I have sought legitimate info. regarding the effect of coffee grounds on the function of septic systems for some time.To date, NO SPECIFIC problem directly related to COFFEE GROUNDS has surfaced.

Since all materials which you can visually identify are, by default, "solids", the endless statements that "solids'" enter your septic system and increase the need to pump it out are meaningless! Fecal material DEFINITELY leaves some solids behind after the bacteria have broken down vulnerable organics. Oils/lipids are likely to be more dificult than most organics to break down completely (to digest), and they are established as introducing unique problems, especially related to clump/clog situations. These are best avoided by keeping them, as much as is sensible, out of a septic system. Wiping dinner plates soiled by salad dressing (to remove oil-bearing dressing) is absurd. Dumping used oils from your car is deadly.

Otherwise - all visible materials add small amounts of solids. So what ? All septic systems must be pumped every few years (depends on household specifics). When it comes to solids, the RELATIVE contribution of any material is what matters - for solids.

Poisonous, or otherwise ant-microbial substances are an entirely different concern. Coffee/coffee grounds are not usually considered, "poisonous"! They do offer a chemical intrusion in that grounds are normally acidic. But the amount of acidity in the grounds from any household coffee pot is minuscule when compared to the receiving contents of a septic tank!

So, please feel free to challenge my comment - I TRULY WANT TO KNOW IF THERE IS A SPECIFIC PROBLEM.

"Coffee grounds from a usual home pot are NOT significant
positive/negative inputs for a septic system."

No generalizatios!! We are considering coffee grounds. No philosophy - "it cannot hurt to be extremely protective" - of course it can! All actions have a +/- trade-off. Consider that in specific circumstances (handy-cap, wheel chair, , limited access, - not YOURS), "simply" scraping grounds into a garbage compactor, or dumping them into garden or compost areas, is quite complicated and requires a trade-off vs some other critical activity..

Do coffee grounds introduce unique chemical/poison problems into a septic system? Seems unlikely.

KI.Keating, Ph.D. (Emeritus) Prof. Env. Sci.