El Niño Is Coming — Is Your Sewer Lateral Ready?

Let's talk about the least glamorous pipe in your house. (Stay with me — this one matters!)

Every San Francisco home has a sewer lateral: the underground pipe that carries everything from your sinks, showers and toilets out to the City sewer main under the street. You never see it. You never think about it. Until the day it backs up into your garage or basement... and then it's ALL you think about.

This winter, that pipe is about to get a serious workout.

Why This Winter Is Different

Forecasters are expecting a very strong El Niño this year. NOAA puts the odds above 90%, and there's a better-than-two-in-three chance it becomes the strongest El Niño since record-keeping began in 1950. For coastal California, that tilts the odds toward a wetter-than-normal winter, especially January through March.

Translation: lots of rain, landing on our sewer system (and a whole lot of very old private pipes) all at once. If your lateral has cracks, roots, or a partial blockage, a big storm is exactly when you'll find out — the hard way.

Who's Responsible for What? (Spoiler: Mostly You)

This one surprises a lot of my clients. Your lateral has two parts:

1. The upper lateral runs from your house out toward the street. The City considers it an extension of your home, so it's 100% the owner's responsibility. That means keeping it clear, and repairing or replacing it to current SF Plumbing Code if it's in bad shape.
2. The lower lateral runs from there to the sewer main. You're still responsible for keeping it clear (jetting, camera inspections). BUT — here's the good news — if your plumber finds a structural problem, call 3-1-1 or submit a request at sf311.org. The SFPUC will send a crew to inspect it, and if it needs repair or replacement, in most cases the City handles the work at no extra cost to you. WOOT! (One of my favorite little-known SF homeowner perks.)

The SFPUC's sewer lateral guide has a great diagram showing exactly where one part ends and the other begins.

What a Sewer Lateral Inspection Actually Looks Like

Painless, I promise. A plumber feeds a small camera through the line and records video of the inside. They're looking for:

• Cracks, breaks, or joints that have shifted
• Tree roots working their way in (our beautiful street trees are thirsty!)
• Grease buildup and blockages
• Corroded, sagging, or collapsed sections

You walk away with a report and video you can keep for your records or share with a buyer. And if you own an older home — a Mission Victorian, a Noe Valley Edwardian, a 1930s house in the Sunset or the Richmond — that pipe may be just as old as the house. Worth a look.

Sellers: Do This BEFORE You List

San Francisco doesn't require a lateral inspection when you sell, but I recommend it to my sellers, and here's why:

1. No surprises in escrow. If the buyer's inspector finds a cracked line mid-escrow, you're suddenly renegotiating, giving credits, or watching a nervous buyer walk. Find it yourself before listing, and YOU control the fix, the timeline, and the cost.
2. Buyer confidence. A clean camera report in your disclosure package (right alongside your 3R Report and Natural Hazard Disclosure) shows buyers you've done your homework. Confident buyers write stronger offers.
3. It protects your price. Big unknowns make buyers discount. Known, handled items don't.

And if the camera does find something? Don't panic. Plenty of fixes are simple — clearing a clog, a spot repair. Even bigger jobs are manageable when you have time on your side. That's the whole point of going early.

Buyers: Put It on Your Inspection List

Buying an older SF home this season? Ask for a sewer lateral video inspection as part of your due diligence — and ask whether the seller already has one. It's one of the smartest small checks you can make before you commit.

Your Pre-Storm Checklist

1. Get your lateral scoped if it hasn't been done in a while (or ever!).
2. Find out if you need a backwater valve. Most SF homes are built so a clog near the curb won't back up into the house. But some need extra protection — typically homes where the lowest drain (a basement shower, floor drain, or toilet) sits lower than the lateral's air vent. The SF Department of Building Inspection's backflow preventer page can tell you if your home needs one and how to install it properly, and you may qualify for the SFPUC's Floodwater Grant program.
3. Already have a backwater valve? Service it before the rains start. Debris can keep it from closing when you need it most.
4. Mind your drains. Fats, oils, and grease go in the green compost bin, not down the sink. And toilets are strictly for the "3 P's": pee, poop, and toilet paper. (The City's words, not mine!)

Thinking About Buying or Selling This Season?

If you're planning to list your San Francisco home or you're ready to buy, the lateral is just one of the details I build into my process. For sellers, that means lining up the inspection before we list, so there are no storm-season surprises once we're in escrow. For buyers, it means knowing exactly what you're getting before you write an offer.

I've got a trusted crew of SF plumbers, inspectors, and contractors ready to go. When you're ready to make your move, reach out to me directly. Stay dry out there!