Choosing a Water Purifier

I purchased an Aquaguard iNOVA UV purifier in 2004, and now after nearly eight years it was time to change it. No maintenance has ever been carried out on the Aquaguard, even though based in Bangalore, no one from Aquaguard had ever visited in the last 8 years to service the water purifier, including the period it was under warranty. The purifier happily churned out 'purified water', I do not know how effective it was in purifying water, since none of the internal components had ever been serviced or changed in the last 8 years. However, the lights on the Purifier have always turned from red to yellow to green when switched on, which according to Eureka Forbes, indicates everything is good to go and purified water flowing from the Aquaguard was safe to drink. The only thing that did stop working was the music, the device decided to stop playing music when the water flowed after a few years.

So I began to do some research on the types of purifiers available in the market today. The most popular purifier manufacturers appeared to be Kent, Zero B (Ion Exchange), Aquaguard (Eureka Forbes) and Pureit (Hindustan Unilever). Others available included Philips, Whirlpool, Tata and Nasaka.   It also seemed that Reverse Osmosis (RO) purifiers were becoming more popular, even though they were much more expensive than the UV filters,  usually costing more than twice the  price of the most expensive UV filters.

I initially shortlisted Kent and Zero B, Kent had  the most print and TV ad presence. Hema Malini and her daughters extolling the virtues of Kent frequently made appearances on TV ad spots and in full page colour ads in mainstream magazines. Zero B was made by a company (Ion Exchange) that was an old name in the water purification business.

I first needed to decide whether to go for another UV based purifier or go for an RO based purifier. My research indicated that UV purifiers could remove bacteria and viruses but not other contaminants like nitrates, arsenic, fluorides, mercury etc.. Also, UV filters would not reduce the amount of total dissolved solid (TDS) in the water.  The most logical thing for me to do would be to get my water tested (which is a combination of corporation water and bore well water) and see whether it did contain any of the contaminants like insecticides, pesticides, nitrates, arsenic etc. to warrant an RO purifier. I did call up a couple of Water testing laboratories and they they said they could do water testing and give a report in 4 - 5 days. But lethargy prevented me from doing so, however I did purchase a TDS meter, an  HM Digital TDS-3 for around Rs.800/-. The TDS meter indicated that my water had a TDS content of between 250 - 300, the readings varied on different days, I presume based on the quality of the water being supplied.   

I decided to go in for an RO bases purifier, even though literature on the internet indicated that there was not need to go in for an RO purifier if the TDS was less than 500. However, since I did not know the nature of the contaminants in my water supply, I decided it would be safer to go for a RO unit rather than a UV based unit.

I requested for a home demo from Kent and Zero B, a salesman from Zero B arrived within a couple of days, checked the TDS which indicated a count of around 300 and then proceeded to demonstrate the impurities in both the tap water and the Aquaguard filtered water by dipping electrodes (he told me the rods were aluminium and iron) in both samples of water, and when the power was switched on after a few seconds gooey frothy brown stuff magically collected on the surface and at the bottom of the two glasses. Impressive. However, when I asked him what the brown stuff was, he just said they were impurities. He could not provide any detailed explanation of  what it was. I searched on the internet but could not find any further information. So it was inconclusive, I have no idea what reaction the electrodes caused, whether it was of any significance or whether the demonstration was part of a snake oil salesman's sales pitch. The two photographs below show  how the water looked after electrodes were put in the tap water and Aquaguard filtered water.

The Kent RO Purifier was a RO + UF +UV  purifier, therefore theoretically provided the best of both worlds. The RO membrane would get rid of all the contaminants and the UV filter would get rid of the viruses and bacteria that were not removed by the RO membrane. The Zero B purifier had a seven stage purification method, with 4 stages of purification before going through the RO membrane. This appeared to be a plus point to me, since only filtered water would go to the RO membrane, unlike the Kent RO models where tap water was going directly to the RO membrane.


The Kent RO schematic in the image below shows that raw water goes directly to the RO membrane without any filtering which would potentially reduce the life of the RO membrane increasing ongoing maintenance costs.

Kent RO Schematic

The Zero B approach appeared to have a more effective design as only filtered water was processed  by the  RO membrane resulting in a longer lasting RO membrane, also the Zero B purifier has an auto flush mechanism for the RO membrane, cleaning it periodically which would enhance the life of the RO membrane. However, the Zero B purifier had no UV filter, so I wondered how effective the other 6 filters on Zero B were. Were they better than or equal to UV treatment of water. So though I was leaning towards the Zero B purifier, I was still undecided.

I then remembered a news report that had appeared a few years ago where a Government agency had carried out tests on several Indian water purifiers and only very few had passed the test. So I decided to see if I could locate this report. After scouring the net, I was finally able to locate the report. The test had been conducted by the National Institute of Virology (NIV), Pune and was published in the August 2009 issue of 'Tropical Medicine and International Health' journal. The link to the report is Virological evaluation of domestic water purification devices commonly used in India.

 

The 8 units that had been reviewed were :

Model reviewed                  Company           Price (Rs.)  Log Removal Value

Unit 1 - Iodine Resin filter    Zero B               295            2.20

Unit 2 - Dual Filter            Eureka Forbes       6750            2.51

Unit 3 - Filter + Chlorine      Orpat               1750            1.52

Unit 4 - Filter + UV            Krystalle           2990            1.45

Unit 5 - Carbon + EICD          Eureka Forbes        690            1.70

Unit 6 - Polyester + Carbon     Anjali B             205            0.21

Unit 7 - Hollow fibre membrane  Aqua Plus           5900            6.53

Unit 8 - Gravity fed filter     Hindustan Unilever  1800            6.53

The institute checked the purifiers for removal of the Hepatitis E virus, and only units 7 & 8 managed to remove all viruses during the purification process. All the other units only managed to partially remove the virus to varying degrees after purification.  The Zero B filter removed removed 2.2 log which wasn't too bad, since in the Zero B RO system that I was considering, the Iodine filter was filter number 7 and presumably the other 6 filters would remove the viruses.  What surprised me was the lack of effectiveness of the UV filter by Krystalle (only a 1.45 log removal). The Krystalle UV purifier uses an 8 watt UV lamp (see link). The UV filter tested was by a relatively unknown manufacturer, but still the lack of effectiveness of UV was a surprise. Since a specific UV strength is required to destroy different micro-organisms, I had no idea whether the 11 watt UV light on Kent RO+UV system was sufficient to provide the required micro watts seconds per centimetre squared to effectively kill all micro-organisms. See the following link for UV dosage required to kill micro-organisms - UV light to destroy micro-organisms Since I was considering the Kent RO + UV purifier, there was no specific literature on the Kent website, regarding the efficacy their UV filter against specific  bacteria/ viruses and because tap water was going straight to the RO filter, which would in all probability reduce the life of the RO filter which is the most expensive component in RO filters which needs to be replaced periodically, resulting in increased maintenance costs, I decided remove the Kent UV + RO filter from my shortlist.   

Since the review by NIV indicated that Hindustan Unilever's Pureit Gravity fed filter was successful in removing the all the Hepatitis E virus during the purification process , I added the Pureit water purifiers to my shortlist. Pureit was cheap, required no electricity  and out performed the other more expensive units. However, since the Pureit gravity fed filter would not reduce TDS or other contaminants, I shortlisted the Pureit Marvella RO water filter. The HUL website does mention that 'Each Pureit device meets USA Environment Protection Agency’s (EPA) stringent germ kill criteria which recommends log 6, log 4 and log 3 reduction of harmful bacteria, viruses & disinfectant resistant parasites respectively' and the NIV test did confirm a log 6 reduction in the Hepatitis E virus for the Pureit Classic model. The NIV test did only check efficacy against only one Virus, but at least the Pureit purifier passed it.

Now what does log 6, log 4 and log 3 reduction represent?. My research led me to understand that log values are used in the water treatment industry to express the level of removal of biological contaminants from water. A 6 log reduction represents a 99.9999% reduction in contaminants, a 5 log reduction represents 99.999% reduction, a 4 log reduction represents a 99.99% reduction and a 3 log reduction represents a 99.9% log reduction in contaminants and so on an so forth.

The US EPA standard for removal of pathogens from water requires removal of bacteria, 6 logs (i.e. 99.9999%) or better, viruses, 4 logs (99.99%) or better and parasites, 3 logs (99.9%) or better. HUL mentions that all its Pureit products meet the above standards and the NIV test confirms a 6 log removal of the Hepatitis E virus. None of the competing manufacturers mention this in any of their literature or on their websites, or if there is any information on this I could not locate any information. The Kent site indicates that they have WQA Gold certification. But what did this Gold Certification represent? Visiting the WQA site shows that Kent does have certification for RO systems for reducing very specific set of contaminants (barium, fluoride, lead nitrate, nitrite, Pentavalent Arsenic <= 50 ppb reduction, TDS, with the caveat that the 'System tested and certified with raw water bypass (control) valve in the closed position. TDS reduction will vary if the TDS control valve is open. Nitrate & Nitrite reduction claims are only valid with the TDS bypass control valve closed so that the full TDS reduction is in effect'), which basically meant that if the TDS control valve is open, the efficacy of the purifier would be compromised.  The link to the WQA site is  Kent WQA certification but there is nothing on virus, bacteria, and parasite removal. This provided me further affirmation that my decision  not to consider the Kent RO purifier was correct.

So as a result of all my research I decided to go for the HUL Pureit Marvella RO unit. Although, the model I was considering purchasing was not the one reviewed by NIV, the HUL literature on their website confirmed that all Pureit models met US EPA's standards. Also, like the Zero B model the water  passed through filters before going through the RO membrane.


Pureit Marvella RO Schematic


The tap water passed through 3 filters - a pre-sediment filter, an activated carbon filter and a post sediment filter  before being going through the RO membrane. Since water was being processed by the RO membrane only after passing through 2 sediment filters this would  increase the life of the RO membrane and reduce ongoing maintenance costs. Also, my research on the internet indicated that an activated carbon filter before the RO membrane traps organic chemicals and chlorine, which can attack and degrade reverse osmosis membranes (see wikipedia link). In the Pureit RO purifier, as you can see in the diagram above, water has pass through the activated carbon filter before the reaching the RO membrane.  The Pureit RO purifier has an advertised  800 hour life span for the RO and UVM membranes and 400 hour life span for the Carbon and sediment filters.  An 800 hour life span of the RO membrane, meant that the RO membrane should last me for at least 2 - 3 years.

The Pureit Marvella RO unit was also cheaper than the Kent Grand + (list price Rs.16500) and Zero B Emerald (list price Rs. 15990) purifiers, with a list price of Rs. 13500 which I was able to get for Rs. 12500.

So I did purchase the Pureit Marvella RO water purifier and it appears to be working well. A TDS check on the water post purification is less than 25. Only time will tell whether there will have any problems with the purifier and will update this page give an update on any issues faced.

Long term Use Update (9th May 2013) : I have now been using the Marvella RO purifier for more than a year, around 13 and a half months. It have been uneventful, the purifier has been working without any issues and I therefore have not had the opportunity to evaluate the quality of their service, either for fixing a problem or for replacing any of the cartridges. A TDS check on the purified water shows a TDS reading of less than 25 ppm.  I will update this page, when I do have to call service either to change the cartridge or fix a problem, and report on the quality of the service provided.
 

Long term Use Update (7th November 2014) : A couple of days ago, the purifier outlet pipe began dripping water even after the purifier tank was filled up. I called up the Marvella customer service number and they said a technician would come to repair the purifier within 48 hours. The technician came the next day and said the solenoid value needed to be changed. The cost of replacing the solenoid value was Rs. 650/- and the service charge was 250/-.Therefore I spent a total of 900 rupees for changing the solenoid valve which fixed the leak problem. While he was there I asked him what cost of the taste modulator. He said it would cost Rs. 800/- .  I decided to get the taste modulator fitted just to try it out.The taste modulator was fixed on the next day. Don't notice much change in the taste of the water.

Photograph of the faulty solenoid valve which was replaced :