Leaks a bit while filling. It was a bit gunked up so I removed and cleaned it and I also cleaned the hose leading to the front of the sump but it still leaks. I wonder whether there’s still some gunk in there preventing flow through, or if something else is causing the problem. I notice that there isn’t a seal where the side tank plugs into the pressure chamber but from memory I don’t think there should be. I did read somewhere that this can be caused by a failing inlet valve but I’m a bit sceptical about that.