some hazardous elements, but a few toxins can exist in your water! Using a reverse osmosis system can help relieve your worries. Because of RO’s water-favoring membrane, you can say goodbye to traces of arsenic, chlorine, sodium, lead, PFAs, and even pharmaceuticals.

Why is this important?

Water is at the center of our lives. We drink it, cook with it, play with it — water is central to everything we know and love. However, if our tap water is contaminated with dangerous particles, our ways of life can be impacted negatively by severe illness and bodily issues like indigestion, dry skin, and even growth development. A fully functional filtration system like reverse osmosis can illuminate these health risks and open the door to a more confident way of life.

A Step-by-Step Process for Reverse Osmosis Filtration

There are many filtration systems out there, but the NH Tap Reverse Osmosis System can finish the water purification job in four steps.

Reverse Osmosis Stages:

  1. Sediment Pre-filter: This filter decreases the risk of contaminants clogging the RO membrane. It also aids in preventing the formation of a biofilm.
  2. Carbon Pre-filter: This filter removes contaminants by activating carbon molecules to attract the harmful particles and possibly begin a modification in their chemical compositions.
  3. Reverse Osmosis Membrane: When pressure is applied to the water, it is pushed through the RO membrane’s selective pores to separate it from the contaminants.
  4. Post Carbon Filter: To finish the process, this filter improves both the quality and taste of the filtered water.

The types of pre-filters and post-filters depend on the purpose intended for the product.

At NH Tap, we aim to provide you with the cleanest water and the best tasting.

Where does the water go after filtration?

After the water passes through the reverse osmosis membrane and is filtered once again, the water is stored in a water tank that fits perfectly underneath your sink.

Do I Need a Reverse Osmosis Filtration System?

If your water begins to taste odd or if you or a family member has become sick from the water, we recommend a water test offered by NH Tap. Your newly identified water quality would then inform what type of reverse osmosis system you would need to install.

For a more holistic water treatment plan for your home, NH Tap would advise the NH Tap Absolute (well water) or the NH Tap Mainframe (public water). Otherwise, if you only wish for water purification at one sink, the NH Tap’s reverse osmosis system would be installed in less space than the other two offerings would take (can be used in most rental properties).

Maintenance of Reverse Osmosis Filtration Systems

When the correct maintenance procedures occur, reverse osmosis systems can last over a decade. All it takes is special care to replace specific parts when necessary. Because each piece of your reverse osmosis system is important to the process, each piece must be in working condition.  Our recommended schedule  would be as follows —

  • Sediment Prefilter: every 6-12 months
  • Carbon Prefilter: every 6-12 months
  • Reverse Osmosis Membrane: every 24 months (two years)
  • Post Carbon Filter: every 6-12 months

While you can use this proposed schedule as a generalized structure, your rotation will depend on your household’s usage of the reverse osmosis system and your local water status.

Benefits of Reverse Osmosis in Your Home

Not only does reverse osmosis remove unwanted particles from your drinking water, but it also lowers the costs of buying bottled water for filtered water. Your environmental waste will be reduced because you buy fewer packs of plastic bottles. In addition to sustainability and financial flexibility, reverse osmosis systems can provide your home with water that tastes good while drinking and when used to cook or bake.


In New Hampshire, our water is often the cause of uncertainty regarding our family’s health and happiness. Reverse osmosis is a sustainable solution that not only purifies your tap water but also reduces plastic waste and costly expenditures of bottled water. At NH Tap, our mission is to provide the best filtration system for our customers because we value trust and stability in essential resources like water. In bringing reverse osmosis to the home, we can ensure everyone has access to the healthy drinking water they deserve. Schedule your water test today!

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