ASTM D2434, Standard Test Method for Permeability of Granular Soils (Constant Head) (Withdrawn 2015) , and ASTM D5856, Standard Test Method for Measurement of Hydraulic Conductivity of Porous Material Using a Rigid-Wall, Compaction-Mold Permeameter , are used to measure the saturated hydraulic conductivity, K sat , of soil specimens in rigid-wall permeameters (RWPs). Several laboratory conditions and settings explain why the tests do not give K sat values but unsaturated hydraulic conductivity, K ( S r ), values for a degree of saturation, S r , that is often in the 80-85 % range. It is suggested to improve ASTM D2434 and ASTM D5856 by adding two requirements: (1) use a watertight-and-airtight RWP (a control method is provided), and (2) use a mass-and-volume method to obtain the true S r value of the tested specimen. To illustrate potential detrimental impacts of current standards, the article describes a case where sand was planned to be used as a filter layer for a solid waste project. Large quantities of sand had been delivered at the construction site. The K sat value of the sand, as compacted, had to exceed 10 -4 m/s to satisfy a bylaw. To prove this, two laboratories followed ASTM D2434 for their tests but found K values of 5-8×10 -5 m/s. The project engineers asked the authors to make verifications. The prior tests were redone and yielded similar K values. However, it was found that the real S r value was close to 80 % instead of being assumed to be 100 %. Other tests were performed after using vacuum and deaired water in a watertight-and-airtight permeameter: the specimens reached S r =100 % and gave K sat values of about 2×10 -4 m/s, 3-4 times higher than initial tests. As a result, the already delivered sand satisfied the bylaw condition and there was no need to return large quantities of sand already delivered, to purchase a new type of sand after having done laboratory tests, and to have a time delay in construction, all these items having a high economic impact.