At Pure Filters, transparency does not stop at our products. It extends to the data. Here are the complete test results from Envirotek Laboratories (USA) on our Coldstream FTO+ filters.
How to read a filtration test
An analysis table can quickly seem technical. Here are the three key points to understand before interpreting the figures:
- Results are measured across the filter's entire lifespan, not just at the start.
- The reduction percentage varies depending on the contaminant and the volume of water filtered.
- A test run until complete filter exhaustion is more reliable than a partial test conducted under ideal conditions.
Why fluoride and nitrates are special cases
Unlike chlorine, bacteria or pesticides, ions such as fluoride and nitrates are extremely soluble. They require specific filter media based on ion exchange resin, which the ceramic + activated carbon technology of the FTO+ does not primarily target.
This is a fact we prefer to explain rather than hide.
What the results show: evolving performance
| Contaminant | Start (0–500 L) |
Lowest point (2 000 L) |
At 3 000 L |
|---|---|---|---|
| Fluoride | ~90 % | ~4.55 % | ~17.05 % |
| Nitrates | >60 % | ~29.63 % | ~59.6 % |
| Heavy metals | Effective | Varies by metal | Variable |
| Chlorine, VOC, HAA | >95 % | >95 % | >95 % |
| Pesticides, pharmaceutical residues | Very high | Stable | Stable |
| Viruses, bacteria, cysts | >99.99 % | >99.99 % | Maintained at 3 000 L |
Source: Envirotek Laboratories · ISO 17025 accredited. View all our laboratory tests.
Why these values are not linear
The fluoride and nitrate curve may surprise you: performance drops around 2 000 L, then recovers at 3 000 L. This is not a measurement error. At around 2 000 L, the filter's adsorption sites are partially saturated and temporarily release some of the captured ions. This is the lowest point of the curve. Past this stage, the filter reaches a new equilibrium and performance recovers. That is why we show three columns rather than a single "end of life" value: the point at 2 000 L is the lowest, not the representative point for the filter's lifespan.
Key takeaways
- The 3 000 L capacity mainly concerns microbiological filtration (viruses, bacteria, cysts) where the filter remains exceptional.
- For lasting protection against fluoride and nitrates: replacement every 6 months or 1 500 litres, whichever comes first.
Our commitment: giving you high-performing filters and the data to understand how to use them best.
In summary
For the vast majority of contaminants found in Swiss tap water, Coldstream technology provides lasting and reliable protection. Highly soluble contaminants like fluoride and nitrates require more frequent replacement to maintain high reduction rates.
This is a reality we acknowledge and communicate clearly, unlike other brands that only publish partial tests conducted under ideal conditions.
To go further, watch the independent analysis by Les nouvelles anciennes, which compares several water purifier brands, or consult directly our complete laboratory results.
Sources: Envirotek Laboratories LLC (USA) · ISO 17025 accredited · Complete tests available here