leaking watertank

Hi, we have a factory fitted diahatsu hijetta van and are getting some leakage from the drinking water tank. Does anyone have any experience of removing it?

diahatsu hijetta drinking water tank....
never had a problem with those

Just renovated mine, I had some leakage of the original setup but it was from the hose connections not the tank due to the hoses being the spiral type and hose clips just were not fitting correctly. The tank itself seems quite robust. Getting to the tank depends on your layout as there are at least three that I know of. One has the sink/cooker across the back door, one has the sink/cooker along the side and the third which I have only seen one, has the sink/cooker under a seat across the middle of the van. Whats your layout?