Overview
EN ISO 811:2018 (Textiles - Determination of resistance to water penetration - Hydrostatic pressure test) specifies a laboratory method to determine the hydrostatic head a textile can support before water penetrates. The standard applies to all types of textiles intended to be water resistant, whether treated with water‑resistant or water‑repellent finishes or not. It is widely used for quality control, product development and conformity assessment of performance textiles.
This method measures the pressure at which water first penetrates a fabric in three places under controlled conditions and reports the hydrostatic pressure (commonly in cm H2O or mbar H2O).
Key Topics
- Scope and principle: A specimen is subjected to steadily increasing water pressure on one side until penetration occurs at three locations; the pressure at the third penetration is recorded.
- Reagents: Use grade 3 water in accordance with ISO 3696. Tests are conducted at either 20 °C ± 2 °C or 27 °C ± 2 °C; the chosen temperature must be stated in the report.
- Apparatus and specimen:
- Fabric clamp that secures a test area (10 000 mm2 / 100 cm2) without bulging or leakage.
- Mechanism to increase water pressure at a controlled rate: either 10 cm H2O/min ± 0,5 cm H2O/min or 60 cm H2O/min ± 3 cm H2O/min. The chosen rate must be stated in the report.
- Appropriate manometer range for the fabric construction and accurate recording as specified by the standard.
- Conditioning and environment: Follow ISO 139 for conditioning and testing atmospheres, unless otherwise agreed.
- Procedure and reporting: At least five specimens from different fabric locations are recommended. Record the pressure at the third penetration (or the first drop if agreed) and include apparatus, temperature, pressure rate and any deviations in the test report.
Applications
- Quality control and batch verification of water‑resistant garments and technical textiles.
- Product development and comparison of finishes, coatings or membrane laminates.
- Supporting conformity claims for waterproofing performance in performance wear, outerwear, tents and protective clothing (with appropriate statistical design for larger datasets).
Practical benefits:
- Provides a repeatable, comparative measure of water resistance (hydrostatic head).
- Helps manufacturers and test laboratories standardize test conditions and reporting.
Related Standards
- ISO 139 - Standard atmospheres for conditioning and testing
- ISO 3696 - Water for analytical laboratory use (grade 3 water)
- EN 20811:1992 - Superseded by EN ISO 811:2018
- Reference: Prepared by ISO/TC 38 (Textiles) and adopted by CEN as EN ISO 811:2018
For test implementation, follow the detailed clauses on apparatus, specimen preparation, test procedure and result expression in EN ISO 811:2018 and reference the normative documents listed above.
