EE WAS ATTEMPTING TO WASH DOWN PRESS #7 AND 8 AFTER THEY CAME OFF CAUSTIC CLEANING. WHILE PRESS #7 WAS DRAINING, HE DECIDED TO SECURE PRESS #8. HE WENT BACK TO OPEN OUTLET VALVE AND HOT CAUSTI C STARTED COMING OUT OF THE OPEN DISCHARGE HEADER VENT SPLASHING ONTO HIS NECK AND INTO HIS LEFT BOOT. HE WENT TO SINK TO WASH FOOT, AND SPENT 20+ MINUTES UNDER THE SAFETY SHOWER.