Permittivity Test
These test methods cover procedures for determining the hydraulic conductivity (water permeability) of geotextiles in terms of permittivity under standard testing conditions, in the uncompressed state. Included are two procedures: the constant head method and the falling head method.

In Constant Head Test: - A head of 50 mm water is maintained on the geo textile throughout the test. The quantity of flow is measured versus time. The constant head test is used when the flow rate of water through the geotextile is so large that it is difficult to obtain readings of head change versus time in the falling head test.

In Falling Head Test: - A column of water is allowed to flow through the geo textile and reading of head changes versus time is taken. The flow rate of water through the geo textile shall be slow enough to obtain accurate readings.
Sample Size: - 50 mm
Head can be maintain of the sample : up to 40 cm
Suitable for Both type of test :- Constant Head and Falling Head.

Meets: - ASTM- D 4491 – 99a, IS-14324