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Ultrafiltration vs. Reverse Osmosis

By Sheila Anthony

You want a filter cooler or filtration system, but you can’t decide between a reverse osmosis or an ultrafiltration one. What’s the difference anyway? We lay it out in this quick read.


How Does Ultrafiltration Work?

Ultrafiltration (aka UF) is a barrier method of filtration and is typically the third stage in a 4-stage process. After prefiltration by a sediment and pre carbon filter, incoming water enters the ultrafiltration cartridge which consists of a membrane perforated with pores 0.1 microns in diameter. The water flows through the pores, and anything larger than 0.1 microns is blocked from moving on to the final stage of filtration and then to a dedicated faucet at the sink.

Notably, ultrafiltration removes solid particulates only, not dissolved solids.

Set up is quick and easy with ultrafiltration. No wastewater is created, so there’s no hole for a wastewater line that needs to be drilled.

The ultrafiltration filter needs to the changed every 6 to 12 months, depending on use and the home’s water quality, and the filter works very efficiently even under low water pressure conditions.

Here are some of the most common contaminants that ultrafiltration removes:

  • Bacteria
  • Copper
  • Cysts
  • Lead
  • PFAS
  • Pharmaceuticals
  • Protozoa
  • Viruses

Brio offers premium ultrafiltration coolers that are perfect for home or office.


How Does Reverse Osmosis Work?

Reverse osmosis (aka RO) is also a barrier method of filtration and is also the third stage in a 4-stage process. Reverse osmosis leverages natural osmosis by exerting pressure on the incoming water and forcing it the other way through a membrane with pores 0.0001 microns in diameter.

Contaminated water is removed through a wastewater line connected to under-sink plumbing while the purified water moves on to the final stage of filtration.

Notably, reverse osmosis not only reduces solid particulates, it also significantly reduces total dissolved solids (TDS). In both cases by 99.97%. 

Setting up a reverse osmosis system takes a little more effort than an ultrafiltration system. As mentioned, reverse osmosis produces wastewater and, therefore, includes a wastewater line that must be connected to a drainpipe via a drilled hole. This is fine if you're a homeowner, but if you rent, you'll need permission from your landlord before drilling into a pipe. 

Options for dealing with wastewater without having to drill a pipe include collecting it in a bucket and either pouring it down a drain or reusing it. It's something to think about, but depending on your situation, it may be more of a hassle than it's worth.

And whether you or your landlord pays the water bill, please note that a typical tank undersink RO system has something like a 1:4 ratio. That means for every one cup of pure water dispensed, four cups of wastewater are sent down the drain. This will impact water bills.

The Brio G20-U RO Undersink Filtration System offers a compelling 2:1 purified-to-wastewater ratio. For every two cups of purified water dispensed, only one cup of wastewater is routed down the drain.

Depending on the quality of the source water, the reverse osmosis filter needs to the changed every 12 months or so. And unlike ultrafiltration, a reverse osmosis filter needs optimal water pressure to do its job effectively.

As mentioned, the biggest difference between reverse osmosis and ultrafiltration is a reverse osmosis cooler or system's ability to remove dissolved solids from the water, which is something ultrafiltration wasn’t designed to do.

Bolded are just some of the contaminants reverse osmosis can block in addition to the particulates that ultrafiltration can block:

  • Arsenic
  • Bacteria
  • Calcium
  • Copper
  • Cysts
  • Fluoride
  • Lead
  • Magnesium
  • Nitrates
  • PFAS
  • Pharmaceuticals
  • Protozoa
  • Sulfates
  • TDS (like chloride, salts/sodium, and potassium)
  • Viruses

Which One Is Right for You?

Choosing between ultrafiltration and reverse osmosis is reminiscent of the old real estate adage: Location, location, location. Here are some things to get you thinking:

Do you rent or own?

UF doesn't require any drilled holes, so most likely no landlord approval is needed (but check your lease).

Do you live in a rural area with farm runoff that contains nitrates and nitrites?

Only RO can take out these harmful TDS.

Do you live in a rural or desert area with naturally high levels of arsenic?

Again, only RO blocks arsenic.

Do you live in a city or suburban community with a great municipal water supply but aging lead-soldered pipes through which that water travels to your home?

UF is perfect for removing bacteria and lead.

Is white scale wreaking havoc on your plumbing and requiring expensive repairs?

White scale is caused by calcium and magnesium, which are total dissolved solids. Again, RO comes to the rescue on this one.


Aside from where you live, health and plumbing needs should also be considered when deciding which filtration system is the right one for you.

But it's comforting to know both are excellent filtration systems that will result in reassuringly clean, fresh water.

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