Historical
BS EN 20811:1992
Textiles. Determination of resistance to water penetration. Hydrostatic pressure test (British Standard)
A specimen is subjected to a steadily increasing pressure of water on one face, under standard conditions, until penetration occurs in three places. The water pressure may be applied from below or from above the test specimen. The hydrostatic head supported by a fabric is a measure of the resistance to the passage of water through the fabric.
British Standards Institution [bsi]