The fact that a septic drain field would require pumping would indicate that the system is having problems. Pumping with a 2 ½ inch suction line will most likely get plugged with solids.
Where there is a will there is a way. The septic tank drain field can be pumped out; it’s just not going to be an easy job. My best advice would be to leave any type of septic tank or drain field pumping to the professionals.