Quick answer: Stop all water use immediately, keep people and pets away from the sewage, and call a septic company. If only one fixture is affected, it's likely a drain clog (call a plumber). If the lowest drains in the house are backing up, it's usually the septic tank or system.
Clog or septic problem?
| What you see | Likely cause | Who to call |
|---|---|---|
| One sink or toilet backs up, others drain fine | Clog in that fixture's drain | Plumber |
| Basement floor drain or lowest tub backs up when other fixtures run | Main line blockage or full or failing septic system | Septic company |
| Gurgling everywhere, slow drains throughout the house | Full tank, blocked outlet or failing field | Septic company |
| Wet, smelly ground over the tank or field | Tank overflow or leach field failure | Septic company, today |
While you wait for help
- Don't flush, shower, run laundry or the dishwasher.
- Don't use chemical drain openers. They can harm the system and the person who pumps it.
- Keep children and pets away from wastewater. Wear gloves and boots if you must go near it.
- If you know where the tank cover or riser is, mark it so the pumper can find it fast.
- Photograph any damage for your homeowner's insurance.
What the septic pro will do
Usually they pump the tank first, which relieves the backup right away. Then they check the inlet and outlet baffles, the line to the house, and whether effluent flows back from the leach field. Backflow from the field is a sign the field may be failing, which is a bigger repair. See repair & replacement.
Cleanup
Sewage contaminates porous materials like carpet, drywall and insulation. Professional cleanup is often the safest choice for anything beyond a small, hard-surface spill.
Related guides
Frequently asked questions
Is a septic backup covered by homeowner's insurance?
It depends on the policy. Many standard policies exclude septic and sewer backup unless you added a backup endorsement. Check your policy and call your agent.
Can I use the toilet if the septic is backing up?
No. Any water you send down the drain has nowhere to go and can come out at the lowest drain in the house.
How fast can someone pump my tank?
Many septic companies keep openings for emergencies, often the same or next day. Call rather than filling out the form if sewage is actively backing up.
Last reviewed 2026-11-09. Regulations and prices change. Confirm details with your local Board of Health and your contractor.