ABSTRACT
This chapter deals with the infiltration, weep and stiffness modes of long-term failure. It focuses on the weep threshold. The regression weep lines of commercial pipes derive from the ASTM D 2992 B test protocol, which monitors the onset of weeping in pressurized water-filled pipes. The constant test pressures are higher than the weep threshold, otherwise the pipes would never weep. The cracks that develop in the pressurized specimens are stationary, and the times to weep are a function of the applied pressure, or strain. Substantial improvements to the pipe's weep threshold come from the use of tough resin matrices in the critical ply and, of course, the use of aluminum foil. The weep threshold of the critical ply is a better indicator than the onset of pipe linearity. The classical HDB derives from a false assumption combined with a meaningless variable. The false assumption is the growth of stationary cracks.
