I think the salesman told us 90 liters each tank. When I got my Hoselink water flow meter a couple of years ago I measured the water into the tanks and of course forgot to write it down.
As we are having a couple of weeks away shortly I am making sure van is ready. I decided to measure and calibrate the water into the tanks again. I had to find enough connections to put the flow meter in line as well as have a tap to turn the water off without racing to the tap. I also needed to watch the indicator in the van. I made a pointy piece of stiff wire to hold the test switch, then set Eril's mobile up as a FB messenger video call to my mobile so I could watch the flow meter AND know when each of the indicator LEDs lit up. I did not want to use Facetime as that would use data!!
I had to do some adapting to sort it BUT it worked.