my water pump is flattening my caravan battery?

Do you mean everytime you connect the pump to the internal socket it immediately starts pumping? If so then
I might suggest that the pump socket inside has been wired wrong I have suspicions that the live side of the pump has be fitted to a live FEED wire and not in the isolation side of the pump wiring. Isolation meaning the dead side when pump main switch is in the off position.To test, switch the pump master switch off and see if the pump continues running on that socket, that would prove it's wired wrong. However if it's an occasional fault then it must be shorting somwhere along the line.
If none of this is of help then try contacting www.truma.com [German firm] click on the British flag on left then email them with your problem.
Of course see if the internal system has a pressure valve fitted if so it might be that that's causing it.
You booklet should tell you how to adjust it but in case it doesn't and I hope I'm right try the following.
1 set up pump and barrel.
2. Turn all taps off.
3. Turn on 12 volt system and of course pump main switch.
4. Turn knob on top of pressure valve clockwise the pump will run/be running.
5. Open one tap 1/4 turn then turn pressure valve knob Anti-clockwise until you hear it 'click' stop turning turn off the tap then after around 5 secs the pump should stop.
We'll all be gratefull if you post the solution to you problem.

Bob
July 2008