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Reverse Osmosis (RO) FAQs

Quickly find answers to some of our most-asked questions below.




What is Reverse Osmosis (RO)?

The simplest definition for Reverse Osmosis (RO) is that it’s a process that treats and reduces harmful contaminants found in drinking water.


How does Reversed Osmosis (RO) work?

As its name implies, RO takes osmosis, a natural process that occurs in every cell-based organism—plants, animals and even people—and reverses it.

During regular osmosis, a diluted solution passes through a semipermeable membrane and flows into a more concentrated one. A good example of osmosis is when your fingers become “prune-y” after swimming in the ocean. Through osmosis, the water in our bodies passes through our skin, out to the water around us.

In osmosis, the semipermeable membrane acts like a mesh screen with holes large enough for small molecules, like water, to pass through. Water molecules are small because they’re made of just three atoms: two hydrogens and one oxygen. But, there are a lot more atoms in a molecule of salt water, making them a lot larger.

Unlike regular osmosis, that happens naturally, Reverse Osmosis (RO) requires an external force (pressure) to work. Pressure is a key part of the RO process because separates contaminant molecules from water molecules and pushes it through the semipermeable membrane. Just like in regular osmosis, the membrane allows water to flow through—but blocks out larger molecules, like contaminants.

In other words, when more pressure is applied to contaminated water in Reverse Osmosis (RO), the more effective the process becomes.

How does a Reverse Osmosis (RO) System work?

RO systems vary depending on brand and design, but in general, they perform the following functions: pre-filtration, reverse osmosis, drainage and storage.

The system connects to drinking water lines and uses a high-pressure pump to propel feed water through. Feed water passes through a series of filters, usually carbon-based, designed to “catch” sediment and mineral deposits before flowing into the reverse osmosis chamber. Here, the feed water is pushed through the semipermeable membrane.

Think of the membrane as a tightly woven piece of fabric—one that looks virtually impermeable to the naked eye. To give you an idea of how stringent the membrane is, the diameter of a strand of human hair is roughly 100 microns wide. But, in Culligan RO Systems, the spaces in the membrane are approximately ONE micron wide.

The system drains out all contaminants not caught in filters at each stage, and treated water is stored in a small tank until use.

What are common contaminants removed by Reverse Osmosis (RO)?

A high performing RO system can remove up to 99% of dissolved contaminants found in feed water.

  • Salts

  • Particles

  • Colloids: oil and fat-based molecules

  • Organic bacteria

Pyrogens: protein-based substances produced by bacteria that cause fevers when introduced into the human body

Culligan Satisfaction Guarantee

If you are dissatisfied with your Culligan product for any reason within 30 days of your purchase, Culligan will remove the product and refund the purchase price.

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