Pictures 3 & 4 show that it was possible to route the hose behind the fridge and out into the "sofa box" without drilling. Cable clips are available in suitable size for both wire and hose.
Picture 5 shows the - cannister ;o) What it dosn't show is that around the hose i have sealed the hole with this black goo, that is used for sealing caravans. And that the wire is sealed by a marine-store thing that is ment for selaing wires routed thrugh the deck, e.g. It's something like a large washer with a threaded collar - on the thread you have a "finger-nut" and inside is a rubber ring. You thread the wire through, tighten the nut at thus compresses the rubber ring tight around the wire. And as you (at least here) are not allowed to have any electrical installations in the same compartment as the gas cannister i found it worthwile to make sure that no gas can leak into the living compartment. Our law about gas installations does however allow a water pump in the gas compartment as the pump is a spark proof thing - and placing the wire connection between the wire mounted on the pump and the wire from the tap inside the caravan and using this marine thing allows me to change the water pump without having to take the whole caravan apart.
But our trip to Jutland in the fall prooved the pump to be very sturdy; on packing at the camping ground i did of course empty the water system, using the pump in the process. Then i disconnected the 2320 v power cable and soon after we drove off. But 4-5 hours later when i was unhitching the caravan i heard a low noise from the caravan; it was the water pump. I had forgot to turn it off and didn't notice it as it stops when i disconnect the 230 v cable. But i starts again when i connect the 12 v cable from the car. It had been running dry all the way home !