Hi,
Did you have any joy with the system. I'm getting the same F7 error amd red error warning light. I changed the 5 amp fuse and the error went away for a while but now it's back. Its a strange one because everything seems to running fine.
Forgot I had posted this, but 3 years on and its still the same. Ive had to replace pump and I clean out tank every year now. I keep a pretty consistent eye on it, but error code doesn't seem to have caused any major issue