What is Reverse Osmosis and How Does it Work?

What is Reverse Osmosis?

Reverse osmosis (RO) is an advanced water treatment process that purifies water by forcing it through a semi-permeable membrane designed to remove contaminants at a microscopic level. As water is pushed through this membrane under pressure, only pure water molecules are allowed to pass through, while dissolved solids, heavy metals, chemicals, bacteria, and other impurities are blocked and flushed away. Typically used in multi-stage filtration systems, reverse osmosis also includes pre-filters and post-filters to remove sediment, chlorine, and improve taste. The result is highly purified, clean, and great-tasting water, making reverse osmosis one of the most effective and reliable methods for improving drinking water quality in residential and commercial settings.

How does RO work?

The reverse osmosis process uses a semi-permeable membrane to separate water from contaminants. “Semi-permeable” means that some things can pass through and others can’t. A familiar example would be your furnace’s air filter. A key difference in semi-permeable membranes for water treatment is that they allow passage based on the size of the particle and its molecular charge.

Typical air filters separate the contaminants exclusively by size. Holes, or pores, in the RO membrane are just big enough for the passage of a water molecule. Even small particles such as tobacco smoke or paint pigments are too big to flow through an RO membrane. At this point, because the membrane only lets certain molecules pass through, there is some waste. The waste, a highly concentrated solution of contaminants, is sent to the drain. You are left with virtually contaminant-free, clean water that makes it through the membrane. This is called a permeate stream, or as we like to say, great-tasting, filtered water.

Reverse osmosis technology relies on pressure to push the water molecules through the membrane. Water pressure varies by water source. City water is supplied between 40 and 100 psi (pounds per square inch). Well water is delivered between 20 and 60 psi, depending on your pump. The production rate of the reverse osmosis membrane is dependent on factors such as temperature, pressure and Total Dissolved Solids (TDS) levels. Since reverse osmosis works slowly, most RO systems include a storage tank that collects treated water. This feature is included so you can fill your glass or pitcher with clean water whenever you want it.

Because reverse osmosis water is so pure, it can pick up bad tastes and odors from the storage tank’s bladder or walls if it is stored for long periods of time. Running the water through a postfilter once it leaves the storage tank will remove residual tastes or odors before the water is dispensed.

Reverse osmosis (RO) is a multi-stage water filtration process that removes contaminants by forcing water through a semi-permeable membrane.

Here’s how it works step-by-step:

1. Pre-Filtration (Sediment Filter): Water first passes through a sediment filter that removes dirt, rust, and debris.
2. Carbon Filtration: Next, carbon filters remove chlorine, chemicals, and odors that can affect taste and damage the membrane.
3. Reverse Osmosis Membrane (The Core Step): Water is pushed under pressure through a microscopic membrane that: Allows only pure water molecules through; and Blocks dissolved contaminants like lead, PFAS, nitrates, and bacteria.
4. Waste Removal: The rejected contaminants are flushed away through a drain line.
5. Post-Filtration (Polishing Filter): The purified water passes through a final filter to improve taste and clarity.
6. Storage & Delivery: Clean water is stored in a tank (or delivered instantly in tankless systems) and is ready on demand.

What are the benefits of Culligan Reverse Osmosis?

• Advanced, Proven Filtration Technology
• Culligan systems are built around multi-stage filtration, often with up to 7 stages and multiple interchangeable filters, delivering deeper purification than basic filters.
• Removes up to 99% of impurities for safer drinking water
• Certified to reduce 60–90+ contaminants including lead, PFAS, bacteria, and microplastics
• Custom-Tailored to Your Water
• Systems can be customized to your local water conditions
• Options for remineralization (adds healthy minerals back)
• Multiple filter configurations for specific contaminants
• Smart Features & Modern Technology
• Smart monitoring systems (track usage, filter life, contaminants removed)
• Tankless options for space-saving design
• Filter-change indicator lights
• Low Maintenance & Long Filter Life
• Filters can last up to 1–2 years
• Designed for easy maintenance and reliability
• Optional service plans available
• Culligan Brand RO has better long-term value
• Better Long-Term Value
• Unlimited clean water at home (no bottled water costs)
• Systems that produce hundreds of gallons per day
• Long lifespan with professional support
• Culligan is a Trusted Brand that offers local Professional Support
• Third-party certified systems for performance and safety
• Professional installation and local service support
• Long-standing reputation in water treatment

Featured Reverse Osmosis Water Products

Aquasential® Reverse Osmosis Drinking Water Filtration System

Feel confident in your water quality with a reverse osmosis (RO) water system that’s certified to reduce 18 times more contaminants than the leading standard pitcher filter.¹ Get amazing water for your family while also reducing your carbon footprint by saving waste from single-use plastic bottles.

• Modern Configuration: Enjoy a sleek, contemporary look and space-saving design.
• Minimal Maintenance Required: Experience the benefits of having a 7-stage reverse osmosis system that’s tested against rigorous standards, built for longevity and has long-lasting warranties.
• Durable Filters: Choose one- or two-year filter life, which is notably longer than many other filtration options.
• Flexible Installation: Place your system anywhere in your home that has access to a cold water line.

Aquasential® Tankless Reverse Osmosis System

Savor an unlimited supply of filtered water with the Aquasential^® Tankless Reverse Osmosis (RO) Drinking Water Filtration System. This compact unit is equipped with innovative features that provide real-time water quality feedback and leak detection for even more peace of mind.

• Space-Saving Design: The elegant, compact architecture makes this system an effortless addition to your home — no matter the size of your space.
• No-Fuss Filtration: Our team of water experts thoughtfully crafted this tankless reverse osmosis system to include advanced filtration so you never have to think twice about your water quality.
• Four-Stage Filtration Process: Reduce dissolved solids and​ particulates for cleaner, safer tap water you can trust.
• 2-in-1 Sediment and Carbon Filter: Address materials — like dirt, sand, and rust for a more refreshing water experience.
• High-Capacity Solution: Tackle even more contaminants with a specialized, semipermeable membrane that provides comprehensive filtration.
• Carbon Block Filter: This final polishing stage targets any remaining bad tastes and odors so you can enjoy crisp, fresh-tasting water with every sip.

Aquasential® Smart Reverse Osmosis Drinking Water Filtration System

Meet the world’s most efficient reverse osmosis (RO) water system¹ — certified to reduce 18 times more contaminants than the leading standard pitcher filter.² With features like filter change alerts, water quality tracking and RO water with the touch of a button, enjoy peace of mind about your water quality.

• Peace-of-Mind Monitoring: It’s easy to stay on top of filter changes and service needs with notifications from your phone. Plus, worry less knowing your local Culligan team can monitor your system’s performance remotely.
• Wellness-Focused Features: Set water consumption goals and record your progress, with notifications to help you make sure you’re getting the hydration you need.
• Worry-Free Water Quality: Our smart water filter tracks the contaminants reduced in your water, so you can feel confident you’re getting water you can trust.
• Save Money (and the Planet): See money and plastic-waste savings from eliminating single-use bottles by using a water filter for your sink instead.
• Award-Winning Product: In 2022, our smart reverse osmosis water system was highly rated by experts at House Beautiful, winning a Live Better Award recognizing “innovative homewares that make life a breeze.”

CONTACT KARSARE WATER SYSTEMS

Reach out to us get a quote specific to your water needs for your home, business or industry.  When you take this step, you can have peace of mind about your health and your environmental footprint.