Fitting outside shower

A few questions before I can hope to offer a solution;

1) Is the submersible pump only used to fill the onboard tank?

2) If so how is the submersible pump started?

3)  If not do both pumps run at the same time when a tap is opened and the submersible pump is fitted?

4) Do you want to control the outside shower from outside the caravan or is it practical to control it from inside the caravan?

The submersible pump is used to supply water directly to the taps and to fill the on board tank. There is a simple ball fix valve to stop the water entering the tank. There is a switch on the wall that controls either the external pump or the on board tank. We want  able to control the outside shower from the outside. Problem as I see it is that the external pump or the onboard pump are controlled by the taps. (Microswitches)  do you know of a method of fitting a micro switch in line with the shower. 

Does your outside shower connection point have a valve to close it when there is no shower attached?

If it has, you could fit an inline pressure switch in the internal feed pipe and use a shower head with a built in "tap".

If it doesn't  you will have difficulty anyway because water will flow out whenever you turn on any tap!

Simple solution is to fit an extra long shower flexible pipe, with a trigger fitting on the end, and use it through the bathroom window outdoors. It’s what we did for years in our van. Shower off from beach outside, shower down dogs, etc….. 

I seem to remember that we had a caravan where the custom outside shower head had an inbuilt switch that energised the pump when the trigger was depressed or the head was plugged in. Looking at the photo of the outlet it looks as though there are contacts on the fixed part of the ‘van that control the pump when the shower is plugged in, is this the case? If you’re not planning to use the custom shower head I can’t see how you’re able to get a seal between the outlet and the head. IfI’m missing the point ignore the above. The switch that energised the pump doedn’t have to be a micro switch and can be any switch wired in parallel with the existing micro switch circuits. Hope this helps.