Crusader george wrote:
Our septic tank backed up. Popped the top and a think "cake" floated on
top of the first chamber. when moved away from the inlet the clog eased.
we had the pumping done. but you know the first chamber was not full.
It had only been three years since pumping. when we bought the place.
The question is what caused this floating mass? It seems full of air.
Could an exceptionally wet year, 163% of normal could be the cause?


Normal. It is a wad of undigested grease, air, plastic. Normal pumping
is about 2-3 years anyway, some do it annually.

If you consider this to be too often to pump, then you need to CLOSELY
examine what you put down the drains. You need to closely examine the
cleaning solutions used in tubs and tiolets. Remove the food disposal
if it is still in place. Wipe all dishes clean into the trash before
using the dishwasher

Web searches turn up LOTS of useful info on this topic