When to have your septic tank emptied depends on the size of the tank and how many people are residing in your residence as well as how old your tank is and what shape it is in.
The Septic Tank is a key component of the septic system which may include pumps, alarms & sand filters (for gravity fed fields) these liquid effluent disposal methods are called a septic drain field or pond.
Periodic preventative maintenance is required to remove solids that remain and gradually fill the tank, reducing its efficiency.
Avoid issues like the build-up of solids flowing over into the liquid side of the tank, this could cause issues such as plugging up or breaking your submersible pump and eventually damaging your septic field if solids are pumped into your field.
Check to see if you have a leaking toilet or faucet and check your water softener so it does not cycle water every day, you should not have any unnecessary volumes of clear water going into your field.
When buying or selling a house you should get a written report about your septic tank so you can let them know how well your tank is working, the size of your tank, walls of tank and divider wall have any deterioration, if it has a pump out system or gravity system that pumps out effluent to your field.