The Ultimate Guide for Buying a Water Purifier for Home (2022)


We’re pretty sure you’re convinced that every penny you spend on a great water purifier is a penny spent wisely, because of the health benefits of drinking purified and uncontaminated water.

Even apart from that, there are literally dozens of reasons for you to look for the best water purifier and get one home; for instance, water purifiers ensure:

  • Safety from life-threatening waterborne diseases that may be caused by contaminated water
  • That the weird taste of chlorine, calcium carbonate is removed from tap water (which means it won’t spoil your coffee!)
  • Little to zero scratchings, spotting and scaling on the surface of your kitchen utensils.

Video Tutorial – Things to Look for When Buying a New Water Purifier (Hindi Audio)

Water Purifier Buying Guide 2022

This Water Purifier Buying Guide will help you identify the right water purifier for your home or office; read on.

Before we discuss the different types of water purification technologies and which one out of these suits your needs, it is important to first understand the different types of impurities found commonly in drinking water. Because then only we’ll be able to understand the need for such varied types of water purifiers.

Different Types of Impurities Found Commonly in Drinking Water

The type of impurities found in the drinking water coming to your home mainly depends on the source and distribution medium of water. The most common sources of drinking water are: lakes, rivers, bore wells, harvested rainwater, piped municipal corporation supply, water tankers, etc.

The quality of water, level of impurities like harmful pollutants, chemicals and biological impurities like bacteria and viruses, and hardness, all depend on the source of water.

Most common types of impurities in water:

Un-dissolved solids such as sand and mud River, borewell, or piped water where pipes are damaged Muddy or turbid appearance
Dissolved inorganic salts like Sodium & Potassium Borewells and seawater Salty or brackish taste
Dissolved inorganic compounds like Calcium & Magnesium Borewells and river water Hardness and scale formation
Organic compounds Lakes and ponds Foul smell or bad odor
Disinfectants like Chlorine Municipal piped water supply Bitter taste
Biological impurities like bacteria & viruses Piped water where pipes are damaged, water tankers Biological contamination, waterborne diseases

Usually, water from lakes, rivers, and harvested rainwater will have a low TDS (Total Dissolved Solids) as compared to water from bore wells. Borewell or groundwater generally has high TDS and may also contain harmful chemical impurities like lead, arsenic, etc. Piped water supply or water stored in tanks is generally more prone to biological contamination (if the pipes are damaged or the storage tanks are not cleaned frequently).

Identify the Water Type – Soft or Hard Water

Water can be classified as soft or hard based on the level of dissolved solids in water. Total Dissolved Solids (TDS) is regarded as the degree of hardness and is measured in units of Parts Per Million (PPM) or Milligrams per Litre (mg/L).

1 ppm = 1 mg/L

Water with TDS values ranging between 150-300 ppm is considered to be soft water, while water with a TDS value higher than 500 ppm is considered to be hard or contaminated water.

Hard and Soft Water

What’s the source of the water you get supplied to your home? If it comes from underground water, supplied by water tankers, or drawn from deep dug bore wells, then most probably it’s hard water. Now, hard water contains pretty high percentages of dissolved solids like calcium, magnesium, heavy metals, fluorides, and arsenic. All these dissolved impurities make hard water unfit for human drinking. On the other hand, water sourced from rivers, rainwater harvesting systems, lakes, and municipality-managed storage and delivery system is generally termed as soft water. Soft water, though not as dangerous, also needs purification before it can be deemed safe for human consumption over the long run.

You may also like: How to Make Hard Water Soft

Water Purifier Types, and Mapping them to Your Water Type

1. Reverse Osmosis (RO) Purifiers
To understand the working of RO, we need to first understand what Osmosis is.

Osmosis Process

In the normal osmosis process, the water naturally flows from an area of low solute concentration (low TDS level), through a membrane, to an area of high solute concentration (high TDS level). The pores of the membrane are very small (about 0.0001 microns), water molecules being smaller are allowed to pass through and the smallest dissolved impurities and bacteria are trapped.

As the name suggests, Reverse Osmosis (RO) does the opposite of Osmosis, that is, push the water molecules from the region of higher TDS level to the region of lower TDS level. This is achieved by applying external pressure with the help of a water pump to reverse the natural flow of water. Water with impurities or high TDS is pumped at high pressure into the RO chamber, this pushes the water molecules across the semi-permeable membrane to the other side while leaving the dissolved solids and other impurities behind. All the dissolved solids and impurities along with some input water, also known as RO wastewater, are discharged through a separate outlet.

Reverse Osmosis Process

RO purifiers are therefore always recommended for purifying water that has a high TDS level. The TDS level of the output drinking water from the RO purifier is very low as compared to the input water.

Some Drawbacks of RO Technology

  • Requires Electricity: A high-pressure electrical water pump is used to apply external pressure on the input water, hence RO purifiers cannot work without electricity.
  • Wastes Water: A significant part of the input water is discharged along with the dissolved impurities, which results in unnecessary wastage of water. On average, RO purifiers produce 3 litres of wastewater for every 1 litre of purified water.

2. Ultrafiltration (UF)
Like RO, Ultrafiltration also uses a semi-permeable membrane to purify water. After reading the first sentence, you must now be thinking if both RO and UF use the same method to purify the water then what is the difference between RO and UF. Ultrafiltration or UF uses a membrane with much larger pores (appx. 0.01 microns) as compared to RO which uses a membrane with very small pores (appx. 0.0001 microns).


The advantage of using Ultrafiltration is UF purifiers can work without electricity because the membrane has much larger pores and water can pass through it naturally using the force of gravity. This means no external pressure or water pump is required. Also, since UF purifiers do not hold back any water, there is no wastage of water.

But there are some limitations of using UF purifiers, because of larger pore size, UF can only remove undissolved solids and larger impurities. It cannot remove the dissolved solids or reduce the TDS level. So, UF purifiers are not suitable for the purification of high TDS water or hard water.

RO UF Comparison

3. Ultraviolet (UV) Purification
As the name suggests, Ultraviolet or UV purification uses ultraviolet rays for the purification of water. A UV purifier works by throwing high-intensity UV rays on the water which kills or inactivates the disease-causing bacteria and viruses.

However, UV purifiers cannot remove any dissolved or un-dissolved impurities or chemicals from water. Because of this most of the UV purifiers that are available in the market use some form of external sediment pre-filters to remove undissolved impurities and an activated carbon filter to remove Chlorine and some dissolved impurities.

Therefore, UV water purifiers are only recommended for areas where the water source has a low level of TDS.

If the water has a low TDS level but is contaminated with bacteria and viruses and appears muddy then you can use a UF+UV water purifier.

4. Tap/Faucet Mounted Filters or Gravity Based Purifiers
These types of filters or purifiers are the simplest to use and provide the most basic water purification. These filters generally comprise sediment or sediment + activated carbon filters which can remove large and un-dissolved impurities like mud and sand along with some chemicals and microorganisms. Tap/Faucet Filters are very small in size and can be directly fitted on taps.

Tap/Faucet Filter and Gravity Based Purifier

Gravity-based storage purifiers are the advanced version of tap/faucet filters. These purifiers offer slightly advanced purification and come with an in-built storage tank to store input/impure water. Most of the Gravity-based water purifiers available in the Indian market now have 2 separate storage tanks for input/impure and output/purified water.

Tap/Faucet Mounted Filters and Gravity Based Purifiers are only suitable for areas where the TDS level is low and water is not highly contaminated with biological impurities like bacteria, viruses, and other disease-causing germs.

Which Water Purifier Should I Choose?

RO technology has become synonymous with water purifiers and you must have heard a lot of people referring to water purifiers as RO (like the brand Xerox has become synonymous with photocopying).

Because of this, when we talk about buying a water purifier most people think RO water purifiers should be purchased by default without considering the most important facts like the source of water and TDS level of input water.

If you have read all the above discussion then you are well aware of the fact that RO purification is required only when the water coming to your home or office has a high TDS value (generally higher than 500 ppm).

These days there are different kinds of water purifiers available in the market ranging from simple tap/faucet filters and Gravity-based purifiers to UF, UV, RO, and their combinations. This vast range of different technologies and thousands of different water purifier models from tens and hundreds of brands have increased the complexity of buying the right purifier for your home or office.

As discussed earlier, you should buy an RO purifier only if the water to be purified has a high TDS level. The Bureau of Indian Standards (BIS) has specified the maximum TDS limit for safe drinking water as 500 ppm.

There is absolutely no need to use an RO purifier if the TDS level is below 500 ppm. Because if your water source has low TDS then the RO purifier will further reduce it to a very low TDS level. This means the purified water will then be devoid of essential minerals like calcium and magnesium which are required for our good health.

If the TDS level of incoming water is below 500 ppm then you should check the incoming water for turbidity (clarity), muddy appearance, or presence of biological impurities like bacteria and viruses.

Though water purifier makers try to differentiate their products from competitors by flaunting advanced water purification technologies, most of them actually use a mix of three major purification approaches – Reverse Osmosis (RO), Ultraviolet (UV), and UF (Ultrafiltration).

If you do not want to go into the technicalities of the different purification approaches, then you can simply refer to the below checklist that helps you buy the right purifier for your home or office. Here we will list all the parameters to evaluate and choose the right water purifier according to your needs.

Below 500 ppm No No Gravity-Based Purifiers
Below 500 ppm No Yes UV
Below 500 ppm Yes No UF
Below 500 ppm Yes Yes UF or UF+UV
Over 500 ppm No No RO
Over 500 ppm No Yes RO+UV
Over 500 ppm Yes No RO+UV or RO+UV+UF
Over 500 ppm Yes Yes RO+UV+UF
  • Soft water has low TDS level; UF water purifiers work pretty well for it.
  • For soft water with a high level of biological contamination, go for a UV or UF+UV water purifier.
  • Hard water contains a higher level of TDS, apart from specific toxins; so, RO based purifiers are well suited for purifying it.
  • For hard water with a high level of biological contamination, go for a RO+UV or RO+UV+UF water purifier.
  • UF filters are best used in combination with another water purification system, as they don’t kill any microorganisms in contaminated water. UF filters only remove suspended solids from water.
  • Activated carbon based water purifiers are ideally suited to remove excess chlorine from water.

Main Components of RO Water Purifier

  • Sediment Pre-filter: In the first stage of purification, the input water is filtered using a pre-sediment filter. Pre-sediment filter not only removes fine and coarse particulate impurities/dirt but also improves the life of the RO/UF membrane resulting in a lower cost of maintenance. If the purifier does not include this as a standard feature then it can be added separately as well.
  • Activated Carbon Pre-filter: Activated carbon pre-filter removes chlorine and organic impurities like harmful pesticides from the water. Activated carbon pre-filter also adsorbs bad odor and taste-causing organic compounds from water.
  • RO/UF membranes: Water is fed into the RO membrane at high pressure using an in-built water pump. RO membrane removes the hardness, dissolved salts, pesticides and heavy metals like lead, arsenic, and mercury. It also removes microbial contaminants like virus, bacteria, protozoa, and cysts. The UF membrane also works like RO membrane but it does not remove the dissolved solids. Some purifiers use both RO and a UF membrane, the output water from both the membranes is mixed to control the TDS level of purified water.
  • TDS controller: TDS controller is used for controlling the TDS level of the output water. RO process not only removes bad impurities but also removes essential minerals like Calcium & Magnesium. TDS controller retains adequate quantities of essential minerals in the purified water by adjusting the ratio of water from RO membrane (low TDS) and UF membrane (normal TDS) in the final mix.
  • UV Filter: UV filter uses a high-intensity UV bulb to kill or inactivate any virus, bacteria, and parasites to deliver safe water.
  • Carbon Post-filter: Carbon Post-filter acts as a polisher and enhances the taste of purified water. It also removes any foul smell from water.
  • Storage Tank: This stores the purified water for later use. Make sure the storage tank is made of food grade, non-toxic material. Some of the high-end water purifiers now come with a stainless steel water storage tank. You should also check the capacity of the storage tank.
  • Display: Most of the RO water purifiers come with basic display for purifier on/off, tank full, etc. Some advanced purifiers also come with fault alert, membrane change, UV fail, TDS level indicator, purity indicator, etc.

Gravity-Based Water Purifiers – Where Do They Fit In?

Good question. Considering they’re inexpensive and effective, it’s natural that these filters excite a lot of interest, especially among first-time buyers of water purifiers. Now, these filters don’t deliver advanced water purification capabilities such as RO and UV-based filters. So, the only scenarios where they become practical options are:

  • When you don’t have optimum conditions for the installation of an electric water purifier, such as optimum water pressure, electricity, and running water supply.
  • When you need to switch homes frequently and don’t want to have bulky equipment to move around and re-install every time.
  • When you have a very limited budget.

In such situations, you could either choose to buy purified water in bulk from a convenience store or install a gravity-based water purifier.

Installation Feasibility of Water Purifiers

Most RO and UV-based water purifiers are bulky and pretty heavy. Before you buy one, make sure you know of its dimensions, and have a plan to have it wall mounted in the kitchen area. You will need to provide an inlet for electricity and another for water. Also, there must be a continuous water supply at decent pressure, particularly when the water purifier is mounted high on a kitchen wall.

Reducing and Reusing RO Waste Water

Avoid using an RO water purifier if the TDS level of the input water is below 500 mg/L and the water does not contain any harmful heavy metals like lead, arsenic, and mercury. In such a case, using a UV+UF water purifier would be more appropriate. Save water by not using RO water purifiers if RO purification is not necessary.

An average RO purifier wastes approximately 3 litres of water for every 1 litre of purified water. That means only 25% of water is purified and 75% of water comes out as waste.


It’s true. This high percentage of water wastage is a major cause of worry. If you are also using an RO water purifier at your home or office then we request you to follow the below-given tips to reduce the wastage of water and re-use the wastewater generated by RO purifiers.

  • If the output water from your purifier has very low TDS (less than 150) then it means your purifier is generating more waste water. A very low level of TDS not only results in higher wastage of water but it is also bad for our health as it is devoid of essential minerals. Increasing the TDS will not only make the drinking water healthier but also reduce the wastage. You can increase the TDS level of your water purifier using the TDS controller knob.
  • Store and re-use the RO waste water.

Final Thoughts

The sole and biggest criteria to decide the type of water purifier you should buy is the source of water and the kind of impurities present in the water supplied to your home or office. Use the suggestions shared in this water purifier buying guide to buy a new water purifier for your home or office.

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