Sewer Backup Causes in Reseda & Van Nuys: 7 Reasons Your Main Line Is Clogged

Published May 8, 2026 • BBC Rooter & Plumbing • Northridge, CA

A sewer backup is one of the worst things that can happen to a home. Raw sewage flooding your bathtub, shower, or floor drains isn't just disgusting — it's a health hazard, and the cleanup costs can run into the thousands. If you live in Reseda, Van Nuys, or anywhere in the San Fernando Valley, the odds are higher than you might think. Most Valley homes were built between the 1940s and 1970s, and the original sewer laterals connecting them to the city main are now 50 to 80 years old.

At BBC Rooter & Plumbing, we clear sewer backups across the Valley every week. Here are the seven causes we see most often — and what you can do about each one before it ruins your weekend.

1. Tree Root Intrusion

This is the single most common cause of sewer backups in Reseda and Van Nuys. The Valley's mature street trees — ficus, magnolia, camphor, and California pepper trees — have aggressive root systems that can travel 30 feet or more to find moisture. Your sewer lateral is a perfect target: a warm, wet pipe full of nutrients, often with hairline cracks at every joint.

Once a root fiber enters a crack, it expands rapidly and forms a dense mat inside the pipe. That mat traps grease, paper, and debris until flow slows to a trickle — then stops entirely. We've pulled root masses out of Valley sewer lines that were three feet long and completely solid. Learn more about which Valley trees cause the worst root damage and how we remove them.

2. Grease Buildup

Cooking grease goes down the kitchen drain as a warm liquid. By the time it reaches your sewer lateral — especially a 60-year-old clay pipe with rough interior walls — it's cooling and solidifying. Over months and years, grease accumulates into a waxy coating that narrows the pipe's diameter. Combine that with a few root fibers and you have a complete blockage.

This is especially common in Van Nuys and Reseda homes where the kitchen drain connects to the main sewer line through a long run under the house. Hydrojetting is the only reliable way to strip grease from pipe walls — a standard drain snake just punches a hole through the clog that reseals within weeks.

3. Bellied (Sagging) Sewer Line

A belly in a sewer line is a low spot where the pipe has sagged due to soil settlement, shifting, or poor original installation. Water and waste pool in the belly instead of flowing downhill to the city main. Over time, solids accumulate in the low spot, and you get recurring backups that no amount of snaking permanently fixes.

Bellied pipes are extremely common in the Valley because of our expansive clay soils. During wet years the soil swells and pushes pipes upward; in drought years it contracts and lets them sag. A sewer camera inspection is the only way to confirm a belly — you can't diagnose it from the surface. If the belly is severe, the sagging section needs to be replaced, often with a spot repair that only requires a small excavation.

4. Collapsed or Cracked Pipe

Clay pipes, which are the standard in most pre-1970 Valley homes, become brittle with age. Cast iron pipes from the same era corrode from the inside out until they develop holes or collapse entirely. When a section of sewer line collapses, there's no channel left for waste to flow through, and a backup is inevitable.

We see collapsed pipes most often in homes built in the 1950s in Reseda and Van Nuys — these neighborhoods were built rapidly during the post-war housing boom, and the clay laterals are now 70+ years old. If you have an older home with recurring backups, read our guide on when cast iron and clay sewer pipes need replacement.

5. Offset Pipe Joints

Older clay sewer pipes were installed in 3- to 4-foot sections joined with mortar. Decades of soil movement, earthquakes, and root pressure push these joints out of alignment — creating a ledge inside the pipe where debris catches and accumulates. A single offset joint can cause chronic slow drains that eventually escalate to a full backup.

Minor offsets can sometimes be managed with periodic hydrojetting. Severe offsets — where the pipes are misaligned by half an inch or more — typically require trenchless pipe lining (CIPP), which seals the joint from the inside without digging up your yard.

6. Flushing Things That Don't Belong in a Sewer

Your sewer line is designed to handle human waste and toilet paper — that's it. So-called "flushable" wipes are one of the biggest causes of sewer blockages we see. They don't break down the way toilet paper does, and they snag on roots, joint offsets, and rough pipe walls. Other common culprits include feminine hygiene products, paper towels, cotton swabs, and dental floss.

This is a factor we can address without any pipe work at all. If your household switches to a strict toilet-paper-only policy and you stop putting grease down the kitchen drain, you'll eliminate two of the top three causes of sewer backups.

7. City Main Sewer Issues

Sometimes the backup isn't your fault at all. The City of Los Angeles maintains the public sewer mains that your lateral connects to, and these mains can overflow during heavy rain events or develop their own blockages. When a city main backs up, sewage can reverse-flow into your home through the lowest drain — usually a floor drain, shower, or bathtub in a ground-floor bathroom.

If multiple drains in your home back up simultaneously and your neighbors are having the same problem, the issue is likely in the city main. Call LA Sanitation at 1-800-773-2489 to report it. If only your home is affected, the blockage is in your private lateral — and that's where BBC Rooter comes in.

How to Prevent Sewer Backups

You can't stop a 70-year-old clay pipe from aging, but you can dramatically reduce your risk of an emergency backup with a few proactive steps:

• Get a sewer camera inspection. This is the single most valuable step. For $150–$350, we run a high-definition camera through your entire sewer lateral and show you exactly what's inside — roots, grease, bellies, cracks, and offset joints. You'll know what you're dealing with before it becomes an emergency. Here's what to expect from a sewer scope.
• Schedule annual hydrojetting if roots are present. Hydrojetting blasts roots and grease out of the pipe with 4,000 PSI water pressure. For homes with known root problems, an annual cleaning keeps the line clear year-round.
• Know where your sewer cleanout is. The sewer cleanout is the access point plumbers use to clear your main line. Many older Valley homes have buried or missing cleanouts, which means a backup requires pulling a toilet to access the line — adding time and cost to every service call.
• Don't pour grease down the drain. Let it cool in a can and throw it in the trash.
• Stop flushing wipes. No exceptions, regardless of what the package says.

When to Call a Professional

If you notice any of these warning signs, don't wait — call BBC Rooter & Plumbing at 818-280-9135 before the situation gets worse:

• Multiple drains backing up at the same time
• Gurgling sounds from toilets or drains when you run water elsewhere in the house
• Sewage smell coming from drains or your yard
• Water backing up into your bathtub or shower when you flush the toilet
• Wet spots or unusually green patches in your yard over the sewer line path

These signs mean the blockage is in your main sewer line, not a branch drain. A drain snake from the hardware store won't reach it, and chemical drain cleaners can actually make things worse by corroding already-weakened pipes.

Frequently Asked Questions

What is the most common cause of sewer backups in Reseda and Van Nuys?

Tree root intrusion is the number one cause. Reseda and Van Nuys have mature street trees — ficus, magnolia, and pepper trees — whose roots seek out hairline cracks in aging clay and cast iron sewer laterals. Once inside, roots form dense mats that trap grease and debris until the line backs up completely.

How much does it cost to fix a sewer backup in the San Fernando Valley?

A simple hydrojetting to clear a blockage typically costs $350–$800. If the line has structural damage — a belly, offset joint, or collapsed section — a trenchless repair runs $4,000–$12,000 depending on length and depth. A sewer camera inspection ($150–$350) is the best first step to know exactly what you're dealing with before committing to a repair method.

Can I prevent sewer backups in an older home?

Yes. Schedule a sewer camera inspection to know your pipe's current condition. If roots are present, annual hydrojetting keeps them in check. If you have a cleanout, make sure it's accessible and the cap is intact. Avoid pouring grease down kitchen drains, and never flush wipes — even those labeled flushable. These steps won't fix structural problems, but they dramatically reduce the chance of an emergency backup.

Should I get a sewer inspection before buying a home in Van Nuys?

Absolutely. Most homes in Van Nuys were built in the 1950s–1970s with clay or cast iron sewer laterals that are now 50–70 years old. A pre-purchase sewer camera inspection costs $150–$350 and can reveal thousands of dollars in hidden damage — collapsed sections, root intrusion, or bellied pipes — before you close escrow.