I Tested The Best Reverse Osmosis Counter Top Water Filters (So You Don’t Have To)

In this article, I test three of the most popular countertop reverse osmosis water filters: the AquaTru Carafe , RKIN U1 and Waterdrop A2, to see which countertop reverse osmosis water filter actually delivers the cleanest water and has the best overall experience. Let's dive in.

Why Water Filtration Matters?

With water being a fundamental need, I've always been conscious of the quality of water I'm drinking and what I'm putting into my body.

As someone with a compromised immune system, I've been advised against under-the-counter water filtration units due to the mold, bacteria, and contaminants that can grow in dark and damp places and instead I prefer to use countertop water filters.

Most tap water today (in the US) contains trace amounts of:

• PFAS (forever chemicals)
• Heavy metals (lead, arsenic)
• Microplastics
• Chlorine and chloramine
• And even pharmaceutical residues

Check out EWG to see what the water is like in your area. So choosing the right filtration system isn’t just about taste, it’s about lowering your toxic load and supporting your health.

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Understanding Reverse Osmosis

Reserve Osmosis (RO) is a water purification process that removes ions, molecules, and other particles from water by applying pressure to push it through a semipermeable membrane. The membrane allows water to pass while blocking contaminants such as salts, minerals, bacteria, and other impurities.

Only some of the water passes through (the purified portion). The rest, which carries the concentrated contaminants, is flushed down the drain to prevent membrane clogging.

Most under-sink or older countertop RO systems have a waste-to-pure ratio of: 3:1 → 3 gallons wasted for every 1 gallon purified. Additionally, although reserve-osmosis water filters are great at removing the contaminants from water, they also, unfortunately, remove the minerals too. To maintain water quality, it is therefore crucial to re-mineralize the water and add minerals back.

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Understanding TDS

TDS stands for Total Dissolved Solids, which measures the amount of dissolved particles in water.

Typical ranges look like this:

• Distilled / RO Water = Very low
• Spring / Mineral Water = Moderate
• Tap Water (EPA limit) = Up to 500 ppm

Low TDS isn’t automatically better, as it just means fewer dissolved solids.

If TDS is high because of natural minerals, that’s often a good thing, but if it’s high due to contaminants, that’s when filtration becomes important.

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Size and Aesthetics

Size and aesthetics are important as you want something that can fit nicely into your kitchen and can also be used and manoeuvred easily.

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AquaTru Carafe

The AquaTru is the smallest and most countertop-friendly option of the three. It has a clean white design and includes a glass carafe, which helps reduce plastic exposure. I think it's definitely prettier than the AquaTru Classic, but the smaller pitcher is inconvenient when changing the water.

• Dimensions: 14” x 7.5” x 17”
• Weight: 9 lbs
• Water Tank: 0.7 gallons (2.5 L) - 0.5 gallons of filtered water and 0.2 gallons of reject‍
• Filtration speed: Purifies 0.5 gallons in 10-15 minutes
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RKIN U1

• Dimensions: 19” x 9.5” x 17”
• Weight: 24 lbs‍
• Filtration speed: Purifies 0.5 gallons in 7-10 minutes
• ‍Water Capacity: 1 gallon total (0.5 gallons of filtered water and 0.5 gallons of reject)

The RKIN is significantly larger and heavier than the others. It has a sleek black design and looks more like a high-end kitchen appliance than a traditional water filter.
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Waterdrop A2

• Dimensions: 15.9” x 8.2” x 15.7”
• Weight: 22 lbs
• ‍Filtration speed: Unknown‍
• Water Tanks Capacity: 1.25 gallons (4.7L)
• Pure Water Tank Capacity: 0.3 gallons (1.1L)

The Waterdrop sits in the middle in terms of size and design. It has a modern grey finish and a touchscreen interface, but a very small clean water capacity so will need to be continuously refilled.
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🥇 RKIN U1 – Most premium appliance design
🥈 AquaTru Carafe – Compact but sleek design
🥉 Waterdrop A2 – Modern touchscreen aesthetic but smaller tank

Size & Design Winner: RKIN U1

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Filtration Technology & Features

AquaTru Carafe

Uses 4-stage Ultra Reverse Osmosis filtration:

• Pre / Carbon filter
• Reverse Osmosis membrane
• VOC carbon filter

It’s tested to NSF standards and removes up to 99% of contaminants, including heavy metals and chemicals. The AquaTru doesn't have all the bells and whistles like other products. It's simple and focuses on filtering water to a very high standard, which I like.

The carafe is made from strong, durable borosilicate glass and designed for easy pouring. Has a compact design that fits easily in your fridge if you'd like cold water. The pre-filtered/unfiltered tank is made out of Tritan® plastic (a BPA-/BPS-free plastic). For an extra $20 you can get a filter with an optional alkaline mineral boost, to help remineralize your water. It also has a 2.7 pure water : 1 waste water ratio so is very efficient (63%)

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RKIN U1

Also has a 4-stage filtration system:

• Sediment filter
• Carbon filter
• RO membrane
• Alkaline post filter
• Optional hydrogen infusion

The RKIN U1 is easily the most advanced all-in-one countertop water filter out of the three systems. It not only uses reverse osmosis to purify your water, but it also gives you the ability to dispense water at different temperatures, ranging from 59°F all the way up to 212°F, making it convenient for things like coffee, tea, or even warming milk.

The system also includes a smart display that provides real-time information such as when the water is being filtered, when the tank needs to be refilled, water temperature, hydrogen content (PPB), and TDS (Total Dissolved Solids). It will also notify you if something goes wrong. Filter indicator lights make maintenance easy, turning yellow when the filter reaches 80% of its lifespan and red when it’s time to replace it.

Another standout feature is the self-cleaning function, which uses UV sterilization and rinse cycles to help keep the system clean and reduce manual maintenance. From an efficiency standpoint, the RKIN has a 1:1 pure-to-waste water ratio, meaning for every gallon of purified water produced, one gallon is discarded (50%).

That said, there are a few drawbacks. The large rear reservoir can be quite heavy when full, making refilling a bit inconvenient. Additionally, the water containers are made from plastic and currently lack third-party material safety certifications, which may be a consideration for people trying to minimize plastic exposure.

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Waterdrop A2

Uses 5-stage filtration:

• PP sediment filter
• Carbon block
• RO membrane (0.0001 micron)
• Taste-enhancing layer
• UV sterilization

The Waterdrop A2 is strong on paper but has less independent testing available. Unlike the AquaTru, it also has temperature options. This one has preset temperatures, and you can choose from 59, 77, 113, 149, 185, and 203. It was a pure to drain ratio of 3:1, which is the best out of the three (75%) and is capable of providing 100 gallons of purified water per day.

Waterdrop claims to be NSF certified for the international ANSI and NSF 372 standard for lead-free material, but this isn't publicly displayed on their website. Some downsides are the material of the tank and the holding container is plastic, and the tank will need to be replaced atleast 1-2x per day.

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🥇 AquaTru – Strongest third-party testing and certification
🥈 Waterdrop A2 – 5-stage filtration + UV sterilization
🥉 RKIN U1 – Feature-rich but less verified

Filtration Winner: AquaTru

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Ease of Setup

AquaTru

Easiest setup of all three.

Steps:

1. Unbox and plug in the filters.
2. Plug it into the wall.
3. Fill the tank
4. Run a few flush cycles

Good to go.

RKIN U1

Like the AquaTru, the set up for the RKIN U1 is very straightforward. The flush cycle takes about 6 minutes per rinse and needs to run several times. Press and hold the rinse button for 3 seconds. More water needs to be replaced and it takes longer, so it's less convenient but a simple process.

Waterdrop A2

The set up for the waterdrop is supposed to be simple like the others but I found the instructions quite complicated. It follows a similar idea to the others as you install the filters and run multiple flush cycles but it kept getting stuck at 50% youy have to press a button once it starts flashing and replace it again. It took me a while to get my head around it and it took me atleast an hour to finish setting it up.

🥇 AquaTru – Easiest setup
🥈 RKIN U1 – Still simple
🥉 Waterdrop A2 – More complicated

Ease of Use Winner: AquaTru

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Maintenance and Filter Replacement

AquaTru

3 filters:

• Pre/carbon filter – 6 months ($25)
• RO membrane – 2 years ($52)
• VOC filter – 1 year ($35)

Estimated cost: ~$111 per year

As far as maintenance goes, the pitcher and filter tank need to be cleaned at least once a week with preferably some non-toxic organic soap.
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RKIN U1

The sediment and carbon pre-filter ($39.86), alkaline post filter ($40.43) and hydrogen infusion ($49.70) are recommended to be replaced every 6-12 months, while the reverse osmosis (RO) membrane is recommended for replacement every 12-24 months, depending on local water quality ($78). This averages out at around $225 per year to get clean, filtered water with some hydrogen.

As far as the maintenance goes, however, it does have that self-cleaning with the UV and the rinse feature. So, the only thing that you really need to do is just give the water tank a nice wash about once a week.

Waterdrop A2

The waterdrop has a single filter system with a 12-month lifespan and a low replacement cost of only $69 per year.

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🥇 Waterdrop A2 – Simplest maintenance
🥈 AquaTru – Reasonable cost
🥉 RKIN U1 – Most expensive filters

Maintenance Winner: Waterdrop A2

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Price & Warranty

AquaTru

• AquaTru cost $395 + free shipping. 
• Alkaline Mineral Boost option (+$20) 
• 1 year warranty (can extend to 3 years for $50)
• AquaTru offers a comprehensive 30-Day Money Back Guarantee
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RKIN U1

• RKIN is expensive and cost $1125 (or $700-800 on sale) 
• 1 year warranty (can extend an additional year for +$60)
• Offers a 30 day return window
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Waterdrop A2

• The A2 is a more premium model and costs $499 or ($409 on sale) 
• 1 year warranty (can extend an additional year for +$60)
• Offer a 30 day return window

The waterdrop has a single filter system with a 12-month lifespan and a low replacement cost of only $69 per year.

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🥇 AquaTru – Most affordable
🥈 Waterdrop A2 – Good balance of price and performance
🥉 RKIN U1 – Premium price

Price Winner: AquaTru

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Taste Test

One of the most surprising results of testing was the taste difference between the filters.

RO water should taste neutral, since most minerals and contaminants are removed.

In blind taste testing:

• AquaTru tasted the cleanest and had no flavor
• Waterdrop had a slight residual taste
• RKIN had a noticeable artificial flavor

This may be due to the hydrogen in the RKIN or waterdrops 'taste-enhancing layer' but they tasted plasticy to me and I wasn't a fan.

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Final Verdict: Which Countertop RO Filter Wins?

Although the RKIN and Waterdrop have great additional features, the Aqua Tru is the clear winner for me. The glass carafe is a really nice unit that fits onto a countertop well and looks beautiful. It has a strong 2.7 pure water: 1 waste water ratio and is third-party tested by independent studies to prove how well it filters the water.

At $395 the price is very affordable compared to other RO options and is a clear investment in your health that won't break the bank account. It's easy to set up, use and refill and the filter can be kept and stored in the fridge. The only problems I have are the remineralization aspect you have to pay extra for and the size of the smaller pitcher.

I do really love this product though and would feel confident recommending it to anyone looking for a countertop resverse osmosis water filter. If you're interested in buying your own Aqua Tru, click the link here and use code 'wellnessdaddy' for 10% off.

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For a more in-depth review of my experiences watch the video here.