This is one of the reasons it is important to have a septic inspection. This tank is backed up.
This is the outlet end of the septic tank; this picture shows two things. First, the water level in this tank is low which means it leaks. Second, the outlet tee is made of PVC and is in good condition
Here we have an outlet tee that has corroded off, allowing solid waste to enter and clog the distribution box and drain field lines. Repairing clogged field lines entails digging them up, followd by repairing the lawn.
This is the distribution box that the backed up septic tank is sending the effluent to. This box should not be full. There might be a clogged line in the drain field or the there could be a leaking toilet continually feeding the field. A three-bedroom house has a drain field that is designed to handle approximately 360 gallons per day, 120 gallons of effluent per line.
This distribution box should be level, notice water only on one end of the box. This is causing the #1 line to have surfacing issues. (Surfacing is where the effluent comes up and leaves wet areas in the yard.)