Sunday 17 July 2011
I had a nasty shock yesterday afternoon while disassembling my housing when I saw some water droplets on the inside of the dome port. There wasn't a lot of water and the leak detector had not gone off - at least not that I had seen.
After drying the outside of the while being careful not to distribute any of the water elsewhere inside the housing or on the camera, I removed the dome port. In addition to the droplets inside the dome port there was some water on the gear sleeve for the zoom but I could not see any water on the lens itself. The port 'O' ring was intact with no nicks that I could see or feel.
Next, I removed the camera from the housing. There was a drop of water on the base of the camera between the camera tray and the camera. I could not see any other water on the camera or elsewhere in the housing.
The locations of the water droplets strongly suggests the water entered through the interface between the dome port and the housing and likely to be from the upper side.
After thinking about it for some hours I believe I understand what happened. During the dive I was photographing spotted grubfish that was letting me get very close. It was perched on a mound of sand (and there may have been rock directly under the sand. As I was taking the photographs, I could feel some resistance as I was pushing the rig forward. I suspect I was pushing the bottom edge of the port shade against the sand/rock. As the water was quite shallow (around 4-5 metres), the pressure differential between the inside and outside of the housing would not have been great and so pushing the bottom edge of the port shade in could have resulted in slighting increasing the gap between the housing and the upper edge of the dome port allowing a few drops of water to get in. This would explain the water on the gear sleeve which is where the entering water drops would first hit. The water between the base of the camera and the camera tray would have got there when I tilted the front of the camera up while rinsing it.
At the moment I have no other explanation for the leak. I will just have to watch it closely on the next dive.