Oh well! The water bladder sprung a leak. After filling the bladder before the last trip to the Flinders Ranges there was a bit of a gush of water from underside of the vehicle. I assumed that the bladder had sprung a leak - it continued to dribble out from underneath for most of the 3 week trip, but still providing a dribble out of the tap - enough to brush teeth or rinse the hands.
After several trips now with running water from the tap at the back of the vehicle I have come to really enjoy the water bladder, so I decided to repair the bladder and improve the holding capacity of the radio accessories storage box in which it was installed.
The plan was to remove the box and its frame from behind the bulkhead, line the area with some unicell foam which was left over from the shed insulation exercise and reinstall the box with the bladder nicely protected inside. The absence of the frame should allow the bladder to inflate as it was designed, without being creased and constrained by the frame.
Once we got the box off, it was obvious that the top of the frame would be beneficial to provide support and negate the need to install some aluminium channel. So we simply removed the frame legs and left the top of the frame. Alter I finish polishing the sharp edges, I will line the bulkhead, sides and floor with the insulation foam, plus do same to the box and around the remaining frame section before re-installing the repaired bladder and box. Below is how the frame looks now with legs removed.