Monday, August 27, 2012

Kent Pearl RO Water Purifier Review

Hello n Good Day!

     Having used the Kent RO water purifier (Pearl) for over 18 months, I have learnt a lot about the RO filtration system in general; what to expect and what not to, how to avoid disappointment and frustration, and to save lot of money in spares and maintenance. so here I am writing this blog sharing things i have learnt the hard way.
Grab some coffee, this is going to take a while!

The Good News! if you have decided to go for Kent Pearl water purifier, congratulations you have made a credible decision! This is a quality product and it delivers what it promises; Pure Water! Kent Pearl is one of the top model, which I prefer over others in its price range.

Disclaimer: the intent of this article is to make you aware of what to expect in a water purifier, particularly a RO (Reverse Osmosis) type. By no means this is a recommendation of any sort.
Do your bit of research before making a choice.

I am starting with a quick look at the features of the Kent Pearl RO water purifier, pros and cons. Then talk about what to look for before buying a RO purifier, how RO purifier works, what is it made of, stages of filtration, service, maintenance and spares.

Review model : PEARL  


Purification by RO membrane and UV, with TDS control.
kent pearl
  • Automatic start up and stop.
  • Detachable storage tank for easy cleaning.
  • 8 Liters storage capacity. 
  • Computer Controlled Operation with Filter Change Alarm & UV Fail Alarm.***
  • Purification Capacity - 15Ltrs/Hour (at room temperature and 750 PPM of water) ****

Other features claimed is a "Computer Controlled Operation with Filter Change Alarm & UV Fail Alarm." - well there is no computer or microprocessor used in the purifier control circuit board. Just a marketing gimmick!.

After about a year or so of use the alarms go "beep beep beep"!! it sounds for a minute or so when the filter is powered ON and then everything is normal.  another gimmick to fool consumers to believe that something is wrong  and to buying a new control board!
I had new filter spares installed at about 10 months of use (my water is very bad) that's 2 months prior to alarms turning ON! clearly the so called computer control (which actually isn't there) couldn't tell that i already have replaced new filters.

update : 24 Dec 2015. see the video on how to reset the alarm at the end of the blog.

Purification Capacity - 15Ltrs/Hour (at room temperature and 750 PPM of water) - well this is just a manufacturer claimed specification just like the claims you have seen for a 2-wheeler mileage.
Practically it takes a bit close to an hour to fill that cool looking 8 Litres storage tank.

For a detailed feature and specification see the manufacturer website

  • Delivers pure water as promised.
  • The build quality is very good. food grade plastic been used.
  • Transparent & Detachable storage tank for easy cleaning.
  • Automatic start up when water level is low and automatic stop when full.
  • Can be placed on table or put on the wall.
  • Elegant look.
  • 1/4 inch quick fit connectors, which is simple to connect and disconnect, in case you want to do some maintenance yourself or clean the pre-filter.
This purifier will go on for more than a year without any service or filter spare replacement if TDS of your water is <500 PPM and or the usage is minimal.

The only negative about Kent or any other manufacturer for that matter? you guessed it right  
"After sales service"
This is where the trouble begins and dampens the reputation of a brand. and the common perception "Oh that brand is bad". and the sad thing is that manufacturers do nothing about it!

Any reputed brand of water purifier will do its job, its only a matter of choice, service and maintenance to look for.

Before you buy a RO water purifier:
  • Choose your brand. why go for a brand? that's because its a matter of trust. A good brand will have quality parts and reliable performance.  
  • TDS Meter pen type
    Purifier stages; you would have noticed manufacturers claiming stages of purification ranging from 5 to 10 and beyond. Make sure your choice of purifier must have a RO membrane, UV and TDS control. the rest of the other claimed stages will fall in place; no need to worry about how many stages.
  • Water purifiers with RO, UV and TDS control are usually the top end models and do cost more, you also have the option to choose a RO only model (without UV and TDS control)
  • while the RO only model removes all the germs and dissolved salts, it better to have UV which will further eliminate germs that can build up inside the membrane, because there always will be some water in the membrane standing still when the purifier is at rest.
  • Call for a demo. check your water for the TDS measurement.  Most RO purifier will work fine up to a TDS of 1000 or more. (update 30 Nov 2015: this is just a manufacturer claim, i have seen the RO membrane fail in 3 months with a TDS of about 600) also check if the pressure of water is sufficient; sometimes if you are living in the top floor pressure is likely to be a bit less. RO purifiers work under pressure, so some purifier may not even start when the pressure is below a minimum requirement.
  • Also when you are installing your purifier, insist the service engineer to open up the RO membrane housing and visually check the RO membrane side wall it should look white like new! - newer models may come with sealed membrane houseing to prevent tampering.
    sides of the membrane white and new!
    image courtesy

Pre-filter housing
  • Install a pre-filter.
Although optional, its always wise to install a pre-filter. A pre-filter is an external attachment that filters suspended particles like sand, dirt & rust etc present in the inlet water. This also increases the service life of the filters.The cartridge inside its housing collects the suspended particles. its cheaper to change the pre-filter cartridge and you need to change it every 2 to 3 months (depending on water quality)

pre-filter is installed close to water inlet. and the water purifier right next to it.

Maintenance :

Like with any electrical or mechanical system, you water purifier needs regular maintenance. Sediment filter and Carbon filter needs to be changed every 12 months or so. sometimes you need to change them earlier depending on the daily usage and the quality of water.  Pre-filter  cartridge (or PP filter, called otherwise) need to be flushed every few weeks, over time (2-3 months) the PP filter clogs up and needs to be replaced.

       Should you notice that the water output of the purifier has slowed down, its more likely that one of the filters need replacement. changing the filter on time saves your "RO membrane", the hero of the purifier system. A RO membrane should last about 2 - 3 years, again this depends on the usage, the quality of inlet water and the quality of the RO membrane itself.

       Reject water; this is the waste water that is rejected during the purification process. Reject water has a high concentration of salts and is not suitable for drinking . you can drain it or use it for cleaning and washing. Reject water keeps flowing all the time when the purifier is working. if there is no reject water flow, the "flow restrictor tube" has failed. call the service engineer immediately and get it replaced otherwise this will result in premature failure of the RO membrane.

Note that for every liter of product water (purified water) there will be about 3-4 liters of reject water; this is normal with any RO purifier.
  • When there is a need to replace a filter consider replacing both the sediment and carbon filters at the same time because if one fails the other is likely fail as well.
  • Usually your purifier is covered by a 1 year warranty for the RO membrane and filters. some manufacturers provide only a 6 month warranty on filter spares. so its advised to service your purifier around 5th months of use, while its still under warranty and save your self money.
TDS Meter: It's a good idea to keep a TDS meter handy. Keep a check on TDS of your drinking water atleast once in a month. If the TDS of the inlet water has gone up (assuming you buy water from different sources) more likely the TDS of your purified water would have gone up as well.

Please read on to know more about how the quality of your water affects the life of the Purifier. This may also serve as a guide to choosing your water purifier.

You should know this!

You probably know water as either soft water ( municipal tap water) or hard water (well, bore well)
but there is one more thing you need to know, TDS of water.
TDS is Total Dissolved Solids in the water and is measured in PPM (parts per million or ml/Liter)
It is expressed as a number eg 750PPM. the higher the number the higher the hardness, meaning more dissolved salts and minerals that are undesirable and unhealthy. To name a few dissolved substances; calcium, magnesium, sodium, phosphor, nitrates, chlorine.
There are also bacteria and viruses that can cause illness and must be removed.

The common UV filters you know, only removes suspended particles like sand and dust. they remove chlorine often found in treated municipal tap water. the UV kills bacteria and virus but not all. the rest of the dissolved substance still remain in the water and we drink them! to completely remove these contaminants you need a RO purifier.

A RO (reverse osmosis) water purifier uses a RO membrane that removes the dissolved salts and minerals and completely eliminates bacteria and viruses. the membrane is made of multiple layers of thin sheet with tiny pores in it, rolled and cased inside the membrane housing. (see video at the bottom of the page) The pores are so small even viruses are blocked and removed. only water molecules pass through the membrane that is free of salts and germs.

MF = micro filtration   UF = ultra filtration
NF = nano filtration   RO = reverse osmosis filtration

TDS control; remember the RO membrane will remove all the salts (up to 98%) present in the water. in the process some useful salts (minerals) are also removed, so it is necessary to add them back,TDS control will do just this. Along with the RO membrane, a good purifiers will also have a UF membrane (UF - Ultra Filtration membrane) that just like the RO membrane filters out germs but allows only useful minerals to pass through; this water is then mixed with RO membrane output water to add back minerals. the TDS control valve lets you adjust the required quantity of useful minerals. A TDS meter can tell how much useful minerals have been added back. Some purifiers are equipped with a mineral cartridge in the final stages to add more minerals and these will be marketed as mineral RO purifier just to make a few extra bucks!

Please note, the minerals in question are found in water only in trace (very less) amount. Pure RO water will be crisper with no taste. presence of minerals adds taste to water.

Here is a quick look at the TDS scale

The service engineer will usually set the TDS of your water purifier anywhere between 50 and 100ppm.
Bottled water usually have a TDS set at ~25ppm.
Bottled mineral water will have a TDS around 200ppm or more. This sound a lot but these are essential salts.

Fun test : requirements; RO water purifier, a cup, TDS meter and common salt.

1. take a cup of RO purified water, note the TDS.
2. add a pinch of common salt to the glass of water.
3. Measure the TDS!

Filtration Stages:

I am listing the most basic and important stages required. though some manufacturers may introduce one of more stages here and there, giving them fancy names to grab your attention.
Stages are placed in the order water is treated. water goes to stage1 and then to stage2 an so on
  1. Pre-Filter; this stage is optional, but good to have as discussed earlier.
  2. Sediment Filter; removes suspended particles that were left behind by pre-filter or does the same job as pre-filter when this is the first stage.
  3. Pre-Carbon filter; removes chlorine and organic compounds. germs pass through!
  4. RO membrane; removes dissolved salts and germs.
  5. UF membrane; removes germs but allows some useful salts. please note that some purifiers don't use this membrane, rather they divert water output of the pre-carbon filter (with germs, that will be killed in the UV stage) and mix it with RO water output.
  6. TDS controller; this is just a valve that controls how much water from the UF membrane or pre-carbon filter gets mixed up with water output of RO membrane to add back some useful salts.
  7. Ultra Violet chamber(UV); water from the RO and UF membrane (or pre-carbon) are further processed with UV light to kill (De-activate ) the left over germs.
  8. Post-Carbon filter; similar to pre-carbon, removes chlorine and odour and makes the water taste better.
Water finally passes on to storage tank for consumption.
Besides these various components there are others that make up you RO water purifier;

Booster pump; used to boost the inlet water pressure. RO membrane works under pressure because you have to force water through the tiny pores in the membrane that we talked about earlier.
Pressure Switch; used to turn on the booster pump only when there is minimum working inlet water pressure.
Solenoid valve; used between pre-carbon filter and RO membrane inlet, solenoid valve shuts off water inlet to the RO membrane when inlet water pressure is low and or the tank is full. this reduces pressure on the membrane when its at rest.
Flow restrictor tube; this is a small valve placed on the reject water outlet of the RO membrane housing. its job is to let out reject water at a fixed flow rate. this ensures optimal pressure inside the RO membrane housing. 

there is also a power supply unit powering the control circuit board which controls the functioning of the entire system; sensing the inlet pressure, turning on the booster pump and solenoid valve, powering the UV lamp chamber, sensing the storage tank for water level, and shutting off the pump when the storage tank is full.

here is a schematic showing how the various stages are connected, please note this will vary with different manufacturers.

A typical RO purifier system
image courtesy:
When to call service
  • You better take advantage of the warranty period, most branded purifiers come with  a 1 year warranty. sufficiently long time to evaluate your purifier and fix faulty parts.
  • Make sure the service engineer reaches your place earlier in the day, so he is fresh and has all day to fix your purifier.
  • Call service around 5th month and 10th month just to do a routine check on the health of the purifier.
  • Call service if you feel the drinking water output has slowed down. you can do this by noting the time it takes to fill or by visual check, that's why go for a transparent and detachable storage tank.
  • Call service if you feel the reject water output has slowed down or stopped altogether.
Installation & Service gimmicks!

Installation and Service are two extremes and always opposite, here's how

Installation attitude ; Super fast, done same day, happy to serve, call me anytime - No problem. Here is your bill. Thank you!
Don't forget to get your warranty stamped. Always buy from a authorised dealer. The guy who installs will not show up again. his job is done. His target is to install the thing. He wouldn't care to suggest you things like a pre-filter or a water pressure booster when its most needed.

A pre-filter is optional, installation will go through even without it. why would he bother to save your money. perhaps the idea is to make more money out of spares. you only realize that your sediment and carbon filters have clogged up and prematurely failed because your water is so bad, only a pre-filter could have saved them.

Insist on a pre-filter installation, this might cost you a bit more but its worth it. you can also buy it on eBay (I miss ebay) amazon for much less than what the dealer charges. its a good idea to buy it upfront and ask the installation guy to fix it for you. or you can do it with the help of a plumber.

Water pressure, is a bit less on the top floor of the house. with such low pressure the purifier may sometimes not even start. to avoid this the installation guy usually tries to disable the pressure switch. what happens is the booster pump keeps running even when there is low pressure or no water at the inlet. this will ruin the pump and also since pressure is less the water output will be slow and will take lot more time to fill the storage tank.

Make sure to check if the pressure switch feature works. how to check? An inlet valve will usually be installed on the inlet water pipe. simply turn off this valve while your purifier is working, purifier should stop in a few seconds! and should start back once the inlet valve is opened.

Make sure the TDS of your purifier is set in the range of 40ppm to 80ppm.

Service attitude ; super slow, usually not done in a day, happy to serve more spares, call me anytime (but i may not be available), I'm done for the day. here's the bill for spares. Good Bye!

Usually 9/10 times a lousy service engineer ends up at your door. He seems to know only as much required to get your water purifier working. Recall that i mentioned about having the service engineer reach your place early in the day? That's because you buy more time for him, just in case he finds that a spare is not available in his service kit right away and it has to be procured from a warehouse located else where. so you at least can hope the he gets the spare and your purifier will be fixed the same day.

Service engineers who attend your service request late in the day usually try to give excuses, they are human after all, tired after a long days work, they try to run away without fixing your purifier, promising to return the next day. They usually don't show up and you end up calling them again.

Beware!  Any faulty part needs to be replaced with a new one. A service engineer in a hurry might bypass faulty parts compromising the very purpose of your water purifier.
for eg a sediment filter can be bypassed by connecting its inlet and outlet together thus removing the sediment filter stage! the same can be done for any stage!.

Sometimes they replace faulty parts with used spares, they do this usually during the warranty period since they have to bear the cost of spares. you can visually inspect the spares by looking into the inlet and outlet and it should be clean like new. used spares will have muddy/dark deposits in the inlet and outlet.

A note on spares: This is where manufacturers and service provider make lot of money. Spares are usually sold at unreasonably high cost! Go for a purifier with 1/4" QC (1/4 inch Quick Connect) fittings, this is usually the standard for domestic RO purifiers. there are lot of suppliers who make filter spares for 1/4" QC fitting. You can buy then online for less price! These spares will just work as good as the so claimed genuine ones if not better.

video on "Quick Connect fitting"    

Reader's videos:

How to reset the timer alarm : Thanks Prakash. this is helpful. (24 Dec 2015)

Please do your research and compare, see how your choice of RO water purifier fares and then make your decision. That's all I have to say.

Hope this was useful. Please share and educate people you care for. Thanks.
Good day!

30 JUN 2014
A request: please ask your questions in comment section at the bottom of this blog page so others benefit too. i may not answer questions sent to my inbox, sorry about that :)

Also, some of the common questions are already answered in reply to comments from other readers. please search this blog to find what you are looking for.

don't find it yet? go ahead and ask in the comments, I will be glad to answer. 

11 Aug 2014

Here are some pictures of kent membrane housing and carbon filters pried open. Thanks Mukesh for sending these in

RO housing and membrane. DOW Filmtec membrane the best in business!

carbon filter

update: Nov 30 2015 10:15am

important buying decision
1. if you are spending around 15000 INR or more, make sure to get a purifier with RO +UF+UV. there are some models without UV but been sold at the same price as models with UV!
2. Don't buy purifiers with fixed and opaque tanks.

update : 02 DEC 2018

After many years of using ebay/amazon bought UF membrane I figured out all the UF membrane sold online is a FAKE!! Those UF membranes are just sediment filters.

If you need to buy a genuine hollow fibre UF membrane 

buy this one

 I bought one and its genuine. you could actually see the hollow fibre tubes on the side
buy on amazon

Thank you for all the appreciation and thank you for taking time to read this story, this only show you care about your health!

If you are serious about your health and concerned about medicine and its side effects, there is one person you need to hear from, a cardiologist revealing the ugly side of scientific medicine!

go here >

We are spoilt for choice in this modern times, if you chose health, you chose wisely.

$('#comments p a').hide());