- Water source (Most important)
- Storage capacity
- RO + UV or only RO
- Purchasing online or in-store and cost of the unit
- Installation: Free or charged
- Annual maintenance charge
- After sales service
- TDS controller
Water source should be your primary criteria before shortlisting a water purifier. In fact, it will help you to decide if you even need a water purifier in the first place.
Types of water purifiers:
Reverse Osmosis (RO) – Reverse osmosis is the process in which a membrane separates dissolved particles or contaminants and water, making the water fit for consumption.
Ultraviolet rays (UV) – In the context of water purifier, UV helps to kill harmful germs such as bacteria and virus.
Ultrafiltration (UF) – UF membrane further removes larger suspended particles, bacteria, virus, etc.
Most water purifiers provide a combination of RO+UV+UF, some provide only RO+UV or only RO or only UF. If water TDS level is below 500, generally huge investment in water purifiers are not recommended.
Let us understand the various terms you will come across. Some are essential while others are good to have but not very critical. This comprehensive guide will help you to assess your needs.
Sediment pre-filter: This is generally found outside the main RO unit in a separate encasement. It contains a microfilter or simply a micro spun (usually 5 microns) which acts as the first gateway and removes sediments or dust particles. This means that the pre-filter needs to be changed frequently. The time period could range from 3 months to 6 months depending on the quality of water. It also increases the lifespan of the main membrane.
Activated carbon filter: This further purifies the water by removing chlorine, and also removes odour from water by trapping organic compounds and other volatile substances.
RO/UF membrane: The water so far has been pre-treated and now enters the most important part of the RO filter, the RO membrane. This is where the main action takes place. The membrane separates dissolved particles, ions, and some minerals allowing only pure water to pass through. It is debatable whether RO removes metals such as lead, arsenic, etc. But more importantly, RO removes essential minerals. Hence, ROs are also fitted with extra cartridges which add back minerals thus making it potable.
UV Filter: This is not really a filter but a UV lamp that kills harmful bacteria and virus in the water. It does not remove dissolved solids. For this reason it is always found after RO membrane as water needs to be relatively pure before being treated by UV.
TDS Controller: This is a mechanical device that allows mixing of minerals as the RO water is stripped of essential minerals. These days there are additional cartridges to add back minerals. Many RO devices are pre-fitted with TDS controller but some may not have. Check if this is available in the water purifier you choose.
Post carbon-filter: This further enhances the taste of the water and removes any odour if present.
Storage tank: This is where the final treated water is stored. There are water purifiers without storage tank also but generally not recommended. In case there is a power failure, it may not be effective. Various devices have different tank sizes. The most common being 7,8 or 9L but it is not uncommon to find heavier tanks.
Other cartridges: As you read above in the TDS controller part, there is slight mixing of tap water with RO water to restore minerals. However, nowadays it is common to find an extra cartridge (usually between RO and UV cartridges) to add back essential minerals. The term Mineralizer will be added in the description of the product.