Holy cow! Get that thing pumped! ASAP.
So here's the deal with septics.
1. Food and human feces are pretty close to the same thing. They are organic and will decompose when given the chance. So people who grumble about disposals are a little off base. However, if you grind up things that are tough to decompose, well...you're just asking for it. But if you put a peanut butter sammich down the drain, the bugs will love it.
2. "Toxins" that you don't want to put into a septic system are anything that's "antibacterial". Stuff like bleach, Lysol, gasoline, grease are all bad ideas. Apples, bananas (not peels), meat, are all fine. Just remember that the more solids you put in there, the sooner you will eventually have to pump it out.
3. Determining the right time interval to pump a septic tanks isn't so easy. Depending on the size of tank, 500 gals, 1,000 gals, it may be years before you who spend all your time in the shitter at work will need to do it. I'd suggest about a 2 year interval. It costs around $180 depending on who you hire, but that's money well spent when a new drain field will cost you $8-14k. Again, depending on where you live and how greedy the local contractors are nowadays.
4. RidX and all the other additives a person can buy (including yeast) are not needed unless you use a bunch of stuff like bleach that kills off the naturally occurring biologicals in your poop.
5. One danger to a drainfield is the hard to decompose stuff. If you let your tank fill with solids (it will over time), eventually those solids will end up in your drain field. Those hard to decompose items (coffee grounds, banana peels, paper towels) will plug/line the base of the drain field and inhibit infiltration. That is the death of the drain field, once those pore spaces are blocked by slow to decompose objects, the infiltration rate falls below the rate at which you add water to it. Hence your tank fills up, alarms go off, and you have to have someone come out and install a new drain field.
6. Egg shells are primarily CaCO3, calcium carbonate. CaCO3 readily dissolves in acids. Most any septic tank with a sewer gas smell is plenty rich in H2S. H2S is a weak acid, egg shells don't stand a chance in an environment dominated by H2S.
shorthairman, again...pump your tank!
