How to buy Water Purifier Guide

What are the different types of water purifiers?

These are the main types of water filters or purifiers that are used to purify water. Which water purifier to use will depend on the impurities that are in the raw water and the quality of the purified water required. If it is required to remove dissolved salts in water, then only a water distiller or a membrane ( NF or RO) water purifier can remove salts from water. :

  1. Activated Carbon Filter
  2. Sediment Cartridge Filter
  3. Gravity based water purifiers
  4. Adsorbent Media based water purifiers
  5. UV or UltraViolet water filter
  6. Membrane water filtration
    • UF UltraFiltration Membrane water filters
    • NF or NanoFiltration Membrane water filters
    • RO membrane filter
  7. RO+UV+UF combination water purifiers

A summary of each of these different kinds of water purifiers are given below with link to dedicated separate page explaining in more detail the advantages and disadvantages of each type of water purifier.

What is Activated Carbon Water Purifier?

Activated Carbon in water purifiers removes many dangerous organic chemicals like pesticides which may be present in the water. Activated Carbon in water purifiers also removes chemicals in water which cause water to taste bad. So it is good to have an activated carbon water filter purifier for drinking water

Activated Carbon used in water purifiers are mostly made from coconut shell charcoal which has been activated using steam. When the raw coconut shell charcoal is subject to steam under pressure, gases and organic matter in the coconut shell charcoal gets replaced by hot steam, thereby creating billions of pores within the coconut charcoal. These micro pores in the activated coconut shell charcoal has the ability to absorb, technically known as adsorption, organic chemicals in water. So Activated Carbon is very effective in removing from water most toxic organic compounds like pesticides and heavy metal organic compounds. Thus the water becomes safe to drink and also tastes much better.

Humans knew the process of filtration of water through charcoal for more than 5000 years. The use of charcoal beds for filtration of water has been discovered in ancient Egyptian and Indian Civilisations by archaeologists. Activated Carbon used today is the same type of charcoal used then, but now the carbon is activated by high temperature steam treatments. ......More from our page on Activated Carbon for water purification

What is a Sediment Filter Water Purifier?

Sediment cartridge filters are usually the first in a series of different filters used in the more sophisticated water purifiers. The primary job of a sediment filter is to remove the larger solid particles like mud, dirt, sludge and other such solid particles in water. Pore size of the sediment filter is usually 20 microns. Sediment filters can get blocked but it can be cleaned and reused. ......More from our page on Sediment filter cartridge water purifiers

Adsorbent Media based water purifiers

The adsorbent based water purifiers, other than Activated Carbon, are very rarely used. One famous Adsorbent based water purifier is the Whirlpool Defender. Whirlpool Defender which is very effective for tap water purification. Another Adsorbent based water purifier is the Aquaguard Aquasure Amrut water purifier based on an adsorbent material called Kintau Magnet.

The Adsorbents used in these types of water purifiers are complex naturally found Alumina Minerals. Some metal oxides can also function as water purification media. Water softener resins can also be technically considered as an adsorbent water purification media. But all these are not widely used in water purifiers.

What is a Gravity based water purifier?

Gravity based water purifiers are a combination water purifier using multiple filtration processes. Gravity water purifiers are cheap and used by many in India. The main advantages of gravity water purifiers are that they are cheap and work without electricity.

Gravity water purifiers, as the name implies, depends on gravitational forces to make the water flow through the several filter cartridge elements. Gravity water purifiers normally works without electricity, but in cases where there is a built in UV (not available in India) electricity would be required. The flow through rate of gravity filters through its filters are very slow, almost drop by drop into the storage tank below. Since Gravity filters have large storage tanks, there will always be enough filtered water when required.

Gravity water purifiers usually have multistage filtration process. This may include one or several of the following types of water purification filtration process: Sediment filter cartridge, Activated Carbon filter, Adsorption media filter, Germ killing media filter element, UF filter element.

What is a UV Water Purifier?

UV or Ultra Violet light rays are capable of killing Bacteria, viruses and other disease causing organisms. Thus when UV light passes through water it sterilises the water killing all the germs present in that water. How efficient a UV Water Purifier is, depends on several factors and these are discussed in more detail in our dedicated page on Ultraviolet UV water filter purifiers

What is Membrane Water purifier?

Membranes are very thin sheets of a synthetic plastic material which have very fine holes or pores. The pore size determines what type of a membrane it is. There are 3 types of Membranes known as UF UltraFiltration Membrane, NF or NanoFiltration Membrane and RO membrane. Each of these Membrane types are briefly described below. ...... More from our dedicated page about Membrane Water Purifiers

What means UF in water Filtration?

Membranes with larger pores between .01 and .1 microns are classified as UF or UltraFiltration Membranes. UF cannot filter out of water particles smaller than their pore size. So it cannot filter out particles smaller than 0.02 microns. At .02 Microns UF can filter out Bacteria, Viruses and all disease causing bio organisms, but it is not capable of removing dissolved salts from water. The advantage of UF water purifier is that it can work without electricity on the low pressure available in most domestic water taps. More from our page on Ultrafiltration UF membrane water purifiers

What is NF Water Purifier?

NF or NanoFiltration Membranes have smaller pores than UF membranes and has the capability to remove larger dissolve molecules of chemicals – like di-valent molecules of Calcium, Magnesium and other hardness causing salts. Thus one of the important applications of NF Membranes is to soften water or to remove water hardness and making hard water soft. Since the pores of NF membranes are bigger than the pores in an RO Membrane, less pressure is required by NF membranes. So NF membranes are very efficient in softening hard water. More from our dedicated page about Nanofiltration NF membrane water purifiers

What is RO Membrane in Water Purifier?

RO has the smallest pores among water purification membranes and can remove all dissolved salts in water. Thus water after passing through an RO water purifier membrane comes out without any dissolved salts, almost as pure as distilled water. The disadvantage of RO membrane is that it requires high pressure to force water through the minute pores of an RO membrane. More from our dedicated page about Reverse Osmosis RO water purifier

What does RO+UV+UF means in water purifiers?

The term RO+UV+UF in water purifiers means that it is a water purifier having three types of water purification process included in the one water purifier. Since full form of RO is Reverse Osmosis, full form of UV is UltraViolet and the full form of UF is Ultrafiltration, a water purifier with RO+UV+UF will have Reverse Osmosis + Ultra Violet + UltraFiltration processes built in.

How water purifiers work?

Water purifiers can be just a simple water filter with a cartridge filter element to the more advanced water purifiers using membranes for water filtration followed by sterilisation with UV filter.

We explain how different types of water purifiers work and once you understand how water purifiers work it is easy to decide on which type of water purifier to buy.

Which is Cheap and best water purifier in India?

For most houses in India supplied with Municipal or Corporation water, just a simple cheap water purifier with a sediment filter cartridge is enough, and is the cheapest solution. The sediment cartridge water purifier is just a very fine sieve through which when the water passes, solid particles bigger than the size of the sieve holes or pores gets trapped and filtered out of the water.

Modern day water filters using the sieving method must have evolved from the Middle Ages, when pieces of cloth were used by people to filter their drinking water from river, pond, well or rainwater. During this filtration process through cloth, when the cloth got dirty and clogged, they would have rinsed the cloth clean and reused it. The same way most of these cheap water filter cartridges can be washed and reused.

What is Pore size of water filter

Pore size of water filter Vs micron size of water contaminants
Pore size of water filter Vs micron size of water contaminants

Water filtration still depends on passing the water through fine pores or holes, only now the pore sizes have become very much smaller. The size of the pores or holes in a cloth is very large when compared to modern day filter media. While the pore size of the cloth would be measured in fractions of a mm or millimeter (1/1,000 or 0.001 Meter) a modern day water filter pore size is measured in Microns or a micrometer normally written as μm = 1 by a million or 0.000001 Meter. That is about a thousand times smaller than the pore size of plain cloth.

The smaller size of the pores means that it is more difficult for the water to pass through them, hence the water needs more pressure to pass through the smaller pores. In the case of gravity water filters the pressure is low, which means the flow of water will be less, and so in gravity water filters the water is filtered almost drop by drop and it will take a long time to filter water. When the pores of the water filter are small, more dirt gets filtered out, and hence smaller pore size filters gets clogged and blocked more easily.

Membranes used by Nature to purify water

Nature uses membranes to purify water. The coconut tree purifies dirty ground water using membranes in its roots, and sends up the purified water with the addition of nutrients, to its tender cocoanuts to give us that refreshing tender coconut water. Membrane water purification technology that we use today uses membranes similar in properties to the membranes in the roots of a coconut tree. We use synthetic membranes made out of very thin sheets of a plastic material which have very fine holes or pores. The pore sizes are different in different types of water purification membranes. Membranes are classified according to the pore size of membranes as Micro-filtration membranes MF, Ultra-filtration membranes UF, Nano-filtration membranes NF and Reverse Osmosis RO membranes. The pore size of RO membranes are the smallest and can filter out dissolved chemicals out of water and thus even convert salt water into fresh water. ...... More from our dedicated page about Membrane Water Purifiers

Which type of water purifier is best in India?

Selecting a water purifier in India for house depends on the quality of water you get in the house. As explained above there are different water purification technologies and selecting which type of water purifier is best depends on the type of water or impurities in water that is there in the house. Below we will explain how a good multi-stage water purifier works combining different water treatment technologies in a single water purifier. This should help in understanding different water purification technologies and in deciding which kind of water purifier is best in India.

Multi stage home water purifiers and how they work

Modern home multi stage water filter purifiers combine different kinds of water purifiers into one unit. The different stages of a multi stage type of water purifier are as follows:

  1. The first stage of water purification in all home water purifiers is to get rid of the larger solid particles like mud and dirt with a sediment filter. Pore size of the sediment filter is usually 20 microns. If the water contains a lot of mud or other larger particles, then this cartridge element becomes blocked quickly. It can be removed, cleaned by jetting with water and reused. It is like a cloth being reused after rinsing.
  2. The second stage in a home multi stage water purifier is a finer filter with pore size varying from 5 microns down to 1 micron or even less. These fine pore water filters removes larger germs like parasites. The smaller the pore size, the more efficient it will be in removing microbes and germs from water. The disadvantage of having very small size pore water filter is that a higher water pressure will be required to drive the water through. If the pressure is not sufficient, the water coming out of the filter will be very slow. Since multi stage home water purifiers usually have a germ killing device like UV (Ultra Violet) at the last stage of the multi stage water purifier, any germs passing through the finer filter will be killed later. So a compromise is made by having a 5 micron second stage filter cartridge.
  3. The third stage in a multi stage home water purifier is an Activated Carbon water filter in the form of an activated carbon block cartridge element. The active carbon water purifier adsorbs toxic organic chemicals like pesticides. It is very important to understand that there are many qualities of activated carbons and some may not be very efficient. Also the activated carbon has limited capacity to hold harmful chemicals, so make sure it is changed at the recommended intervals. ...More about Activated Carbon from our page on Activated Carbon
  4. The fourth stage will normally be a germ killing device, usually a UV water purifier which has a UV light to kill any remaining germs in the water. Some water purifier manufacturers call UV water purification as 'e-boiling' - See our page on Ultraviolet UV water filters. Other methods in the final stage to kill germs could be by passing water through special media which release chlorine, or through media with nano-silver particles.

The filtration stages 1 to 3 described above can be as separate filtration units one after the other or it is possible to combine all stages into one filter cartridge by having the different media one under the other, so that the water flows through each media.

As the filter removes the particles from the water, their pores are getting blocked and water pressure is being lost. This means over time the flow out of the filter becomes slower and slower until it almost stops. The time it takes for the filter to become blocked depends on how much dirt there is in the water. Most water purifiers have replaceable filter elements called cartridges, and it is a simple procedure to change cartridges. Once cartridges are replaced, the flow will be restored.

Home water purifiers with RO

Home water purifiers with RO are now the most popular water purifier in India. RO or reverse Osmosis water purifiers use RO membranes to purify water. There are other types of membranes for water purification but RO water purifier is the most popular in India. Other types of membranes in water purifiers are Ultrafiltration UF membrane water purifiers which can remove all bacteria, virus from the water but not any dissolved chemical impurities in water. Then there is Nanofiltration NF membrane water purifiers that removes everything that the UF water purifier removes (bacteria and Viruses) plus it also removes larger molecule salts in water, like Calcium and Magnesium and some of the Heavy Metal salts.

Salts like sodium Chloride remain in the water in a NF water purifier. NF water purifier is capable of softening water. Finally there is the Reverse Osmosis RO water purifier which removes all impurities in water – virus, bacteria and all salts. So RO water purifier is the best type of water purifier available in India for drinking water.

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.

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