massive ships take huge amounts out into the north sea and pump it out there ....also there are 20,000 sewage pipes all around the UK pumping out neat crap for between 8 and 24 hours a day ....emergency overflow pipes they call them . But when checked , were found to be pumping out nearly all the time , and those that weren't were just pumping at night !!! I wonder why ?
Before automatic washing machines came about , septic tanks hardly ever needed emptying . Also many people now have a bath every day , or stand in the power shower forever !!! Huge amounts of water are now pumped into the tanks , they were never meant to cope with this much water .
Divert all your waste water for a day and see how much goes down the pipe....you will then realize why they fill up so fast. That isn't a dig at anyone .. just a fact !!!
cheers
Russ