Fig. 1. Apparatus used to test the flow system (includes measuring system, water supply system, and water delivery system but excludes core) for repeatability. Inclusion of core allows the apparatus to be used for falling head measurements. The measuring system is limited to the pressure transducers and the cylinder to which they are attached. Pressure transducers P₁ and P₂, mounted on cylinder a distance H_p apart, are used to measure water head in the cylinder. Maximum cylinder fill height was regulated by Mariotte device at H₁. Minimum cylinder fill was regulated to H₃. Manual valve V₂ and automatic valve V₁ regulated water flow. Switch SW energizes control relay R. SW simultaneously opens valve V₁ and sends a signal to the data logger. H is related to total water flow from cylinder.