Water On Runway Flips Tri-Pacer

June 8/14-The conventional gear Piper PA-22 (C-FHLW) had completed a low pass to evaluate conditions before landing at the private grass runway in Gypsumville, MB. Upon landing the aircraft overturned when the main wheels touched down in the standing water at a speed of approximately 45 mph. The standing water on the threshold had not been observed from the air due to the length of grass (6 to 8 inches tall). The pilot, the sole occupant, evacuated through a rear exit door and sustained no injuries. The aircraft sustained substantial damage. There was no post-occurrence fire. Approximately 2.5 inches of rain had fallen in the area two days prior to the occurrence.