Expert: Dan Griffin - 2/19/2011

Question
Hello.  I was researching some information on our mound system, built five years ago, since our pump just failed.    Every system diagram I show has the septic tank, pump, then field.  Our is reversed - the pump station is there (coming directly from the house), than the septic tank, then field.  Can you think of a reason why it is backwards?  Thank you!

Answer
Cindy,  Conventional septic systems do not use a pump.  They gravity flow from the house to the tank, and the tank to the lateral or leach field.  The mound system raises the lateral field above the gravity level.  This requires pumping the liquid after the septic tank to distribute the effluent in the raised lateral field.

If you have a basement you might have a sewage lift station that raises liquids and solids up to the septic level.  This would be the only reason I could see for having a pump before the septic tank.  

The physical location of the septic tank and the dosing tank could be reversed as long as the actual piping sends solids to the septic, digests and holds solids, and sends the liquid effluent to the pumping station.  By keeping the dosing tank close to the house, the electrical runs are shorter and it may have been easier to install and route piping to the mound.

I know this has not been an answer, but these would be the only conditions that I can envision.