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How to clear a main line clog

We'll clear the main line clog using a drain snake—or tell you when to call a pro.

How-to · Home plumbing
30–90 min
What you'll need
  • Drain snake (25–50 feet for main line; hand-crank or electric)
  • Wrench (for cleanout cap)
  • Bucket and towels

At a glance

  • Confirm it is a main-line clog—water backs up from multiple fixtures when you run one.
  • Locate the main cleanout (usually outside or in the basement) and remove the cap.
  • Feed a drain snake into the cleanout toward the street or septic; crank when you feel resistance.
  • If the snake will not reach or the clog persists, call a plumber with a sewer camera and auger.
  • Never use chemical drain cleaners in the main line—they can damage pipes and are ineffective on solid clogs.
Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Clear the main line clog so all fixtures drain.

  • Confirm it is a main-line clog—multiple fixtures back up. Locate the cleanout.
  • Good: Cleanout is found. Proceed to Open and snake.
  • Bad: No cleanout—call a plumber.

Open and snake

Goal: Access the main line and feed the snake.

  • Remove the cleanout cap. Feed the snake into the line toward the street or septic.
  • Good: Snake is in the line. Proceed to Crank and clear.
  • Bad: Water pours out—let it drain, then snake.

Crank and clear

Goal: Break through the clog.

  • Crank when you feel resistance. Feed and crank. Pull back if you hook debris.
  • Good: Resistance gives way. Proceed to Test and cap.
  • Bad: Snake hits a hard stop or will not reach—call a plumber.

Test and cap

Goal: Verify drains work and replace the cap.

  • Run water in multiple fixtures. Replace the cleanout cap.
  • Good: All fixtures drain. Proceed to Verification.
  • Bad: Backup persists—call a plumber.

When to get help

Call a plumber if:

  • You cannot find the cleanout.
  • The snake will not reach the clog or hits a hard stop.
  • The backup persists after snaking.
  • You smell sewage or see raw wastewater (possible sewer line break).

Verification

  • All fixtures drain without backup.
  • No backup when running multiple fixtures at once.
  • Cleanout cap is secure with no leaks.

Reviewed by Blackbox Atlas

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