Can anyone give me some insight on using the pump system?
I have successfully designed and installed many Septic Tank Effluent Pump (STEP) Systems in my 27 years in the septic system business. This type of system is highly reliable. Locate the septic tank so that the raw sewage flows by gravity to the tank for primary treatment and separation of the solids from the liquids. Only the septic tank effluent is pumped to the leach field site. In my view, this is a better approach than using a grinder pump.
Typically, I do not design duplex pump systems. My experience has been that if one uses a high quality effluent pump, the service life is between 15 and 20 years, and a replacement pump is readily available. I design the systems so that it is a simple procedure to replace the pump when it does eventually fail. I also provide a detailed operation manual, that is specific to a particular system, which describes the procedure for replacing the pump, and describes the other maintenance requirements of the system.
If the electrical distribution system in the area in which you are interested has a history of being very reliable, then a battery operated back-up system is also not necessary in my opinion. It is especially not necessary if the home is served by an onsite well. If the electricity is interrupted, the well pump and/or pressure pump will not be functional, and therefor no sewage will be generated.
Is this okay or should I forget this lot and move on?
I agree with Oscar on one point, if you like the lot, go for it.
John Aldrich (Septic Tank Yank)
Septic System Consultant
Timnath, Colorado USA