Can you see the area behind the potty? Can you see where the water line comes out (i.e. from the floor or the wall)?
Its possible there is a fitting that is leaking in the hollow space under the "step", or you might have an internal leak in the toilet itself, or it could be that the leak is elsewhere and the water just finds an easy path out that way.
With no faucets turned on, does your water pump cycle on and off? That indicates a leak in the water lines somewhere. If you do NOT hear the pump cycling, its possible that the toilet itself is leaking around the floor flange (*ick*) when flushing.
First, look carefully in the cabinets and under the shower, inside the sewer bay and so on for leaks. If you don't find any, you will have to pull the toilet to check it, probably.
Life rocks when your house rolls
Senior Chief & the Cheese Queen