eddy,
You have septic tank/drain field issues.
Silver, chlorine bleach, and other things we dump down the drain do kill/inhibit digestive bacteria, (good bacteria and enzymes) in the septic tank.
The conditions you describe indicate that your septic tank is too full of solids, and/or your drain field is possibly obstructed, or inadequately sized.
Ask your father when last the septic tank was pumped. Five years or more last...pumping will probably be the cure.

You can introduce good bacteria and enzymes, two ways. Commercially available products like the aforementioned 'Rid-X,' or [free] yogurt.
Go to your local grocer/supermarket; ask if they will give you outdated, plain yogurt, or at least sell it at no more then 5-10 cents each.
Flush about half dozen, single serving yogurts a week, or at least twice a month.