I also read that the filters should be tossed. I have two houses with them, i put them in myself , they did not come with filters….I think they are called effluent filters….by the time it’s really going to your leach field it should not contain solids. Don’t know. If mine ever does clog i know exactly what to do about it. You can still see where all the leach lines are because it in weeds and they grow better over each line.

Do you know how/where leach field was blocked and what was done about it.

Did you have a universally low functioning leach field, or a block in a pipe somewhere? If it was just a block that got fixed, your field could be fine.