Kent vs AO Smith RO Water Purifiers | Which is better?



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While Kent Supreme Plus and AO Smith Z9 water purifiers try to be different in their own ways, they are excellent RO water purifiers because of their high-quality performance.

So let us compare these comparatively expensive RO water purifier brands to know which is better suited for our home environment.

Pros and Cons of Kent Supreme Plus

Kent Supreme Alkaline RO for home

One of the Best RO Water Purifiers in India that comes with a TDS Controller.


  • Good performance with 20L/hour output.
  • In-tank UV feature ensures last-minute water purification.
  • 8L storage is ideal for the average Indian family.


  • Kent’s claims of zero water wastage are not correct.
  • Maintenance and AMC costs are high.
  • The sediment filter is not available with the original package.

Pros and Cons of AO Smith Z9

Ao smith z8 hot water purifier
AO Smith Z8

Best RO Water Purifier in India that comes with a Hot Water Dispenser.


  • Good performance with the use of the latest purification technologies
  • Availability of hot water (450C and 800C) plus Normal RO water
  • 10L storage is excellent for medium and Large families.
  • The Night Assist feature is innovative.


  • The AMC (4 years) is expensive, and maintenance costs are high.
  • The water purifier is expensively priced.
Model/ParametersKent Supreme PlusAO Smith Z9
Water Purification TechnologyRO + UV + UF + in-tank UV + TDS ControllerRO + SCMT
Ideal forAll types of waterAll types of water
Can handle TDS levels up to2000 ppm2000 ppm
Water Purification StagesMultiple StageEight-stage purification
Storage Tank CapacityEight litersTen liters
Special FeaturesPatented Mineral RO technology Kent’s claims of Zero water wastageSilver Charged Membrane technology Hot water + Night Assist features
Mineral EnrichmentTDS ControllerMineralizer technology
LED IndicatorsNot availableAvailable
InstallationWall MountingWall mounting and countertop
WarrantyOne year + Extended warranty of three yearsOne-year comprehensive warranty
AMC CostsRs 4000 to Rs 5000Rs 5000 to Rs 6000
Amazon Pricing After DiscountsRs 16,199Rs 22,999

Our Verdict

Kent Supreme plus RO water purifier review

Kent is a reputed Indian water purifier brand that offers high-quality RO water purifiers. The latest models like Kent Supreme Plus come equipped with Zero Water Wastage technology that claims to eliminate water wastage. But it recirculates the rejected water into the overhead tank.

Despite this marketing jargon and high maintenance costs, the Kent Supreme Plus is an excellent performer.

On the other hand, AO Smith is a globally renowned brand. Besides RO water purification, its latest model AO Smith Z9 offers SCMT (silver-charged membrane technology) to deliver high-quality RO-purified water.

AO Smith Z8 RO review
AO Smith Z8

The AO Smith Z9 differs from its contemporary brands because it delivers hot water and normal RO water, depending on your requirements. Though this machine cannot function without electricity, its RO purification performance is excellent.

However, Kent Supreme Plus and AO Smith Z9 are expensive water purifiers.

Design and Installation

Usually, all Kent water purifiers have a similar design, with a transparent upper half of the machine housing the filters and RO membrane and the bottom half comprising the storage tank.

The tap arrangement in Kent RO water purifiers makes it ideal for wall mounting. However, many consumers have complained of weak design, making the appliance vulnerable to damage. However, you can place the machine on a stand fixed to the wall to overcome this issue.

The AO Smith Z9 has a sleek appearance and sturdy design that can be wall mounted or placed on the kitchen countertop. However, the space available for dispensing water is cramped, making filling one-liter water bottles without tilting them challenging.

The control buttons are touch-enabled, but users can get confused with them because the power on/off and hot water button options are in proximity.

AO Smith Z8 RO review
AO Smith Z8


Kent Supreme Plus delivers an excellent water purification performance because it uses a multi-stage process including RO, UF, UV, activated carbon filters, a TDS controller, and an in-tank UV feature. However, Kent does not provide the sediment pre-filter with the package. It is essential because this filter can stop prominent and visible impurities from entering the RO membrane, reducing its lifespan.

Kent claims that their machines can handle TDS levels up to 2000 ppm. Yes, they can, but the higher the TDS levels, the more water wastage.

The in-tank UV feature is innovative because it maintains the water’s purity until it is dispensed. The TDS controller mechanism is inexpensive compared to other water purifier manufacturers’ mineral enhancer cartridge mechanisms. However, it is risky if the input water source contains high TDS levels.

Kent zero wastage ro review

To eliminate TDS and other contaminants, the AO Smith Z9 uses a novel water purification method involving RO membranes and various filtering cartridges, including silver-charged membrane technology. The AO Smith Z9 lacks traditional UF and UV purification stages. But it has pre-and post-RO activated carbon filters to remove foul odor and organic contaminants.

The AO Smith Z9 is unique because it offers the facility of hot water. The mechanism is such that you can get water at 450C and 800C, besides normal RO water. It reduces the need for heating the water if required, before consumption.

AO Smith z8 hot ro

The 8-stage water purification is reportedly better than RO+UV+UF because studies show it can remove chemicals and phosphates, viruses, bacteria, cysts, particulates, endotoxins, and colloids. Silver-impregnated membranes have excellent anti-bacterial properties.

Exciting features like Night Assist, where the LED indicators glow in the dark to direct you toward the water purifier. However, the machine has drawbacks, like you cannot get hot water without power. But the 10L storage tank can dispense normal RO water without power.

Water Wastage

Water wastage is invariable in RO water purifiers because the mechanism is such that no machine can purify water without wasting water. The RO membrane blocks TDS from the source water and ejects it as heavily contaminated water through the reject water pipe.

This is better than Kent Zero Wastage
This is better than Kent Zero Wastage Mechanism

Kent zero water wastage technology recirculates this wastewater into the overhead tank instead of disposing it in the kitchen sink. Thus it claims zero water wastage, but anyone can say it is eyewash. AO Smith Z9 also wastes water, but the machine comes equipped with different membranes that reduce water wastage considerably. So compared to other RO water purifiers, the AO Smith Z9 wastes less water. Nevertheless, water wastage depends on the quality of the input water source.

Water Taste Change

RO-purified water has no taste because it is bereft of natural minerals like calcium and magnesium. The RO purification process removes these essential minerals with harmful TDS. So water purifier manufacturers use different technologies to replenish the lost minerals.

TDS of Kent Supreme Alkaline water
TDS of Purified Water

AO Smith Z9 uses special Mineralizer cartridges that leech essential minerals into RO-purified water as it passes through them. As a result, the output water becomes enriched with essential minerals, enhancing taste. The Kent Supreme Plus uses TDS controllers to reintroduce the lost minerals into RO-purified water. This process is expensive because it requires regular cartridge replacement.

The TDS controller mechanism is excellent and inexpensive, but it can be risky if the input water source has heavy metal impurities like lead, arsenic, chromium, etc.

The mechanism introduces untreated water before the UF process into the RO-purified water to replenish essential minerals. However, the UF membrane cannot stop heavy metal impurities from re-contaminating the RO-purified water.  

Storage Tank Capacity

Kent Supreme Plus offers an 8L storage water tank with an in-tank UV purification mode to maintain water purity until the dispensing stage. This innovative purification feature is unique in the water purifier industry and sets the recently introduced Kent water purifiers apart from their competitors. The 8L water storage tank is ideal for the average Indian family.

AO Smith z8 hot water dispenser

AO Smith Z9 has a larger tank with a capacity of ten liters. This tank has two separate outlets for hot and cold water. The user can receive normal RO water through the outlet on the left, whereas the right-side outlet provides hot water according to the set temperature levels. However, the water in the storage tank does not remain hot. Select the required temperature level and wait two minutes to get hot water. So, this machine does not provide instant hot water, as many believe.


The AO Smith Z9 has LED indicators indicating power on/off, water purification process, and hot/cold dispensation. Besides, the machine has a Night Assist feature with a glowing LED that directs you toward the machine in the dark. Besides, this machine has filter/cartridge/membrane replacement alarms to alert you to replace the RO membrane and other filters.

The Kent Supreme Plus does not have any LED indicators. However, it has a filter change alarm to alert users that it is time to replace the filters. Thus you get sufficient time to replace the filters on time.

Maintenance Costs

Kent offers an extended 3-year warranty with zero service charges, but the AMC and maintenance costs are high because the RO membranes and filters require regular replacement. The annual maintenance costs range between Rs 4000 to Rs 5000. An AMC is better because it includes an annual filter/membrane replacement facility. Besides, you do not pay for the regular servicing done by service engineers.

AO Smith Z9 offers a 4-year AMC for Rs 17,000 that you can take online. It is expensive because you can purchase another water purifier with this amount. However, the AMC is better than regular maintenance because the annual filter replacement costs can go up to Rs 6,000.

Some consumers have reported service-related issues like impolite service engineers attending service calls, etc. However, much depends on the individual service provider. Overall, Kent and AO Smith offer good service, but AO Smith has fewer service centers than Kent. So they depend on third-party service providers.


The AO Smith Z9 is substantially more expensive than the Kent Supreme Plus, which is also expensive compared to other contemporary RO water purifiers. However, these water purifiers offer excellent features and performance. However, the maintenance and AMC costs are prohibitive.


People looking for budget-friendly water purifier options can avoid Kent Supreme Plus and AO Smith Z98. However, the AO Smith Z9 is a good water purifier because it offers an additional hot water dispensing facility. Performance-wise, these machines are equal because they deliver high-quality RO-purified drinking water.

Vyshnavi Vanjari
Vyshnavi Vanjari
Vyshnavi Vanjari, an Analytics Engineer at Straive, has a Bachelor's degree in Electronics and Communication Engineering, and she's been awarded a gold medal for her achievements. She's skilled in technical know-how and writing and loves sharing her expertise on topics like ceiling fans, BLDC technology, and electronic appliances.


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