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How the order is set. The top three slots are named picks — best overall, most popular, best value — and each states the measurement it won on. Every product after them is ordered by one fixed formula: the Amazon star rating and review count, applied identically. No brand can pay for a slot, a badge or a score.
We do not test products in a lab. Read the full method on How We Rank.
1
What 4,035 buyers talked about
“Hoped that this was going to be easy to use, easy to install, great tasting water!! And it was and is!!!!!”
2
Amazon's Choice
What 1,047 buyers talked about
“This was very easy to install and the UV light to kill viruses is a game changer.”
3
What 669 buyers talked about
“Great product - very easy to use - and the water tastes great! Finally some relief from plastic.”
4
Amazon's Choice
What 318 buyers talked about
“Great tasting water! And a well designed system. Very slick.”
5
What 2,453 buyers talked about
“Great system, my water is much cleaner now. Easy to install.”
6
Amazon's Choice
What 1,649 buyers talked about
“Easy install and good product support. We moved into a new house and just didn't like the water.”
7
Amazon's Choice
What 15,076 buyers talked about
“Easy install, great water, and even better customer service.”
8
What 3,635 buyers talked about
“This water filter makes great tasting water. It's easy to setup and use and easy to maintain.”
9
What 268 buyers talked about
“Water tastes so fresh and clean. No chemicals and no after taste just fresh clean water. Worth every penny.”
10
Amazon publishes no review themes for this listing, so there is nothing here to count.
Why trust this list
Every ranking below is a count, not an opinion. Here is the size of the sample behind this page.
WinnerReviews counted 1,557 mentions of leaking across the reverse osmosis systems on this page and only 29% of them were positive — the complaint shows up for Waterdrop, iSpring and SimPure alike. These units sit under a sink at mains pressure with several push-fit joints, so a slow leak is both the most common failure and the most expensive one. Whatever you buy, fit it where you would notice water, and check the joints in the first week.
453 of 1,557 mentions, 3 brands
Tankless systems trade the storage tank for a booster pump that runs each time you draw water. WinnerReviews found noise mentions for Waterdrop split almost evenly at 52% positive across 229 mentions. A tank system is quieter but takes up most of the cupboard; there is no option here that is both silent and compact.
119 of 229 mentions
The purchase price is not the price. Replacement filter sets are due every six to twenty-four months depending on the stage, and WinnerReviews found value-for-money mentions ran only 63% positive across 344 mentions on the systems where buyers raised it. Price the filter set before you buy the unit, not after.
218 of 344 mentions, 2 brands
This is the one that costs real money. Across the systems on this page we counted 1,557 mentions of leaking and only 29% were positive, and the complaint was not confined to the cheap end — Waterdrop, iSpring and SimPure all appear in it.
| Brand | Share of mentions that were positive | Sample |
|---|---|---|
| SimPure | 15% | 23 of 158 |
| iSpring | 30% | 361 of 1,194 |
| Waterdrop | 34% | 69 of 205 |
Under-sink systems hold mains pressure across several push-fit connections, and a joint that weeps rather than bursts can run for weeks behind a cupboard door before anyone notices. If the cabinet sits above a finished floor or a downstairs room, that changes what you should buy: a countertop unit holds no pressure and cannot flood anything. If you do go under-sink, run it for a week with a sheet of paper under each joint.
The 400, 600 or 800 GPD figure on the box is the membrane's daily throughput under ideal pressure and temperature. It tells you almost nothing about how fast your glass fills.
What governs that is whether the system has a tank. A tank system stores a few litres at low pressure and delivers them quickly, then needs time to recover. A tankless system filters on demand — no waiting for recovery, but the flow is whatever the pump can push, and it runs while you pour. Neither is faster in every situation, so pick on how you actually use water rather than on the largest number.
An RO membrane does not distinguish between contaminants and calcium. It strips almost everything, which is why RO water tastes flat to some people and why the question of whether it leaves you thirsty comes up so often.
The fix is a remineralising stage, sold as "alkaline" or "AK" on these listings, which adds a small amount of mineral back after filtering. Several systems here include it. It changes taste more than health — a normal diet supplies far more of these minerals than drinking water does — but if flat-tasting water would stop you using the thing, pay for the stage.
Every RO system produces wastewater: the concentrate that carries away what the membrane rejected. Older systems sent three or four litres to the drain for each litre they filtered. The tankless systems on this page are much better, typically quoted between 1:1 and 3:1.
It is worth knowing before you buy, both for the water bill and because it means an RO system is the wrong tool for filtering everything in the house. Plumb it to the drinking tap, not the whole supply.
A multi-stage system has several cartridges on different schedules — sediment and carbon stages every six to twelve months, the membrane every two years or so. Miss them and flow drops, taste returns, and the membrane fails early.
Add up a full replacement set and multiply by three years before comparing two systems. We found value-for-money mentions ran only 63% positive across 344 mentions, and running cost is where that disappointment usually comes from rather than the purchase itself.
One block per product, built from the review themes Amazon publishes for that listing. We do not test these — every figure below is a count of what buyers wrote.
Positive 85%3,176 comments counted
Every theme Amazon counted
Hard to find a real complaint. 85% of 3,176 counted comments were positive, and 580 of the 613 who brought up quality were happy.
The one place it slips is leakage, at 35% of 144 comments. Worth knowing, not worth walking away over.
What people actually talk about most is installation — raised 728 times, positive 93% of the time.
Honestly, if you asked me which one to get, this is it. Nothing in the 3,176 comments we read comes back as a real complaint — and that is rarer than you would think at #1 on a WinnerReviews list.
Positive 78%850 comments counted
Every theme Amazon counted
A solid pick that comes with an asterisk. Leakage drew 41 comments and only 29% of them were positive.
The rest holds up. Water quality is the standout at 95%, and across all 850 counted comments 78% were positive.
Here is how I would put it: get this one if water quality matters more to you than leakage. That is the whole trade, and it is why WinnerReviews has it at #2 rather than higher.
Positive 79%510 comments counted
Every theme Amazon counted
Most people get on with this one. Where they do not, it is durability: 24% positive out of 21 comments.
Set that aside and it looks strong — ease of use at 94%, and 79% positive over 510 comments in total.
The busiest thread is water quality: 137 comments, 89% of them positive.
Worth buying with your eyes open. It is genuinely good at ease of use — just do not expect much on durability, because 76% of the people who brought it up were not happy.
Positive 83%344 comments counted
Every theme Amazon counted
This one comes through clean. Of 344 comments spread over 8 themes, 83% were positive, with water quality the clearest strength at 95%.
Leakage is the softest spot at 30%, on 20 comments. Nothing that should change your mind.
One caveat on all of the above: 318 ratings is a small base, so these percentages can move a lot on a few hundred more.
Buy this one and stop reading. Water quality is where it shines, the rest holds up, and after 344 comments we could not find a reason to talk you out of it.
Positive 92%2,046 comments counted
Every theme Amazon counted
Hard to find a real complaint. 92% of 2,046 counted comments were positive, and 369 of the 377 who brought up quality were happy.
The busiest thread is installation: 495 comments, 93% of them positive.
This is the safe answer. We went through 2,046 comments looking for the catch and never found one, which is why it sits at #5.
Positive 87%1,717 comments counted
Every theme Amazon counted
This one comes through clean. Of 1,717 comments spread over 8 themes, 87% were positive, with value for money the clearest strength at 97%.
Leakage is the softest spot at 45%, on 94 comments. Nothing that should change your mind.
For what it is worth, quality is what comes up most — 402 mentions at 96% positive.
Buy this one and stop reading. Value for money is where it shines, the rest holds up, and after 1,717 comments we could not find a reason to talk you out of it.
Positive 89%13,709 comments counted
Every theme Amazon counted
Hard to find a real complaint. 89% of 13,709 counted comments were positive, and 1,187 of the 1,200 who brought up water quality were happy.
Leakage is the softest spot at 29%, on 1,100 comments. Nothing that should change your mind.
For what it is worth, installation is what comes up most — 3,000 mentions at 90% positive.
Buy this one and stop reading. Water quality is where it shines, the rest holds up, and after 13,709 comments we could not find a reason to talk you out of it.
Positive 85%3,937 comments counted
Every theme Amazon counted
Hard to find a real complaint. 85% of 3,937 counted comments were positive, and 645 of the 693 who brought up quality were happy.
Leakage is the softest spot at 10%, on 143 comments. Nothing that should change your mind.
For what it is worth, water taste is what comes up most — 869 mentions at 89% positive.
Buy this one and stop reading. Quality is where it shines, the rest holds up, and after 3,937 comments we could not find a reason to talk you out of it.
Positive 84%306 comments counted
Every theme Amazon counted
Buyers are unusually united on this one. Across 306 comments Amazon has grouped into 8 themes, 84% were positive — and the strongest, convenience, ran 12 happy out of 12.
Leakage is the softest spot at 53%, on 15 comments. Nothing that should change your mind.
One caveat on all of the above: 268 ratings is a small base, so these percentages can move a lot on a few hundred more.
Buy this one and stop reading. Convenience is where it shines, the rest holds up, and after 306 comments we could not find a reason to talk you out of it.
No theme data on this one. Amazon only groups written reviews for some listings and this is not one of them, which leaves 243 ratings averaging 4.3 and not much else to go on.
That is a thin sample by the standards of this list, and a thin sample moves fast — a good early average can slide once a few thousand more people have used the thing.
WinnerReviews places it at #10 on rating and review volume alone, because there is no theme data to weigh.
