Main sewer line partially clogged

Quick Answer:

If several drains gurgle while you run the washer, you likely have a partial blockage in the main sewer line rather than a broken pipe. Check the house sewer cleanout, open the cap slowly to watch for pressure or backflow, and run a few fixtures (toilet, tub, laundry) to confirm it’s affecting the whole house. If a professional-grade auger through the cleanout doesn’t restore normal flow or debris returns, book a sewer camera inspection to look for roots or cracks.

Why This Happens

When multiple drains act up at once — gurgling, slow draining, or backing up when the washer runs — the obstruction is often at the main sewer connection where household waste leaves your property. Common causes are tree roots pushing into joints, a buildup of grease and solids, or partial collapse at an old joint. Small or intermittent blockages let some flow through but cause air and water to back up, which produces gurgling sounds and sporadic slowdowns.

If you’re seeing symptoms across fixtures, consider reading about Slow drainage in entire house and Partial clog causes random backups for more background on how these problems show up.

Step-by-Step What to Do

1. Confirm the problem by running several fixtures

• Run the washing machine and flush a toilet while the washer drains.
• Run a tub or sink on another floor at the same time. If all show slow draining, gurgling, or backflow, it points to a main-line issue rather than a single fixture.

2. Locate the house sewer cleanout

• Cleanouts are usually an above-ground capped pipe near the foundation, driveway, or in the yard along the sewer route. They may also be in a basement floor or utility area.
• Clear any debris around the cap so you can access it safely.

3. Open the cleanout cap slowly and check for pressure

• Have a bucket and rags ready. Wear gloves and eye protection.
• Loosen the cap slowly to let any built-up gas escape. If the line is pressurized you may see water or sewage rise near the cap — step back and stop if you get a strong flow.
• Minor bubbling or a small amount of backing water confirms the clog is in the main line.

4. Try to clear the clog from the cleanout with a professional auger

• Use a professional-grade drum auger or sectional rooter sized for sewer lines rather than a handheld closet auger.
• Feed the auger through the cleanout toward the street (downstream) — that follows the flow and reduces risk of pushing debris back into branch lines.
• Work slowly, feeling for resistance. If you break through roots or grease, you may get improved flow. Pull the auger out carefully and clean any debris from the cleanout area.

5. Re-check flow and decide next steps

• Run the washer and other fixtures again. If normal flow returns and stays clear, continue to monitor.
• If you see reduced flow at the cleanout, debris keeps returning, or problems recur shortly after clearing, schedule a sewer camera inspection to locate roots, cracks, or collapsed sections so they can be repaired correctly.

What Not to Do

• Avoid pouring chemical drain cleaners into the main cleanout. These products are designed for small interior drains and can be dangerous and ineffective in the main sewer, and they can harm sewer lines and the environment.
• Do not repeatedly run fixtures to try to force water through a suspected main-line clog. That can push sewage into the house or make a partial backup worse.
• Call a professional when snaking from the cleanout doesn’t restore normal flow, if you detect sewage at floor level, or if the problem recurs soon after clearing. These are signs of roots, cracks, or collapse that need experienced diagnosis and repair.

When to Call a Professional

• Visible sewage at floor level, persistent backups, or foul odors that won’t clear — treat these as urgent and call a plumber immediately.
• If a rooter or auger does not restore normal flow, or the clog returns within a few days, arrange a sewer camera inspection so the technician can locate roots, offsets, or holes that need repair.
• If you are uncomfortable opening the cleanout or using a professional auger, call a licensed plumber rather than attempting risky repairs yourself.

Safety Notes

• Wear gloves, eye protection, and old clothes when opening the cleanout. Sewage contains harmful bacteria and chemicals.
• Open the cleanout cap slowly to release pressure and gases safely. Step back if a forceful flow appears.
• Never enter a confined space or trench without training. Avoid direct contact with sewage and wash hands and tools thoroughly after working.
• Use the correct tools: a professional-grade auger for sewer lines, not a household closet auger. If nearest help is needed, call a licensed plumber.

Common Homeowner Questions

• Is this an emergency? If sewage is backing into the house or you smell strong sewer gas, yes — call a plumber right away.
• Can I fix this with a plunger? A plunger helps small blockages in single fixtures but usually won’t clear a main-line partial clog affecting several drains.
• How long before I need a camera inspection? If clearing from the cleanout doesn’t hold or debris returns quickly, arrange a camera inspection as the next step to find roots or pipe damage.

More in this topic

For more related fixes and similar symptoms, see Main Line Partial Clogs.