Green genie 2000 pond filter leaking?

we have a pond with a pump system that is leaking somewhere and I can't find where. I've checked all the joints and hoses and there all fine. it has a fountain in the middle of the pond Which I thought to begin with was the cause as the wind took the water onto the lawn but I know that's not the issue. the outlet pipe is in the right place and not leaking. has anyone else had this issue and if so how did u solve it? the pump box is clean and free of rubbish but the water coming out of the outlet pump isn't very clean. the pond is very dirty at the moment as it's has no filtration for several months. thanks