Difference Between Reverse Osmosis and Ultrafiltration

Although several water treatment technologies claim to purify water to perfection, none beats reverse osmosis and ultrafiltration systems.

The 2 systems are simply the most powerful and advanced. They eliminate all contaminants larger than their pore sizes to produce clean water.

Does this mean that the reverse osmosis and ultrafiltration are similar? Or is reverse osmosis better than ultrafiltration? Can ultrafiltration replace reverse osmosis?

Well, you’ll get answers to these questions and more after going through this detailed post on the differences between reverse osmosis and ultrafiltration.

FeatureReverse osmosisUltrafiltration
Membrane technologySemi-permeable membraneHollow fiber membrane
Contaminants removedDissolved minerals, salts, organic and inorganic chemicalsSolid particulate matter
StorageUses a storage tankNo storage tank
Waste waterWastes a lot of waterProduces no waste
Minimum operation pressure50 psiOperates effectively even under low pressure
Pore size0.0001 micron0.02 micron
InstallationA little difficult to installEase of installation depends on the unit. With a flushable membrane – complex installation. Without a flushable membrane – easy to install.
CostHigh upfront cost but cheap in the long runLow initial cost but expensive in the long run.

What is Reverse Osmosis?


 with Alkaline Remineralization


In simple terms, reverse osmosis is a technology that removes a vast majority of contaminants from water using pressure to force the water molecules through a semipermeable membrane.

It removes most dissolved minerals in the water, salts, and total dissolved solids (TDS).

  • Type of RO Membrane Technology

Reverse osmosis removes virtually everything from the water. An RO membrane is semipermeable with a pore size of approximately 0.0001 microns, making it the most effective water treatment method.

However, although pure RO water is tasteless as it is free of minerals and thus not a favorite to persons who like minerals in their water.

  • Contaminants Removed by Reverse Osmosis

If looking for drinking water with the highest degree of purity, you can never go wrong with reverse osmosis.

It gets rid of a majority of dissolved minerals like in your water, salts, and organic and inorganic chemicals in the water.

  • Storage

Reverse osmosis makes water slowly that you have to store it and make it available when you need it. That’s why RO systems require a storage tank.

The tank usually takes up space under the counter, thus a disadvantage to persons with tiny under counter spaces.

RO systems have to hook up to the drain because the waste water (water with the dissolved inorganic materials) has to be flushed away. Approximately 1 to 4 gallons of filtered water get converted to waste water for every gallon.

To produce quality, a reverse osmosis system has to operate under high pressure, a minimum of 50 psi. If your home experiences low pressure, you’ll have to install a booster pump.

  • Installation

An RO system is more complex to install, the reason why you might require professional help to complete the task.

Although some models come pre-assembled, some require setting up from scratch. You will have to make a number of connections from the feed supply line to the storage tank, air gap faucet, and the drain line for the waste water.

  • Cost

Although reverse osmosis systems have a higher upfront price ($200-$400) compared to ultrafiltration systems ($150 – $150), they are more affordable in the long run.

A reverse osmosis membrane boasts a long lifespan than a UF membrane. The system also requires fewer replacement parts.

What is Ultrafiltration?

Ultrafiltration is a water purification process that forces water through a membrane filter.

Higher molecular weight solutes and suspended solids are left on one side of the membrane while the water and low-molecular-weight solutes filter via the membrane to the permeate side.

Ultrafiltration produces quality water no matter the source. It eliminates most organic molecules, viruses, and a range of salts from the water.

  • Type of Membrane Technology

Ultrafiltration removes particulates and solids on a microscopic level. It has a hollow fiber membrane whose pore size is 0.02 microns.

Taste-wise, this water filtration method retains minerals and is thus the best for persons who like water rich in minerals.

  • Contaminants Removed by Ultrafiltration

Ultrafiltration removes only solid particulate matter. And because it does so on a microscopic level, it filters out the vast majority of contaminants like sediment and chlorine.

If you want to retain minerals like magnesium and calcium in the water, ultrafiltration might be the best option.

  • Storage

Ultrafiltration systems produce water in demand and thus don’t require a storage tank. It hooks up to a specially dedicated faucet.

Water comes out through the filter at a gallon per minute, thus quite fast.

UF doesn’t produce waste water and operates even under low pressure

  • Installation

Depending on the UF system you want for your home, it can be easy or a little hard to install. For instance, installing a system with a flushable membrane might require professional help.

Such systems require making a few connections from the feed supply line to a dedicated faucet or supply line and the drain line to flush the membrane.

If installing a UF without a flushable membrane, on the other hand, you just need to connect the unit to the feed supply line and to the outlet supply or the dedicated faucet, and you are done.

  • Cost

UF systems come at a cheaper price but are more expensive in the long run. The units have a price range of between $150 to $200, but you’ll have to replace the filters and membrane more frequently than with an RO system.


Both reverse osmosis and ultrafiltration feature outstanding water filtration properties. Although powerful and effective, they differ when it comes to the range of filtration.

While reverse osmosis eliminates almost every contaminant from the water, including minerals, ultrafiltration only gets rid of solid particulate matter.

However, it’s good to note that each system has its pros and cons. It’s therefore important to consider their benefits and disadvantages before deciding on the system to get for your home.

When you buy something through our affiliate links, we earn a commission without you having to pay extra.