What does a Stefani filter remove and what does it not remove?

Transparency, Data and Scientific Evidence

This page summarizes test results and available certifications for Stéfani gravity filters. Each claim includes a direct link to the supporting PDF report, because when it comes to health, we must be extremely rigorous.

How to read this information

✅ Remove
= reduction to levels undetectable in the laboratory.

🟡 Reduce = high reduction, depends on conditions (water, concentration, shelf life)

⛔ Not Suitable = beyond the reasonable reach of a domestic gravity system

Summary of results (with evidence)

Each item includes a link to the PDF reports at the bottom of the page.

Bacteriological elimination (E. coli)

Stefani ceramic filters equipped with a sterilizing candle/cartridge have demonstrated a minimum bacteriological reduction of 2 log (99%) of Escherichia coli in laboratory tests, according to the ABNT/NBR 16098 methodology.

In other available bacteriological assays, a reduction in bacterial load is observed to levels that are not detectable under controlled laboratory conditions.

View evidence (2025 Report) View evidence (Costa Rica) View evidence (Brazil 2011) Technical information – Sterilizing Cartridge · Bacteriological assays

Chlorine reduction (taste and odor)

The 2025 report indicates a significant reduction in free chlorine (according to INMETRO classification, a minimum reduction above 75% – Class I) throughout the filter's lifespan, reaching up to 96% under test conditions , according to the ABNT/NBR 16098 methodology.

This reduction results in a clear improvement in the taste and smell of the water.

See evidence (2025 Report) See evidence (INMETRO / classes)
View evidence (Australia) View evidence (USA)

Particle and Microplastic Retention

Tests carried out by accredited laboratories show an average retention efficiency of 86% for particles with a size ≥ 0.5 µm and < 1 µm (Class A classification).

A significant portion of the microplastics detected in drinking water are in the micrometer range. For this reason, the use of Stéfani ceramic filters helps to reduce microplastics within this size range .

This statement is based on particle retention by size and does not constitute a direct measurement of microplastics in the test .

See evidence (2025 Report) See evidence (Candle technical data sheet)

Removable parts / material safety

The 2025 report details the results for extractables within the limits specified in the standard. The technical documentation includes a table of maximum concentration limits.

See evidence (2025 Report) See evidence (Table of limits)

Metals, pesticides and organic compounds (historical trials)

Historical international studies have reported reductions in certain metals, pesticides, and organic compounds under laboratory conditions. Performance may vary depending on the actual water and contaminant load.

View evidence (Australia) View evidence (United Kingdom) View evidence (USA)

pH (does not demineralize like osmosis)

There is documentation of pH/parameter tests (see attached PDF). The system is not designed to artificially alkalize the water, and the pH remains within natural ranges.
It does not demineralize the water, unlike reverse osmosis systems which must artificially remineralize the water.
For technical decisions, always use water analysis from your area.

See evidence (pH test)

What it does well, what it reduces, and what it is not designed for.

Element / situation	Result	Interpretation Notes	Evidence
Bacteria (E. coli)	REMOVE*	*Under test conditions (laboratory). This does not mean "making any water drinkable" as this depends on many other factors.	2025 Report · Costa Rica Report
Free chlorine (taste/odor)	REDUCE	High reduction reported in the 2025 report (beginning and end of useful life). The INMETRO Framework establishes a minimum certified reduction: ≥75% (Class I).	2025 Report · INMETRO
Particles (≥0.5 µm)	REDUCE	Efficiency depends on particle load, maintenance, and service life.	2025 Report · Fact Sheet
Removable (materials)	COMPLIES	Results of extractables within limits specified in the standard (according to the 2025 report).	2025 Report
Metals / pesticides / organics	REDUCE	There are studies (from Australia, the USA, and the UK) that specify this. However, this information does not replace a chemical analysis of the water if there is a specific suspicion of contamination.	Australia · UK · USA
High nitrates/total dissolved salts (TDS)	NOT DESIGNED	This usually requires other technologies (e.g., ion exchange or osmosis), depending on the case. Nitrates are water pollutants; chemical analysis of the water is recommended if there is a specific suspicion.	—
Non-potable water without analysis	NOT GUARANTEED	Although historically designed to purify water, we now know that a domestic filter does not replace primary water treatment or diagnosis, as it could not guarantee the potability of water in multiple circumstances.	—