What was found
(CAN) AT 10,000 FEET THE STANDBY ALTIMETER WAS READING 400 FEET LOW. INVESTIGATION FOUND THE STANDBY STATIC LINE DRAIN LINE FULL OF WATER. THE LINE WAS FOUND SPLIT & THUS LEAKING, OPEN TO CABIN PRESSURE. THE SPLIT IN THE LINE IS CONSISTENT WITH DAMAGE CAUSED BY WATER FREEZING IN THE LINE. THE LINE PN 83410474-001, AIPC 34-11-00, FIG 10-340 WAS REPLACED & THE STANDBY STATIC LINES PURGED & LEAK CHECKED. A PREVIOUS SDR 20150106001 WAS SUBMITTED FOR THE SAME ISSUE ON A DIFFERENT TAIL.