Abstract: A sub incorporating a check valve is connected into the lower end of a well pipestring. This valve will pass hot steam injected down the pipestring to the formations to loosen up the thick crude oil. The check valve prevents back flow and thus will hold the high pressure steam. To resume production, the production pump can then be lowered through the pipestring. The pump itself is provided with an extended probe member which will unseat the check valve when the pump is in proper position so that production pumping can resume.