UV Vs. Reverse Osmosis

UV Vs. Reverse Osmosis

Let’s face it, tap water, in many parts of the US, is no longer of the same quality as it once was. As such, in recent years, water purification systems have become extremely popular in most urban and suburban households. Homeowners searching for the best water purifiers are often recommended a Reverse Osmosis (RO) or UV system to fulfill their filtration needs. Although they are both known for their effective purification of water, they aren’t the same.

The main difference between UV and RO is how effective they are at eliminating contaminants from unfiltered tap water. RO filters are a lot more thorough and provide the purest form of water. UV systems can’t get rid of everything present in water but are more affordable and easier to run than RO systems. They also offer more natural-tasting water.

To make the right choice on what system would work best for your household, let’s take a deeper look at the similarities and differences of each filtration process.

Read my comprehensive article about reverse osmosis.

Reverse Osmosis Vs. Ultraviolet (UV) – A Detailed Comparison

We have drawn up this comparison to create awareness regarding these two water treatment systems.

The main highlight of our comparison is the level of contaminant removal and bacterial disinfection that each system provides. Knowing these facts about the system will help you make more informed choices.

Water treatment process

The RO system moves water molecules, from high concentration to low concentration, through an ultrafine semi-permeable membrane. This membrane has a pore size of 0.0001 to 0.0005 microns which helps it filter out 90 – 99% of all contaminants found in water.

Apart from the membrane, other specialized filters are also added to remove sediment, total dissolved solids (TDS), metals, chemicals, and toxins from unfiltered tap water.

A UV system uses ultraviolet rays to kill harmful bacteria and microorganisms in the water. This results in total disinfection of all pathogens.

Once the water has been UV treated, it is free of harmful microbes. However, it must be noted that UV rays do not physically filter or remove anything from the water.

Maintenance requirements

The maintenance of a reverse osmosis system requires:

  • Changing the filters every 3, 6, or 12 months, depending on the usage.
  • A complete disinfection of the system, at the time of filter change.
  • Replacing the semi-permeable membrane every 2 to 3 years.
  • Servicing many electrical parts every few months for the system to run smoothly.

The maintenance of a UV system requires:

  • Changing the UV lamp once a year.
  • Conducting quartz sleeve cleaning.
  • Proper plumping disinfection.

Contaminant removal

An RO purification system removes all impurities, heavy metals, chemicals, and total dissolved solids from the water. This includes chlorine, lead, sodium, dissolved solids, herbicides, pesticides, copper, chromium, sulfate, calcium, potassium, magnesium, phosphorus, nitrate, radium, arsenic, dead microorganisms, and much more.

In contrast, a UV system doesn’t remove any contaminants. Rather, it kills all the viruses, protozoa, and bacteria. A strong UV light will even kill thick-celled microorganisms such as Cryptosporidium and Giardia. Although dead, these microorganisms still float in the water.

Below is a table that shows the most common contaminants found in domestic water and what each filter can and cannot filter.

Unfiltered Tap Water UV RO
Bacteria Disinfection Yes No
Chlorine Removal No Yes
Lead Removal No Yes
Pesticide Removal No Yes
Arsenic Removal No Yes
TDS Reduction No Yes
Sodium Removal No Yes


Other articles about reverse osmosis treatment efficiency:
Does Reverse Osmosis Remove Chlorine from Drinking Water?
Reverse Osmosis Filtration: Removing Lead From Drinking Water
Does Reverse Osmosis Remove Glyphosate from Drinking Water?

Energy consumption

Both systems utilize energy differently. RO systems, however, require a lot more energy as the process requires high water pressure to push water through the membrane. This requires a water pump that will consume energy resulting in a slight increase in your utility bill.

UV systems don’t require a boost in water pressure to function. Rather, electricity is used to power the UV lights. The energy consumption is so minuscule that it is unlikely to make any difference to your total utility bill.

The time required to purify water

An RO system takes much longer to purify water, as unfiltered water has to pass through several stages of purification.

A UV system, on the other hand, can purify water almost instantly.


The RO system comes with 5 to 15 liters of storage space. A day’s worth of filtered water can be stored there for later use.

On the contrary, the UV system does not come with any storage.


An RO system can last forever as long as you maintain and replace parts as needed. All the parts of a reverse osmosis system are readily available and must be replaced at the right time.

A UV system can also last forever as long as you replace the UV lamps after 8000 to 9000 hours of usage or roughly a year. Although UV lamps do not burn out, they lose their intensity over time and become less effective.

Best Used For

An RO system is the better choice when dealing with water sourced from a well or water that has higher levels of metals, chemicals, and TDS.

The UV water purifier is best suited for water supplied by the municipality that is deemed safe for drinking purposes.


One of the biggest downsides of the RO system is that it results in a lot of wastewaters.

On the contrary, UV purifiers waste no amount of water.


The average price for an RO unit for the whole house can range anywhere from $750 – $7500. These units are expensive as they have to be integrated with the mainline of your home.

The average price of a UV water filtration system starts at $70 and can go up to around $600 for the more expensive and durable models.

Frequently Asked Questions

Can I combine reverse osmosis and a UV purifier system?

Yes. To purify water sourced from a well, it is best to combine the two systems. The UV light will kill all the pathogens and the RO system will remove all the physical impurities, making the water completely safe to consume.

Do UV purifiers change the taste of the water?

No, UV purifiers do not affect the taste or odor of the water.

Is there anything that is not removed by an RO system?

RO systems are unable to remove most organic compounds, bacterial microorganisms, by-products of chlorine, and dissolved gases.

Final Thoughts

On the whole, both filtration systems make for excellent water purifiers. To choose between them, we must pay attention to the source of the drinking water. If the unfiltered water has heavy metals, chemicals, or TDS, it is best to opt for RO filters. However, if your domestic water supply is fairly safe, a UV filter can also prove to be an effective and affordable choice.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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