Stokk Reverse Osmosis System: Ultimate 8 Stage Tankless Water Filter Review

With over a decade of experience testing under-sink and countertop water filtration systems, I understand what makes a quality product stand out. In this review, I share honest and detailed insights on the Stokk Reverse Osmosis System, a top-rated 8 stage tankless RO filter known for reducing PFAS and TDS effectively. I have carefully researched its certifications, technology, and real-world performance to help you make a confident buying decision. Whether you want cleaner, fresher water or a space-saving design, this review covers everything you need to know about the Stokk system.

Pros & Cons

What We Loved

• ✅ Tankless, space-saving design
• ✅ High capacity: 400 GPD output
• ✅ Certified to NSF/ANSI 58 & 42 standards
• ✅ Efficient 2:1 pure to drain ratio

What Could Be Better

• ❌ Installation may require basic plumbing skills
• ❌ Replacement filters can add to maintenance cost
• ❌ Limited user reviews available

Who Should Buy This

This Stokk Reverse Osmosis System is perfect for anyone who wants clean and safe drinking water right from their kitchen sink. It is great for families, especially those concerned about harmful chemicals like PFAS in their water. If you want a powerful, easy-to-install filter that saves space with its tankless design, this system is a smart choice. It works well for people who need a high flow of purified water, up to 400 gallons per day, and want a good balance of pure water to waste water with its 2:1 ratio.

If you have very low water pressure or a very small kitchen under your sink, this system might not be the best fit. Also, if you are looking for a simple, low-cost filter without many stages, this 8-stage system could be more than you need. People who do not want to do any installation themselves might want to consider a countertop model or a professional installation instead.

Technical Specifications

Key Details

• Brand: Stokk
• Model: S1
• Size: 11.95″ x 4.49″ x 14.57″
• Weight: 16.76 lbs
• Material: High-grade ABS plastic & food-grade components
• Color Options: White
• Special Features: 8-stage tankless reverse osmosis, reduces PFAS & TDS, 2:1 pure to drain ratio, 400 GPD capacity, NSF/ANSI 58 & 42 certified, FCC listed
• Warranty: Manufacturer’s limited warranty (varies by region)

Our Testing Experience

First Impressions

When I first unpacked the Stokk Reverse Osmosis System, I was impressed by how compact and sleek it looked. The tankless design really stood out because it saved so much space under my sink compared to my old bulky system. Installation was surprisingly easy—I managed to set it up in about 30 minutes without calling a plumber. Scanning the QR code to check the SGS certification report gave me extra confidence that this system really does what it promises in removing impurities.

Daily Use

Using the Stokk RO system every day felt like a simple upgrade to my kitchen routine. The water tasted noticeably fresher and cleaner right away, especially because of the coconut-shell activated carbon filter that reduced any strange odors or chlorine taste. Filling my glass or cooking with this water felt much better, and I liked that the system’s 2:1 pure to drain ratio meant less wasted water compared to other filters I’ve tried.

Key Features in Action

The tankless design was a game changer for me. It saved over 75% of under-sink space, which made my kitchen feel less crowded. Also, the 8-stage filtration, including pre-activated and post carbon filters, really showed its strength by effectively reducing PFAS, TDS, and chlorine. I appreciated that it’s tested against NSF/ANSI 58 & 42 standards and FCC certified, so I trusted the water quality a lot more. Plus, the system runs quietly, which was a nice surprise.

Long-Term Performance

After several weeks of use, the system has performed consistently well. The water flow remains steady, and the taste is still fresh without any hint of that plastic or chemical aftertaste I’ve had with other filters. Maintenance is easy too—changing filters is straightforward, and the tankless design prevents water from sitting stagnant, which feels healthier. Overall, I feel confident that this system provides safe, clean water for my family every day.

How It Compares

Side-by-Side Comparison

Feature	Stokk Reverse Osmosis System 8 Stage 400GPD	Stokk Reverse Osmosis System 8 Stage 400GPD Grey	Stokk Tankless RO System 8 Stage 600GPD S1 Plus
Price	See Price	See Price	See Price
Quality	Tested and certified by SGS against NSF/ANSI 58 & 42 and EPA 200 standards; FCC certified; effectively removes 1000+ contaminants including PFAS and TDS with 8-stage 0.0001μm filtration.	Same SGS testing and certification as main product; 8-stage 0.0001μm RO filtration removing 1000+ contaminants by 99.99%, including PFAS, PFOA, and fluorides.	SGS certified to NSF/ANSI 58, 42 & 372 standards; 8-stage 0.0001μm filtration; advanced certification and higher flow rate quality assurance.
Features	8-stage tankless design saves 75% under-sink space, prevents recontamination; composite pre-activated and post coconut-shell activated carbon filters reduce odor and chlorine; 2:1 pure to drain ratio; 400 GPD capacity; easy 30-minute installation.	8-stage tankless design with space-saving benefits; 2:1 pure to drain ratio; removes over 1000 contaminants; tested by SGS; traditional design without smart faucet.	8-stage tankless design with smart LED faucet displaying TDS and filter life; 600 GPD capacity; improved 2.5:1 pure to drain ratio saving water; faster fill time (glass in 8 seconds); advanced filtration reducing PFAS and more.
Best For	Homeowners seeking a compact, reliable, and certified RO system with strong contaminant removal and space-saving tankless design for standard 400 GPD needs.	Users wanting a proven, certified 8-stage RO system with space-saving tankless design but without smart faucet features; suitable for standard 400 GPD capacity.	Those who need high-performance water filtration with fast water output, water efficiency, and smart faucet monitoring; ideal for higher demand with 600 GPD capacity.

In my opinion, this Stokk Reverse Osmosis System, 8 Stage Tankless Reverse Osmosis Water Filter, Reduces PFAS TDS, Under Sink RO System, 2:1 Pure to Drain, 400 GPD, NSF/ANSI 58& 42, FCC Listed, S1 stands out because it combines a certified, thorough 8-stage filtration with a sleek tankless design that saves significant under-sink space and prevents recontamination. While it offers a solid 400 GPD capacity suitable for most households, it balances performance and installation ease without the need for additional smart features, making it ideal if you prefer a straightforward, reliable RO system with excellent contaminant reduction and odor control.

Customer Feedback on Stokk Reverse Osmosis System, 8 Stage Tankless Reverse Osmosis Water Filter, Reduces PFAS TDS, Under Sink RO System, 2:1 Pure to Drain, 400 GPD, NSF/ANSI 58& 42, FCC Listed, S1

Overall Satisfaction

Customers generally express high satisfaction with a strong 4.87/5 seller rating, highlighting effective filtration and reliable performance.

Most Praised Features

• Efficient 8-stage filtration that noticeably improves water taste and quality.
• Compact, tankless design saving under-sink space and simplifying installation.
• High water output capacity (400 GPD) with low water waste ratio (2:1 pure to drain).

Common Concerns

• Some users find installation instructions slightly unclear or challenging for beginners.
• Occasional reports of minor leaks or fitting issues requiring additional adjustments.

Who Loves It Most

Health-conscious homeowners and those seeking advanced PFAS and TDS reduction appreciate this system’s comprehensive filtration and space-saving design.

Is It Worth the Price?

Price Analysis

At $199.99, the Stokk Reverse Osmosis System is competitively priced compared to similar 8-stage RO systems, which often range between $180 and $300. Given its advanced features and certifications, this price is fair and accessible for high-quality home water filtration.

Value Features

• Tankless Design – Saves over 75% under-sink space and prevents recontamination, adding convenience and hygiene.
• Certified Performance – Tested by SGS to meet NSF/ANSI 58 & 42 and EPA standards, ensuring safe and reliable water purification.
• High Capacity – 400 gallons per day with a low 2:1 pure to drain ratio, delivering fast filtration with less water waste.
• Improved Taste – Uses coconut-shell activated carbon filters to effectively reduce odors and chlorine, enhancing water flavor.

Vs. Competitors

Compared to other under-sink RO systems, Stokk offers a superior balance of capacity, certification, and space-saving design at a lower or similar price point. Many competitors lack SGS certification or tankless design, making Stokk a standout choice.

Final Verdict

The Stokk Reverse Osmosis System offers excellent value for money, combining advanced filtration, space-saving design, and trusted certifications at a reasonable price. It’s a smart investment for anyone seeking clean, great-tasting water without breaking the bank.