The Sewer Lateral: Add it to Your List of Inspections.

February 29, 2012

Man with magnifying glass

Often Overlooked.

Home buyers in San Carlos and throughout the peninsula have grown accustomed to paying to have a home inspected prior to purchasing it — especially in San Carlos, where the majority of homes were built originally in the 1940's and 50's.  Believe me, half a century of hard living can take its toll on a home.   It has become such a standardized practice in real estate transactions, that even the sellers of the home will conduct their own inspections prior to listing it on the market just so that they know what the buyer's inspector is likely to find.  This allows the seller the option to either fix known problems in advance, or adjust the listing price accordingly because of the known anomalies.

The 2 most common inspections that buyers have traditionally done prior to moving forward with the purchase of a house are:

  1. Wood Destroying Organisms Inspection (aka Pest Inspection), and
  2. Property Inspection.

The pest inspection looks for pest infestation, such as termites and beetles, as well as any wood damage caused by water intrusion.  The property inspection is a “catch all” inspection that assesses the overall functionality of the house — from appliances, to electrical distribution to visible plumbing.

With these two inspections, a buyer gets a pretty good idea of the condition of the house that they're contemplating purchasing  There are more in-depth inspections that can be done on the roof, or foundation, or the plumbing system if the property inspector recommends further investigation.  But it's safe to say that most home buyers will only do pest and property inspections before making their decision.

But there's one key function of the house that these inspections don't usually cover — and it's an area can lead to an unwanted surprise and an expensive fix for the new buyer:  The sewer lateral.

What is the Sewer Lateral?

The sewer lateral is simply that single piece of pipe that connects all of the waste lines in your home with city sewer system.  And the reason it hasn't been traditionally inspected until recently is because once the sewer line exits the crawl space of a typical home, it runs underground to its junction with the sewer system, thus making it impossible to visibly inspect the condition of the pipe.   See the diagram below for a typical sewer lateral configuration.

Diagram of a Sewer Lateral Connection

What can happen to this pipe?  In older homes, the sewer lateral is an approximately 4″ diameter cast iron pipe runs under the yard and connects to the sewer main.  Since the pipe is constantly exposed to moisture from both sides, it can corrode over time and start to weaken.  Seismic activity can also compromise the integrity of the pipe.  Either way, once the wall of the pipe is breached, the door is open to all kinds of problems.

The most obvious issue is having raw sewage leaking into the ground below your house, which is not a good thing.   And since there are no telltale signs of this happening, it can go on for a long period of time undetected.   What usually happens when the wall of the pipe is breached is that roots from trees or other plants will penetrate the pipe and ultimately clog it up.  You'll know this has happened as soon as you flush the toilet or take a shower and the whole system backs up.  This is also not a good thing.

A Potentially Expensive Fix.

Depending on which path the sewer lateral takes to connect to the sewer system, repairing this line can be expensive.  Why?  Because if the entire line needs to be replaced, which is usually the case, it requires digging a trench to expose the complete run of the pipe — which can often run right underneath expensive landscaping, or worse yet, under your driveway.    So you can see why knowing the condition of the sewer line is an important piece of information before you take the jump to buy the house.

New Inspection Methods.

Until a few years ago, it was difficult to assess the condition of the sewer lateral line.  Buyers had to go on symptomatic comments in the disclosure documents – i.e., of the previous owner disclosed that they routinely had to have the sewer line snaked out, it was a good indication that there was a problem lurking underground.

But today, plumbers now utilize small video cameras that they can snake through the line and examine the condition of the entire pipe.   Some Peninsula cities, such as Hillsborough, Burlingame, Millbrae, and Pacifica, now require that the sewer lateral of a home must be video-inspected (and in some cases certified) prior to the home changing hands.  I wouldn't be surprised in the next decade if all municipalities on the Peninsula decide to make this inspection mandatory.

At $250-$500 (depending on who you choose), a video inspection of the sewer lateral is relatively inexpensive.   Especially if it uncovers a condition that may cost upwards of $10,000 to fix.

Posted in:


  1. tomas on February 29, 2012 at 5:26 pm

    Chuck, I’m a little confused. San Carlos Public Works has cleaned out my clogged sewer liner from the cleanout plug to the sewer main on many occasions. I always thought that from the house to the cleanout plug was my responsibility. After that, it’s the city’s responsibility. Please clarify.

  2. Chuck Gillooley on March 2, 2012 at 3:20 pm


    I will double-check with Public Works, but my understanding is that if they suspect the blockage is close to (or beyond) the point where your sewer line meets the city system, they will go ahead and clean that section for you. This is especially true if you have a clean-out that’s fairly close to the street. My neighbor has a clean-out right in the middle of his driveway, which is only about 12 feet from the city sewer line and the city has cleaned that section out for him as well.

    Bear in mind that the City won’t repair any of that section of pipe for free — that’s the homeowner’s responsibility, and hence the impetus behind this post.

    Thanks for your comment.

  3. JG on March 5, 2012 at 6:21 pm

    Hi Chuck,
    In addition to knowing the condition of the lateral, it should also be noted that there are some homes still around without a servicable cleanout for the city. This could add unexpected costs to future remodels as the city has made inspection of the lateral and installation of a cleanout required when making certain improvements. The city has a lot of information online, for example here is the form that details the lateral video inspection.

    Something to think about for buyers looking at properties that look like candidates for adding on master bedroom and bath.

  4. Chuck Gillooley on March 5, 2012 at 6:58 pm


    Great info — thanks for providing that link.

  5. Brad Grayson on March 5, 2012 at 11:51 pm

    Your article is great advice, but comes three years too late for me. The week after I moved into my new house in San Carlos I was leaving for work when I noticed liquid coming from my garage. Upon opening the door I found all of my moving boxes covered in sewage. Everything had backed up through a cleanout drain meant for the washing machine. It turned out that is was due to a deteriorated pipe in the driveway which had become filled and blocked with tree roots. NOT a good experience. A $250 inspection could have saved me the whole experience.

Leave a Comment