How to buy Water Purifier Guide

What is the meaning of UV in water purifier

UV stand for Ultra Violet and a UV water purifier means a water filter which uses UV or Ultra-Violet light to kill germs, bacteria, protozoa, cysts, etc. in water. The term UV also appears commonly as RO UV UF in wter purifiers and the meaning of RO UV UF in water purifier is that it uses RO and UF membranes together with a UV light steriliser. Here is a what a UV water purifier looks like inside.

UV water purifier showing how the water gets disinfected while flowing arround the ultraviolet light source

The arrows show the direction of flow of the water upwards and passing arround the UV bulb. Water should always flow upwards in a UV filter to make sure that there are no air pockets and that the area around the UV bulb is filled with water. There should be a safety mechanism in UV water filters so that electricity does not come on, if there is no water around the UV purifier bulb. The purpose of UV water purifier is to kill the harmful microorganisms such as bacteria and viruses in drinking water while it flows arround the UV lamp. With a Point of Use UV sterilizer you will have the peace of mind that the water is properly disinfected prior to drinking.

How UV works in water purifier

How UV water purifier works is by killing germs in water by shining the strong UV or Ultraviolet rays on the germs in Water. The UV Ultraviolet rays penetrate the cells of bacteria, virus, cysts and destroy their ability to reproduce. Without this ability, these organisms cannot multiply and eventually die.

UV water purifiers have a simple but very effective process, with the UV water purifier light killing upto 99.99% of germs in water. The normal UV water purifer for a Point of Use drinking water purifier in the kitchen, will use about the same amount of energy as a 40 watt light bulb. It is possible to connect the UV water purifier to an inverter or UPS, so that it can be operated even when there is no electric supply. The problem with UV water purifier is that it kills the germs but its bodies remain in the water. RO water purifier purifies water by completely removing the smallest of germs, viruses and bacteris from the water.

UV water purifier bulb or lamp

The most important part of a UV water purifier is the UV bulb or lamp. It is this UV bulb which produces the ultra-violet light source. To protect the bulb from direct contact with the water there is a quartz glass sleeve around the UV tube-light which protects it against water entry and consequent electric shorting. The quartz sleeve should be of the correct quality of glass to allow the glass to be transparent to short wave UVC light of 254 nanometres, the most effective UV light wavelength to kill germs in the water.

UV water purifier with its parts and description

We have above an image of an advanced UV water purifier. All the important parts of the UV water purifier are marked. This UV water purifier is unique in that it has a special wiper mechanism which can wipe the surface of the quartz glass sleeve surrounding the UV lamp. As explained later in this page, the quartz glass sleeve protecting the UV lamp can get dirty and scaled up, and this will make the UV water purifier ineffective by blocking the UV rays. So to overcome it, this particular UV water purifier has a patented UV wiper mechanism to clean UV quartz sleeve, which can manually clean the surface of the UV quartz sleeve while the UV water purifier is working. This is a very good solution for one of the main drawbacks of UV water purifier, that is the UV lamp's ultraviolet rays can get blocked by dirt or bio-films formed on the protective quartz glass sleeve around it.

There are several manufacturers of UV tube light used as the light source in water purifiers. Some of these manufacturers may not be producing UV light but just colored light. Make sure that the UV bulb or the UV lamp inside a UV water purifier is from a well known manufacturer whose quality you can trust.

UV water purifier wavelength

UV light wave spectrum with most effective wave length to kill bacteria

The image here shows the wavelength spectrum of light. The most effective wavelengths for disinfection by light is within the UV-C band of the spectrum, with the most effective wavelength being 254nm. Short wave ultraviolet radiation, in the 200 to 280 nanometers range is known as the "C" band or UV-C (UVC). The UVC range of shortwave ultraviolet light is also called UVGI - Ultra Violet Germicidal Irradiation. UVC band of ultra violet light rays penetrates into the cells of microbes and alters their DNA molecule thus preventing multiplication and ultimate death.

Steripen portable UV water purifier

Steripen portable rechargable battery operated UV water purifier

Shown on the right is the unique Steripen portable UV water purifier model 'ULTRA'. This UV water purifier is portable and works off a rechargeable battery. On the right is shown the UV water purifier in action disinfecting a glass of water. You need to keep the UV light lit inside the glass for a minimum of 45 seconds to be sure that the water in the glass has been disinfected. So it is a very convenient water purifier to be carried along with you in your travels, to purify your drinking water just before you drink it. You will be the centre of attraction in a restaurant when you are using it, but you may not be very popular with the restaurant owner.

Steripen guarantees that in just 45 seconds, your water is safe to drink. To quote from their site "SteriPEN is proven to be safe and effective, eliminating over 99.9% of bacteria, viruses and protozoa that cause water-borne illness. SteriPEN has earned the Water Quality Association’s Gold Seal, certifying its effectiveness. Ultra, from SteriPEN, is the most advanced UV water purifier in the world. Rechargeable and easy to use – the smiley face tells you when the water is safe to drink – it’s a great gift for the Dad who loves the outdoors."

UV Water filter disadvantages

UV light inside these purifiers gets blocked when scale forms on the UV bulb, due to heat from the bulb. The scaling problem is intensified when UV unit is 'on' and there is no flow of water through it. If the UV bulb is kept 'off ' then chances of bio-growth like algae or slime, forming on the glass around UV bulb exists, and this could block the UV rays. Therefore either 'on' or 'off ', UV can become ineffective after some time.

Which is better RO or UV Water Purifier

RO and UV water purifiers work on completely different technologies. A UV water purifier uses ultraviolet radiation from a UV lamp placed inside the water to irradiate the water arround it and thus kills all germs in the water around the UV lamp. The UV lamp only kills the germs but the bodies of the dead germs remain in the water. Separate filters are required to remove the germs physically.

An RO water purifier on the other hand physically removes all germs and viruses in the water by filtering the water. So the answer to the question 'Water Purifier RO or UV better?' will be that the better water purifier is RO. An RO water purifier also remove salt molecules which are many times smaller than the smallest of germs. So the answer to the question 'RO or UV water purifier which is better?', is that RO water purifier is better than UV water purifier. For more about UV vs RO visit our page RO vs UV vs UF.

Best way to buy Water Purifiers in India

The best way to buy Water Purifiers in India is to first look at all models of Water Purifiers available online at the leading online Retailers in India. For example on the online webpage of All Water Purifiers available in India on, you will find the full range of Indian Water Purifiers complete with their best discounted price and full specifications. This is great information, and you can decide on which model of water purifier to buy. With the model of water purifier you want to buy finalised, you can go to local shops to try and find the model of water purifier you have chosen and see if you can get at similar price of that at In most cases the price from Amazon will be cheaper, because they buy in bulk from the manufacturers direct and they sell huge volumes because they are the world's largest and most trusted online retailer. If you buy from Amazon, they will arrange to have the water purifier installed in your house, usually free of charge.

Warranty and other facilities offered through Amazon are usually better than what you can get from local agents of water purifiers.

All pages in our website

Below are links to all the pages on this website and we hope you will make full use of all the great information about Indian Water Purifiers provided here.