Water resistance can be measured by two different methods. One is the low hydraulic pressure test, JIS L 1092 A/ISO 811. This test is used to measure water resistance up to 2,000mm, approx. 3 psi. The pressure gradient for this test is 600mm pressure rise/minute. This test is commonly called the “water column test” and can simulate the pressure applied by a column of water up to 6 feet high.
The second method is called the “high hydraulic pressure test”, JIS l 1092 B. This test is used to measure from 2,000mm to as high as 30,000mm. The pressure gradient for the test is 10,000mm pressure rise/minute.
Each method uses different equipment to measure water resistance. Both methods apply pressure, by water, to the fabric until the fabric begins to leak. In both tests you don’t consider it a leak until there at least 3 distinctly different drops coming through the fabric
The primary difference between the two methods is the rate at which water pressure is applied to the fabric. Many technicians feel that exposure to the artificial situation created by machines is not realistic after the fabric has been on the machine over 3 minutes. Therefore, some testing may require a wire mesh screen to achieve a more realistic testing situation.
The maximum pressure I use to test silnylon or Cuben is 3,515 to guarantee no fabric damage. At this low maximum press no screen needs to be added over the fabric. In addition, my tester has a metal bar that levels-out any pressure bulge.