There's some confusion here.
For a start do you mean a Miniature Circuit Breaker (MCB) has tripped or the RCD - looks similar but has a test button on it?
If it is the RCD that is tripping then you have a wiring problem or a fault on the fridge and it needs to be investigated by an electrician - those sort of faults can be difficult to bottom.
If it is a MCB that is tripping then something is drawing too much current. Look on the front of the MCB that is tripping and see what it is rated - 6A, 10A, or 16A. The 6A usually feeds the 12V power supply or battery charger (whichever your van has,) the fridge, and the water heater; the 10A or 16A (again whichever is fitted) feeds the 13A sockets, the microwave and the room heating. In caravans with Alde wet heating both water and room heating is provided by one unit which will be on the 10/16A MCB. The microwave is usually connected by a 13A plug in the cupboard at the side of it, and if you have such as a Truma room heater that runs off gas or electricity for heating (any fan will be 12V) that too is usually plugged in to a 13A socket somewhere nearby.
As others have said, in most caravans made in the last, say, 15 years or so all lighting, the water pump, cooker spark ignition, radio, and aerial amp all run off 12V. Some modern fridges need 12V to make the control system work even if using mains or gas to do the cooling. Ergo if the water pump is not working then it is a 12V issue.
If the pump is external and drops into you Aquaroll then checking for the presence of 12V on the contacts feeding 12V to the pump (with a tap turned on) will indicate if it is a caravan or a pump problem. If the pump is internal then you probably have a Whale pressurised system in which case there will be a pressure switch that operates the pump somewhere near said pump with a knob on the top to adjust it.
If you don't have one a simple and inexpensive digital voltmeter (DVM) is a great asset with such problems. You can also get a pen-like device which will light up and make a sound when held adjacent to a live mains wire - very useful not least to find out if a plugtop fuse has blown.
Finally talking of fuses, the fridge if it is under counter will draw around 120W, if it is the larger tall type it will pull nearer 170W - and it draws that much power from mains or from 12V when towing. If the fridge is plugged in it should have a 3A fuse in the plug. The microwave will draw about 1.5KW which will need a 13A fuse as will the room heater.
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