In France, if you have a septic tank, then it's supposed to get checked every four years to make sure it's working properly, and that you have done the necessary maintenance. Since our system was brought up to date a few years ago, we have had a couple of these checks, the most recent being a week or so ago.
I'm really not sure how these checks are supposed to work. We have been scouting around recently for a smaller place to buy for our eventual retirement proper; many of these places are second homes, used only in Summer, with waste processing systems installed when God was a boy and that can't possibly be up to current norms. One place that we looked at discharges its waste straight into the nearby river, and was lived in until last year. Do they get inspected, and what happens if they don't meet current specs? I have no idea.
Anyway, our checkup detected that the pipework that distributes water between the various arms of the filter bed was no longer horizontal, and was sending all the water down one arm. We got the person who installed it to sort it out. We have been impressed with everything he did here during the renovations, and his prompt response to our request for help is yet another plus point on his scorecard.