Reported instances of stable nonflow in He II Josephson effect experiments have in most cases been achieved by a flow of liquid helium from one reservoir to another, a flow driven by ultrasonic pumping. We have examined some of the characteristics of this pumping. We confirm that a threshold transducer power is necessary to initiate pumping and find that the threshold power has a temperature dependence of ρsTα, 0<α<1, in the range 1.5K