Compare Water Purifiers
Pre-RO Carbon Filter: Removes chlorine and organic impurities like harmful pesticides. It also adsorbs bad taste and odour-causing organic compounds from water.
Weight and Dimensions
The Bureau of Indian Standards (BIS) has specified requirements for removal/reduction ofheavy metals in IS:16240. We tested the 10 brands for presence of the following heavy metals:
Arsenic: As many as six brands – Tata Swach, Zero B, Kent, Aquaguard, Electrolux and Usha – did not meet the requirement (a maximum 0.01 mg/l).
Copper: None of the brands met the requirement set by Indian Standard (0.05 mg/l).
Mercuy: All the brands more or less met the specified requirement – minor deviations were observed in Pureit, Aquaguard and Usha.
Cadmium: Minor deviation was observed in one brand, Pureit. All other brands met the standard requirement.
Iron: All the brands met the requirements, with the exception of deviation in two brands, Whirlpool and Usha.
Lead and chromium: All brands met the requirements.
As per Indian Standard, an RO system shall reduce TDS level of feed water to less than or equal to 500 mg/l.
- Al brands reduced the TDS to below the limit specified (500 mg/l) when the input level was maintained at a fixed level.
- Tata Swach scored highest on this parameter, followed by Aquaguard.
- Some brands reduced the TDS level to below 100, which is also not desirable due to their reducing the intake level of essential minerals.
The turbidity of drinking water should not be more than 5 NTU and ideally be below 1 NTU. This is a key quality indicator for a water filter/purifier.
- All the brands were able to remove turbidity to a level that makes it safe and suitable for drinking.
- Kent, Whirlpool, LG and Tata Swach could remove 100 per cent turbidity and scored highest on this parameter.
- Waste water was in the range of 62 per cent–71.4 per cent. This means the recovery of water in all brands was well above the prescribed limit of 20%.
RO and RO+UV water purifiers produce a lot of waste water during the purification process. Thus, if you pass four litres of water through an RO purifier, it will produce just about one litre of potable water. All the impurities are concentrated in the waste water and hence it is not drinkable.
Can the Waste Be Used?
a) First thing: test the TDS in the waste-water stream. If the TDS is below 1,000, you can use the water in your plants.
b) Alternately, mix some of that water with tap water to mop the house. Make sure you dilute it with tap water because if the TDS is high and you use just the RO waste to mop the floor, you may see some salt deposition after the water dries.
c) You can use the waste water to clean the sewage pipe at home or kitchen because of its saline nature..
d) You can use it to flush toilets.
All the brands gave output water with agreeable taste and odour.
pH is a measure of the acidity or alkalinity of a solution. Aqueous solutions at 25 degrees C with a pH less than 7 are considered to be acidic, while those with a pH greater than 7 are considered to be basic (alkaline). When pH level is 7.0, it is defined as neutral at 25 degrees C.
As per Indian Standard, the pH of drinking water shall be 6.5 to 8.5.
Four brands – LG, Pureit, Zero B and Tata Swach – showed slight deviation from the pH requirement for drinking water.
- All the brands were able to reduce 100 per cent residual chlorine.
The presence of bacteria and pathogenic (disease causing) organisms is a concern when considering the safety of drinking water. Pathogenic organisms can cause intestinal infections, dysentery, hepatitis, typhoid fever, cholera and other illnesses. As per the BIS requirement, the RO purifier shall inactivate/kill the selected standard challenging organism E. coli.
When E. coli exceeds the permissible level in water, consumers are advised to boil the water they use for cooking and drinking, and even for brushing teeth. As per Indian Standard, the requirement is 99.9999 percentage reduction in E. coli. We observed all tested brands for four consecutive weeks to check percantage reduction in E. coli levels.
A microorganism smaller than bacteria, the MS2 virus cannot grow or reproduce apart from in a living cell. Viruses are the smallest agents of disease, and perhaps the most problematic, because they are as minute as 0.04 u (micron). Viruses cause many common human infections and are also responsible for a bevy of rare diseases. Viruses can infect all types of life forms, from animals and plants to bacteria and archaea.
Based on the requirement specified by IS: 16240,MS2 virus was spiked in input water and the output sample was tested to check the virus-removal efficiency of purifiers.
- None of the brands we tested met the requirement of Indian Standard for removal of MS2 virus. Hence, none of these RO water filters can be said to be completely safe for drinking.
- In India, high concentrations of both organochlorine and organophosphorous pesticides have been found in surface and ground water samples. Reverse-osmosis water filters are expected to remove pesticide residues.
- We tested the 10 brands for pesticide residues. They were all able to reduce the pesticide residues and scored equally well.
- In five brands – Tata Swach, Electrolux, Usha, Aquaguard and Pureit – the water-storage capacity was found to be less than the declared.
- Name of manufacturer
- Brand name
- Production serial number
- Model name or code
- Production rate in l/h
- Percent recovery of product water
- Maximum operating TDS level
- Supply voltage, whether single- or three-phase, frequency, volts and wattage
The product should include these details as well: namely address of manufacturer, manufacturing date, MRP, and warning/precaution note. An instruction manual containing proper method of operation and use of the purifier shall be supplied along with the purifier. The purifier may also be marked with the Standard mark.
All the brands had provided the required information
- All the water purifiers were packed in thick, laminated paperboard carton supported by good-quality thermocol to give protection from damage.
- In the case of Aquaguard, no manual was provided with the unit.