A steam autoclave for treating Regulated Medical Waste that uses a condensate drainage system that provides for condensate drainage while the steam autoclave chamber remains pressurized during the steam treatment cycle to create pressure variations in the autoclave which are used to initiate the introduction of repeated bursts of steam into the waste during the steam treatment cycle. The repeated bursts of steam into the autoclave during the steam treatment cycle agitates the steam and waste contained in the autoclave, thereby enhancing steam penetration into the waste being treated and thereby enhancing biological kill efficacy.