Pure Filters vs Ultimate Star Filter
In the world of gravity-fed water filters, there are many marketing promises but not all of them are equal.
At Pure Filters, we have always prioritized absolute transparency and independent validation of our performance. Today, true to our approach, we objectively compare the tests of Pure Filters equipped with the Coldstream FTO+ with those of the emerging Ultimate Star Filters.
Our Goal : Enable you to clearly distinguish between enticing claims and truly proven performance, so you can make an informed and responsible choice.
Important note : A lab test is not a certification.
We prefer reports from ISO/IEC 17025 accredited laboratories and following NSF/ANSI protocols (42, 53, 401, P231) for drinking water. Side Example Coldstream FTO+ (CF163W): tests under 42/53/P231 by IAPMO/Envirotek, on 3,000 L, with publication of a detailed performance sheet.
Conversely, SGS Xiamen reports published by Star Filter are labelled "for scientific research and internal quality control only – not for product certification", and are not covered by ISO/IEC 17025 accreditation for the performance of domestic filters. They remain informative, but not certifying.
Update – November 2025: New Star Filter Tests and Deceptive Testing Protocol
Since the initial publication of this article, Star Filter has released new laboratory reports dated 2025, conducted by SGS-CSTC Xiamen Branch, a regional subsidiary of the SGS Group in China. These documents are presented as "endurance tests" conducted on 3,000 to 3,200 liters, indicating reductions of more than 99% for various contaminants (heavy metals, PFAS, bacteria, and coliphagous MS2 virus). The reports specify, however, that they were carried out "for internal research purposes" and "without certification value".
What these tests really reveal:
• All SGS Xiamen reports mentioned are internal tests, not certifying.
• The methods discussed (GB/T 5750, EPA 537.1, EPA 1602) are analytical methods (measurement of concentrations), not filter performance standards such as NSF/ANSI 42, 53, 401 or P231.
Contrary to what is stated on the Star Filter website, the SGS Xiamen reports provided do not establish an ISO/IEC 17025 accreditation applicable to the tests presented; on the contrary, they indicate an "internal research" use and the absence of certification value.
In other words: exploratory tests, non-certifying, in a non-accredited framework.
Star Water Filter: "NASA membrane" or carbon + UF 0.01 μm combo ?
To our knowledge, there is no evidence that Star Filters uses Ahlstrom/Argonide Disruptor media (sometimes referred to as "NASA technology").
Ahlstrom's technical documents describe an electro-adsorbent nonwoven, not a 0.001 μm membrane. The characteristics announced by Star Filters and the industrial indices observed correspond rather to OEM cartridges of the carbon block + UF 0.01 μm membrane type.
What the technical sources say :
• Ahlstrom/Argonide Disruptor is a nano-alumina-based electro-adsorbent nonwoven media; The retention of submicron particles is done by charge, with an average size of physical pores around 1.25 μm — we are not at all on a "0.001 μm membrane".
• The "NASA" storytelling refers to historical SBIR funding of Argonide, which was then taken over under an exclusive license by Ahlstrom (Disruptor). Again, there is no indication that Star Filter has a license on this medium.
Concrete clues (visuals and market) :
• The cross-section photo provided by SWF shows a dark block (agglomerated carbon) with a pleated central element type UF, the classic signature of OEM "carbon + UF 0.01 μm" cartridges.
• The sheets and reports that SWF highlights align with Chinese OEM grammar (carbon + UF 0.01 μm block, "tested by SGS Xiamen", volumes 3,000–3,200 L, flow drops at end of life).
Interim conclusion :
• Probable carbon + UF 0.01 μm combo. No public evidence of a media Disruptor "NASA technology" used by Star Filter. If SWF publishes a media ID, an Ahlstrom/Argonide license, or NSF/ANSI-type certifying reports, we will update.
Contradictions noted on the SWF website (end of November 2025) (examples noted by us) :
• Product sheet: "nanofiltration membrane up to 0.001 μm", PF-2 compatibility, flow rate 12 L/h and 6,000 L per pair, "retains minerals".
• FAQ/Blog: Recurring claim of a "NASA-developed membrane", 0.001 μm, presence of silver (in the coal and/or membrane).
• On the subject of the NSF: on the one hand, "all the components are NSF certified; the filter is in the process of being certified"; another "the only NSF-certified activated carbon-based gravity filter".
Why is it stuck ?
• "0.001 μm" is a typical claim of pressure nanofiltration/RO. In gravity, without a pump, a true NF 0.001 μm would have a flow rate of almost zero — the opposite of the announced flow rates.
• The Disruptor technology (if it were it) is not a "0.001 μm membrane" but a non-woven electro-adsorbent media; to speak of "NASA membrane 0.001 μm" maintains confusion.
• On the NSF side, a product is never "NSF certified" en bloc: each model is certified, if it is, for specific claims (materials, chlorine, lead, P231, etc.). Generic or contradictory formulations must be clarified by the trademark.
A biased comparison with Coldstream
Star Filter also published an SGS Xiamen test on a Coldstream FTO Plus (CF163W) filter, concluding that it "does not effectively filter viruses".
However, this test was not commissioned by Coldstream and its protocol is questionable:
• Total volume: 100 L only.
• Influent viral concentration: 4.2×10⁵ PFU/mL. For reference, theU.S. EPA (1987), the basis of NSF/ANSI P231, prescribes a challenge of 10⁷ PFU/L, or 1×10⁴ PFU/mL. The SGS test applied to the CF163W therefore used a load ~42× higher than this benchmark, and ~17× higher than the load used in the KLT/Coldstream rotavirus tests (2.4642×10⁷ PFU/L), which shows > 99.99% reduction up to 3,000 L.
• The "EPA Method 1602" cited is a method for counting coliphages; It does not set an influent concentration to evaluate the performance of a purifier.
• 4.2×10⁵ PFU/mL (i.e. 4.2×10⁸ PFU/L) exceeds the high range frequently reported for raw wastewater (10⁶ PFU/L), which makes the comparison with domestic use of little interest.
Meanwhile, the tests carried out on the Star Filters themselves (SGS 2025) have been conducted under much more favourable conditions (volumes 3,000–3,200 L, "reasonable" loads), and remain unaudited internal tests. Two protocols, two realities: realistic and advantageous for their products; extreme and unrealistic for Coldstream.
What to remember
The difference is not due to a simple difference in method: it reflects a double standard. The same players choose "reasonable" measurement conditions for their own filters, but extreme conditions for a competitor. Conversely, Coldstream tests performed by Envirotek/IAPMO (ISO/IEC 17025 accredited laboratories) meet NSF/ANSI P231 protocols and show a 99.99% viral reduction > 3,000 L, under prescriptive and verified conditions.
Correction of fluoride and nitrate claims
Star Filter claims that Coldstream FTO+ filters "do not filter fluorine or nitrates." This presentation is incomplete.
Fluorides: real reduction but strongly dependent on volume and load
• Fluorides (F⁻) are anions that are difficult to capture. The Coldstream tests (CF163W) show a high reduction at the beginning (≈ 97.5% in the first liters), still ~ 90% around 500 L, then a marked drop to ~ 17% at 3,000 L, with a "challenge" water dosed at 8.8 mg/L F⁻. In typical real water (0.1–0.5 mg/L), saturation occurs later and performance is maintained for longer.
Nitrates: measured and sustainable reduction (without dedicated resin claims)
• Contrary to the "no reduction" claim, Coldstream data for CF163W show a reduction in nitrate (NO₃⁻) of approximately 66% at 500 L and ~60% at 3,000 L for water spiked at 29.7 mg/L NO₃⁻. Coldstream does not claim the use of ion exchange resins specific to nitrates in its consumer sheet; The reduction observed is nevertheless measured in the laboratory and published.
Understanding Coldstream FTO+ Filtration Results
In summary, Coldstream FTO+ filters (*) are not aimed at "distilled water", but at purified and balanced water: priority is given to microbiological safety (P231) and the documented reduction of a wide spectrum of contaminants (NSF/ANSI 42, 53), while maintaining a natural minerality. The referenced tests are conducted under NSF/ANSI standards 42, 53 and P231 by an accredited laboratory (Envirotek/IAPMO).
Technology: Star Filter vs Coldstream
Star Filter :
• Most likely architecture: sintered activated carbon block + integrated 0.01 μm UF membrane (polymer), typical of Chinese OEMs; operation by adsorption + UF sieving; Progressive clogging that cannot be "recovered" by brushing.
Coldstream FTO+ (CF163W) :
• Brushable ceramic shell + internal activated carbon; external microbio barrier, internal adsorption for chemicals; Regular cleaning possible, more stable flow over time.
Star Filter :
- SGS Xiamen 3,000–3,200 L report series (metals, PFAS, bacteria, MS2, etc.). Useful but explicitly non-certifying reports ("for research/internal QC only").
Coldstream FTO+ :
- Testing and certification via IAPMO/Envirotek, under NSF/ANSI 42/53/401/P231/600 standards, with publication of 3,000 L performance sheets.
- P231 (microbiology): 6 log bacteria and > 4 log viruses tested up to 3,000 L, as part of the purifier protocol.
- 42/53/401 (chemicals): high reduction over a wide range (VOCs, SVOCs, HAA5, pharmaceuticals), always measured at 3,000 L; see the CF163W data sheet.
PFAS: what evidence can be relied on ?
For PFAS, we rely primarily on the historical ProOne trials conducted by Envirotek (ISO/IEC 17025) including P-473 (PFOA/PFOS), at the time when ProOne marketed the cartridge manufactured by KLT Filtration (*) (Coldstream). These reports, even if they are in the name ProOne, describe the performance of media identical to that subsequently used by Coldstream FTO+ on that time segment.
In practice: ProOne results cover PFAS, 42/53/401 and P231 (50 gallons on P231 in this protocol), and serve as an independent anchor to PFAS where published Coldstream FTO+ sheets do not always display the PFAS line in plain text.
Critical reading of SWF's published SGS reports :
• Reports often advertise "> 99%" on contaminant batteries up to 3,000–3,200 L, but with a single sample and analytical methods (GB/T, EPA 1602, 537.1) outside of the certification protocol.
• The mention "for scientific research and internal quality control only – Not for product certification" limits the use of these documents in direct comparison with NSF/IAPMO certificates.
• Example virology (MS2) and bacteria (Salmonella): high reductions announced, but "standard disinfection" protocol and imposed flow rate (0.15 L/min) — this is not a standardized gravity protocol of the P231 type.
Our position at the end of November 2025
• On the technology: in view of the Ahlstrom/Argonide technical documents and the industrial indices (visuals, flow rates, test volumes, OEM grammar), Star Filter is most likely based on a "carbon block + UF 0.01 μm" design and not a "0.001 μm membrane" NASA/Disruptor.
• On evidence: SGS Xiamen reports are useful but not certifying; we favor accredited and normative tests to compare commercial claims, which is published by Coldstream (IAPMO/Envirotek) and, for the historical PFAS, ProOne.
Clear conclusion for the reader : If you want a gravity filter with strong prescriptive evidence over time (3,000 L tested) and readable technology, Coldstream FTO+ ticks the most boxes today, with IAPMO/Envirotek reports and an exhaustive scorecard.
On the Star Filter side, the positioning is mainly based on "membrane/NASA/0.001 μm" communication and internal SGS reports. This does not prove inefficiency, but it is not at the same level of demonstration or traceability. We will remain open to any future release of media licenses, patent numbers, NSF/IAPMO certificates, and comprehensive high-volume reports.
For more information: Lab Testing – Coldstream Water Purifier
Methodology and standards used
Pure Filters equipped with the Coldstream FTO+ :
- Independent laboratory: Envirotek Laboratories (USA), EPA and IAPMO accredited.
- Standards applied: NSF/ANSI Standard 42, 53, P-231, and 401.
- Tested volume: up to 3000 liters, with readings every 500 liters.
- Scientific rigor: details provided for each substance tested, by volume band.
FTO +Haloacetic Acids Reduction Testing: Passed
Gravity Filters FTO+ TEST REPORT
Star Water Filter equipped with Ultimate Star Filter :
– Wessling France (ISO 17025 accredited): triplet chemical tests on doped demineralized water, unit volume 10 L, flow rate 150–250 ml/min.
– SGS Xiamen (China): microbiological tests and some spot tests on 10 L; ISO 17025 accreditation is not indicated in the documents we have received. Variant if you validate the proof of lack of accreditation: "non-ISO 17025 accredited laboratory".
– Remember: the chemical tests published are on initial volumes (10 L). They do not document the stability of the results over the claimed lifetime.
SGS STARFILTER Laboratory Test
Review of WESSLING FRANCE STARFILTER via the website https://starwaterfilter.com/fr/content/10-resultats-d-analyses-du-filtre-ultimate-star-filter
SGS STARFILTER BACTERIA Laboratory Test
SGS STARFILTER VIRUS Laboratory Test
SGS STARFILTER SALMONELLA Laboratory Test
The tests come from the official Starfilters website https://starwaterfilter com/faq
To date, the chemical tests published by Star Water Filter have involved unique volumes of 10 L of spiked water; They do not document the stability of the results over the lifetime." Technical justification: the Wessling v2 report describes tests on doped demineralized water, in triplicate, and specifies that the synthesis includes the best of the three results; This document does not include chemical resistance tests on cumulative volumes.
Series of contaminants tested and significant results
Pure Filters equipped with Coldstream FTO+ :
• Very broad spectrum: volatiles, metals, pesticides, pharmaceuticals, herbicides, microorganisms, inorganic compounds.
• Very wide spectrum covered, with step-by-step readings up to 3000 L according to the laboratory documentation provided by the manufacturer. It is this type of tiered protocol that makes it possible to attest to performance over time.
Star Water Filter equipped with Ultimate Star Filter :
• Tests on PFAS, drugs, plasticizers, solvents, hormones, heavy metals.
• Wessling v2 publishes high laboratory abatements (PFAS, plasticizers, disinfectants, solvents/HVOC, drugs, hormones, metals), presented as the best result among three parallel trials on 10 L doped. Some values are more modest depending on the case (e.g. p,p'-DDE; selenium at pH 6.5; barium at pH 8.5).
Seriousness and credibility of the tests
Both brands publish trials aligned with known standards (NSF/EPA for Coldstream; NSF/ANSI referenced in the Wessling protocol for Star). The difference is mainly due to accreditation and temporal depth:
– Coldstream FTO+ : multi-stage tests up to 3000 L.
– Star Water Filter : chemistry tested by Wessling, ISO 17025 accredited laboratory; part of the tests were also carried out by SGS Xiamen, without mentioning ISO 17025 on the documents provided.
As a result, robustness "over time" is demonstrated at Coldstream FTO+, while the excellent Star Wtaer Filter abatements published at 10 L do not prejudge the resistance at 1500–3000 L.
Why the identity of the filter under test is essential A: We do not doubt the authenticity of the SGS reports received. The membrane announced by Star WF is internal, it is normal that it is not visible on the external photos. On the other hand, Star WF does not publish an actual cutaway photo of the media; only a model is proposed. Given the superior performance of a conventional activated carbon block across multiple families, we would like more visual transparency on the exact composition, just to build trust.
Synthetic comparison
Comparing Performance on Viruses: What the Tests Really Say
The MS2 virus test, used to certify the Starfilters filter, is a standardized and valid approach based on a non-pathogenic virus. Coldstream has tested its filters on a real virus, rotavirus, providing direct evidence of the elimination of a pathogenic virus. This reflects a more committed approach, but also more scientifically demanding.
Virological tests are often difficult to compare because laboratories use different models. Here is a summary table to better understand the difference between the test used by Starfilters (MS2 Coliphage) and the one used by Coldstream (Rotavirus).
Comparing performance on bacteria: what the tests really say
Microbiological performance is critical for any gravity filtration system. But to interpret them correctly, it is also necessary to examine the methodology used.
The table below compares the results obtained on bacteria from the Coldstream FTO+ filters (Pure Filters) and Ultimate Star Filter (Starfilters), based on their respective laboratory reports.
Coldstream tests were carried out by Envirotek Laboratories (USA), according to EPA and NSF standards, with a documented efficiency up to 3000 liters.
The Starfilters tests were conducted by SGS, following Chinese health standards (Ministry of Health, GB/T standards). They show a high initial efficiency (>99.9999%), but a visible drop mid-cycle, especially at 2250 L.
This comparison is not intended to disqualify one method in favor of another, but to allow everyone to understand what was actually measured, and under what conditions.
This is shown on pages 6 to 14 of the Eurofins report :
Subject: REACH control of 247 SVHC substances in homogeneous cartridge materials (T1: PP cover + silicone gasket + EVA glue; T2: non-woven; T3: activated carbon rod). In-house analytical methods (GC-MS, LC-MS, ICP-OES, UV/VIS, CI), detection limit 0.010% w/w. Result: not detected for all SVHCs tested on T1/T2/T3, therefore "PASS" with regard to the REACH threshold 0.1%. These tables list the ECHA candidate list; They do not measure filtered water or a reduction in pollutants.
Conclusion
The Wessling v2 tests published by Star Water Filter describe a high initial performance on doped water, in triplicate, with the best result presented for each family. This is useful for characterizing a potential for abatement, but it does not demonstrate chemical resistance over hundreds or thousands of liters. FTO+ documents, on the other hand, are based on protocols with step-by-step tracking up to 3000 L, which makes it possible to assess stability over time.
For its part, Star Water Filter shows very promising performance, particularly on the microbiological part, but only on the initial phase or without clear demonstration of stability over time for chemical contaminants and heavy metals.
To date, on the chemistry side, the tests published by Star Water Filter have focused on single volumes of 10 L of spiked water; Cumulative volume chemical endurance data would be required to document the stability of the results.
Eurofins documents confirm material compliance with SVHC REACH (PASS <0,1 % sur T1/T2/T3). C’est positif pour l’innocuité des composants, mais distinct d’un test de performance de filtration de l’eau
Finally, since the Ultimate Star Water Filter filters are partly made of activated carbon, it is realistic to recommend, as with any filter of this nature – including the Coldstream FTO+ – a replacement every 6 to 8 months.
The difference is that Pure Filters clearly indicates this, consistent with laboratory results, while Ultimate Star Filters do not specify a realistic limit in their communication, and no test demonstrates stable effectiveness over time.
••• The tests in doped demineralized water (Wessling) isolate the media and produce very reproducible initial abatements thanks to the triplicate and the presentation of the best of the three results — a positive point — but they do not reflect either the complexity of real water or endurance over cumulative volumes — a negative point; conversely, the step-by-step method up to 3000 L (Coldstream/Envirotek) documents the stability of performance over wear — a positive point — at the cost of longer and more expensive tests — a negative point.
•• It is important to remember that these filters are based on activated carbon, a material whose effectiveness decreases over time. An honest and objective recommendation would be to replace them every 6 to 8 months maximum, which corresponds to the technical reality and market standards.
• In addition, at the time of writing, the pair of Ultimate Star Filters is displayed at €150. Each will assess the value/price ratio against comparable technologies and published evidence.
Are you hesitating between several brands of filters? Don't miss the full analysis of "The Old News": Gravity filters: which one makes water REALLY healthy ?
Official Star Water Filter sources:
– Wessling France, Laboratory expertise report – Ultimate Star Filter, report ULY-025013, version 2 of 14/08/2025: doped demineralized water, triplicate, presentation of the best result; flow rate 150–250 ml/min (10 L bowl); Reference to the raw results appendix ULY25-025013-2.
– Eurofins Testing Technology (Shenzhen), EFSN25040473-C-0101, 21/04/2025: REACH inspection of the 247 SVHCs on T1/T2/T3 materials, LOD 0.010%, PASS result < 0.1%
https://starwaterfilter.com/fr/content/10-resultats-d-analyses-du-filtre-ultimate-star-filter
Article "Ultimate Star Filter vs Pure Filters" (statements "NF 0.001 μm", "NSF soon") and "Performance"/product sheet page (NASA/0.001 μm claims)