idk where the filter is in relation to the pool and your prop line, cant see that from the overhead, but5 the simple answer is to ask him to move it to the unclaimed lot behind your houses. It seems his back/right prop line has more than enough space to do it and its not that much further away from the pool. The fact that the unclaimed lot is even there should be enough grounds for accommodating you, many of us wouldn't even have that option.
I have a similar issue, my neighbor has a laundry machine wash overflow drain that empties onto my property. My property use to be his back in the day, it was a wooded lot that he had for 30 years before having to sell it to my contractor b/c of his divorce. After we built the house he told me about it and asked if it was ok to be there, and if so, to just not cover it with anything while we landscaped. Its in an area I have no plans on using and at most is a gallon or 2 of dirty water every few months. So I dont have an issue with it. We are friendly with him overall so no need to make enemies over a pipe thats been there that long and not bothering me. You cant even see it, its in a small rock wall near the front of my yard..