What was found
FLIGHT 2726, CREW REPORTED DURING DESCENT OUT OF FL370, RECEIVED "IAS" COMPARE FLAGS ON BOTH FIRST OFFICERS AND CAPTAINS PFD. CAPTAIN`S IAS WAS UNRELIABLE, SHORTLY AFTER RECEIVED AN AMBER "ALT" COMPARE FLAGS AS WELL. SELECTED NR 2 ADC ON CAPTAIN`S REVERSIONARY PANEL, EXITED IMC/ICING CONDITIONS AND DIVERTED. AFTER LANDING IN WARMER TEMP DESELECTED ADC REVERSION ALL FLGHT INSTRUMENTS APPEARED NORMAL. COMPLETED AOM VOL 1 CHECKLIST AND DECLARED AN EMERGENCY AND ELECTED TO DIVERT. LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REMOVED WATER FROM CAPTAIN`S PITOT SYSTEM PER MM 34-30-00 AND PERFORMED OPS CHECK PER MM 34-15-00. OPS CHECKED NORMAL. AIRCRAFT RETURNED TO SERVICE.