We bought a house that is 14 years old. It was vacant when we bought it and I peeked at the dosing tank and it was half-full. Since we actually moved it I noticed it was always wet around the cover of the dosing tank, so I pulled the cover and found it full. The full alarm never went off and we never had back-ups. I opened the electrical panel by the tank and found the sensor wires wet and corrode. I cleaned-up the connection and bingo- the alarm started going off in the basement!
In the junction box there was a standard electric plug, but had no power going to it. I found a breaker in the house labeled sewer pump, but it was not tripped. I took an extension cord out and plugged it into the junction box male plug and it tripped the GFCI instantly. So I got smart and plugged it into a non-GFCI outlet and it tripped the breaker instantly.
I plan on having the septic tank and the dosing tank pumped, but I would like to be ready to fix the problem before we fill-up the tank, any ideas?