How to Clear a Clogged Main Sewer Line
When your home has multiple drains backing up, it’s the main line. Here’s how to diagnose and what NOT to attempt yourself.
TL;DR
Main sewer line clogs cause multiple drains to back up simultaneously, sewage to come up through floor drains, or toilets to bubble when laundry drains. DIY snake doesn’t reach. Pro hydro-jetting at 3,000–4,000 PSI is the right tool.
What’s in this guide
- Symptoms of main line clog
- Causes
- Why DIY rarely works
- Pro options
If multiple drains in your home back up at the same time, the clog is in your main sewer line — the pipe that connects your house to the city sewer. This is past the point of DIY for most homeowners.
Tools & Materials You’ll Need
Tools
- 25-foot drum auger may help diagnose location
- Camera scope (pro tool only)
- Hydro-jet (pro tool only)
Materials
- Pro-supplied
Step-by-Step Instructions
Confirm It’s the Main Line
Test: flush a toilet, run shower, run kitchen sink. If all drain slowly OR water backs up at toilets when other drains are used, main line is clogged. Single drain backup = local clog (not main line).
Identify the Cleanout
Most LA homes have a cleanout cap — usually visible at the front of the house, under the toilet, or in the yard. Plumbers access the main line through this. If you don’t have a cleanout, you have a much harder repair situation.
Don’t Pour Drain Cleaner
Chemical drain cleaner cannot reach a main-line clog. It just sits in your fixtures and damages the closest pipe sections. Wasted money + pipe damage.
Try a Drum Auger if Cleanout Accessible
A 50-foot rented drum auger ($50/day) might break through a partial clog. If you can locate the cleanout. WARNING: be prepared for sewage spray when you open the cap. Use full PPE.
Call a Pro for Hydro-Jetting
For full clearing of cast iron mains in older LA homes, hydro-jetting at 3,000–4,000 PSI is the only thorough method. Restore the inner diameter, not just punch a hole through the clog.
After thousands of LA main line jobs, the most cost-effective approach is: snake first ($185–$285) for immediate clearing, then camera-inspect ($85 add-on) to identify root causes. If recurring root intrusion or scale buildup, trenchless lining ($4,800–$7,500) prevents repeat issues. The math: $5,400 for permanent fix vs $250 every 6 months for life of home.
Sewage backup is a biohazard
Don’t attempt DIY without full protective equipment. Sewage contains bacteria and chemicals harmful to skin and eyes.
Real Scenarios from Our LA Service Calls
1928 home, recurring backups
Homeowner had been calling for snake service every 6 months for 4 years. Camera revealed three separate offset joints with active root intrusion. Trenchless lining of the 28-foot affected section: $5,800. No further backups in 22 months and counting. Saved $1,200+ in continued snake calls.
When to Call a Plumber Instead
DIY isn’t always the right call. Bring in a licensed plumber if any of these apply:
- ALWAYS for main line clogs — DIY rarely works
- Sewage backup
- Multiple drains affected
- Recurring main line problems
Frequently Asked Questions
How much does main line clearing cost?
Snake: $185–$385. Hydro-jet: $385–$685. Trenchless lining: $4,800–$7,500.
How long does cleared main line stay clear?
Snake only: 6–18 months in cast iron with roots. Hydro-jet: 24–36 months. Trenchless lining: 50+ years.
Why does my main line keep clogging?
Most common: roots intruding at offset joints. Second: cast iron pipe scale. Third: pipe damage requiring replacement.
Can I prevent root intrusion?
Annual root foam treatment can slow regrowth but doesn’t fix offset joints. Trenchless lining is the only permanent fix.
My city has a backup — what then?
City backups (their main, not yours) are LADWP’s problem. Sewage on your property from a city backup may be claimable.
Need professional help in Los Angeles?
Same-day service. Flat-fee pricing. No surprise add-ons.
Call (818) 938-8660
