The water supplied to most homes is usually not fit for drinking without some kind of filtration process. It could be muddy, unpleasant in smell and taste, or carrying contaminants.
There are multiple ways of purifying water that differ in their mechanisms. 
Some of these are reverse osmosis (RO), nanofiltration (NF), microfiltration (MF), ultrafiltration (UF), and UV water purification. 
These systems can be used in isolation or combination depending on the quality of the feed water. In this article, we explain how a UV water purifier works and when to use it.
What a UV Water Purifier is and How it Works
A UV water purifier used ultraviolet radiations to make water fit for drinking. It can eliminate the danger caused by impurities like harmful pathogens such as bacteria, viruses, or cysts. 
These systems are quite effective as they can deactivate 99.99% of the living organisms in the water.
They are designed to run constantly for optimal disinfection. Unlike most water purifiers, a UF filter does not waste water or create debris that requires cleaning.
Excellent for the prevention of water-borne diseases, UV water purifiers produce fresh and clean water without using any chemicals.
The absence of such cleaning agents helps provide potable water without any change in taste or odor.
The method of water purification in a UV filter is very different from that of MF, UF, or RO filters.
There is no semipermeable membrane that sieves out contaminants. Instead, a UV lamp encased in a glass quartz sleeve emits (UV-C) radiations.
These radiations deactivate the living organisms by disrupting their DNA. Because of this, when consumed, the pathogens cannot replicate. Thus, the microorganisms are prevented from causing disease.
In essence, the UV water purifier stops these pathogens from being harmful, making water fit for consumption. The lamp is encased in the quartz sleeve to protect it from water. The glass surface of the sleeve allows the lamp to emit the radiations.
Here is a quick video on how UV water system works –
The apparatus is sealed with one or more O-rings. The UV lamp is powered by mercury vapor. That is why users might see small beads rolling around the lamp. These beads are mercury in liquid form before they get vaporized to create fuel.
If you’re worried about energy use, UV filters use the same amount it would take to run a 60W bulb. These systems are sized according to the gallons produced per minute (GPM).
They are available in sizes ranging from 5GPM (for 1 point of use) to 22.5GPM (for 6 points of use). Choosing the right size for your home brings maximum satisfaction when used.
Benefits of a UV Water Purifier
UV water purifiers eliminate the need for chemicals cleaning agents in water. They get rid of pathogenic life forms by simply using ultraviolet radiation.
Chemicals like chlorine tend to leave a distinct taste or odor in water. This is not a problem with UV-filtered water. Another advantage is that UV light can deactivate protozoa as well, which is unaffected by chlorine.
Unlike RO water purifiers, a UV system does not produce any wastewater. The entire feed water gets disinfected and can be used for drinking or cooking.
This is a big plus point for areas with water shortage or people concerned about the environment. When it comes to maintenance, UV water purifiers require a minimal amount of care and upkeep.
Limitations of a UV Water Purifier
The biggest drawback of using a UV water purifier is that there are specific conditions required for its effectiveness. Without these conditions, the UV filter will not work.
The supply water must have less than 7 grains per gallon of hardness, and less than 1 NTU of turbidity. It should also have less than 0.1 PPM of tannins and UVT levels should not exceed 75%.
An iron level of <0.3 PPM and manganese level of <0.05 PPM are also required for the UV water purifier to work.
Moreover, a UV filter alone cannot get rid of turbidity, heavy metals, suspended particles, colloids, proteins, minerals, and salts.
Even though it deactivates pathogens, the carcasses of these organisms remain in the water.
Hence, a UV filter works best when supplemented with filters before and after it to eliminate these limitations.
When to use a UV Water Purifier
A UV water purifier is most appropriate when the water supply is rich in microbial life that causes water-borne diseases.
Before implementing a UV system at home, get your water tested in a certified lab. If the water contains bacteria, protozoa, cysts, and viruses, a UV filter is a good choice.
For the system to work effectively, the feed water should have the above-mentioned conditions. These include levels of hardness, turbidity, tannins, UVT, iron, and manganese.
Generally, the conditions can be created by supplementing the UV water purifier with another system. This could be RO, UF, MF, or a combination of these placed before the UV filter.
Having multiple systems working together with the UV water purifier is the best way to ensure good quality disinfection.
A UV water purifier uses ultraviolet radiations to disinfect drinking water. It does this through a UV lamp encased in a glass quartz sleeve. The sleeve protects the lamp from exposure to water and its transparency allows the radiation to emit.
These radiations can deactivate up to 99.99% of the living organisms in the water. The UV rays disrupt the DNA of the pathogens so that they cannot replicate when consumed. This prevents them from causing diseases in the body.
Other than bacteria, cysts, and viruses, the UV system affects protozoa as well. Chemicals and water cleaning agents like chlorine are not capable of this.
A UV water purifier works best under specific conditions of water constituents. This is generally achieved by supplementing the UV system with other purifiers like RO, UF, or MF systems.