Inside the house
1. Multiple slow drains — not just one.
2. Gurgling toilets or tubs after flushing or running water.
3. Sewage smell near floor drains or the lowest-level shower.
4. Toilets that flush sluggishly even after plunging.
5. Backups in the lowest bathroom (basements, downstairs powder rooms).
Out in the yard
6. Bright green stripe of grass over the drain field — even in a dry Houston summer.
7. Spongy, wet spots near the tank or field that don't dry out.
8. Standing water or sewage smell over the field.
9. Tank lids visible or sinking (settling soil).
10. Aerobic alarm light or buzzer on the control panel.
What to do next
Stop running water if you see a backup or pooling. Schedule a pump-out and inspection — most issues are just an overdue tank, but the only way to know is to look. Don't pour 'septic treatment' chemicals down the drain hoping it goes away.