This specification establishes the minimum requirements for the hydrostatic resistance or "waterproofness" of fabrics coated with rubber or plastics. This document does not cover water repellency or water resistance of the same materials. The test specimens should be cut to specifications and at random from a roll of coated fabric. The hydrostatic tester should be able to apply the required amount of pressure and sustain it for a specified time. The apparatus should be equipped with two concentric ring clamps with rounded inside edges to avoid cutting the specimen. The lower clamp should be fitted with a seal to prevent leakage during testing.