Sewer Line Inspections

A home’s sewer line is something that homeowners and homebuyers never ever think about, yet a blockage can spell disaster. This underground pipe connects your home’s toilets, sinks, bathtubs/showers, etc. to the utility’s sewer pipe under the street or to an onsite septic system. In most cases, it relies only on gravity so it must be installed with a slight downward pitch away from your home. In some cases, an underground grinder pump in your yard helps the sewage reach the sewer system in the street.

The older the home, the increased possibility of hidden damage or blockage to this underground pipe. Tree roots sometimes will grow into underground sewer pipes which can lead to partial or complete blockage. It would be rare that a homeowner would ever have an inkling that their sewer line is partially blocked until they notice that the home’s sinks, toilets, and bathtubs begin to exhibit slow draining. Few homes nowadays have basement floor drains connected to the sewer line. A slow drain at a single fixture likely indicates a partial clog at a specific fixture yet multiple slow draining fixtures indicate a bigger issue. Seeing an area of bright green grass in your yard when the rest of your lawn is dry and burnt out in the summer is a good sign of potential sewer line damage as well.

Sewer pipes are an out-of-sight, out-of-mind thing for most homeowners and home buyers. Most home buyers never even think of having the sewer line inspected as part of their home inspection and some may not even know this service is available. In many cases, sewer pipe damage or blockage can be quite expensive to repair since it often entails excavating the yard to access and replace part (or all) of the sewer pipe. Just to get a crew onsite and start digging to address underground sewer pipe issues often starts at $2,000 and goes up quickly from there.

When I inspected homes, I always recommended my clients consider having the underground sewer line inspected before closing, especially if the home is more than 10 years old. Cast iron and clay pipes were used in older sewer lines; cast iron was still often used into the 1970s in many areas. In some cases, you may only see PVC drain pipe inside your home, yet cast iron may still exist underground out of view. Most modern homes have plastic (PVC) sewer lines underground.

Inspectors use a sewer camera with a long cable and an LED light on the end. As the camera is pushed down the drain pipe, video is recorded to document what’s inside. I’ve seen pipe breakages and blockages from tree roots as well as low spots in the sewer line where water accumulates preventing proper drainage. Sometimes, these low spots are due to heavy traffic on the ground above the line. The underground sewer line is entered either from an exterior (often in the front yard) or interior cleanout (often in the basement) although, in some rare cases, the roof mounted plumbing stack vent may be used. Plumbing standards require that a cleanout exist, at least, every 100′ of sewer line. Sewer line inspections are also sometimes called sewerscans or sewer scopes.

Nearly all homes have a whole house trap installed. In some older homes, this may be within the basement. In colder climates, it may be below the basement floor. For most modern homes, this is generally outside the home in the front yard. You’ll often see two short PVC pipes sticking out of the ground, often near the home. One pipe is a cleanout and the other is a vent. In the above photo, you’ll see a whole house trap installed in a home being constructed. Notice the green lateral pipe coming from inside the basement then entering the whole house trap. The first vertical pipe (left) is a vent. The second pipe with the angle (right) is the cleanout. Both of these vertical pipes run parallel to each other to the surface. The vent has a domed cover but should not be air-tight; the cleanout should have an air-tight screwed on cap. The angle in the cleanout pipe makes it easier to get a sewer camera down into the pipe and directs the camera outwards away from the home in the direction that sewage runs.

Even if there are no trees presently in your yard currently, it doesn’t mean there may not still be underground roots hidden from view. Even when a tree is taken down, its root structure is still in the ground partially alive and still branching out in search of water unseen above ground. Roots can sense water in a sewer pipe and can exhibit an unbelievable amount of force to push its way into a sewer pipe to reach that water, especially at pipe seams or breakages. So a tree that was taken down 20 years ago could still have the possibility of its tree roots clogging the sewer line.

Most homeowners are under the erroneous belief that the public sewer utility is responsible from their underground sewer line. This is not true… homeowners are responsible for the underground sewer line from their home all the way out to the sewer utility’s street connection. A public sewer connection is made up of 2 parts: the upper and lower laterals. The upper lateral is the portion of the sewer pipe that runs between your home and the property line. The lower lateral is the portion of the sewer pipe between your properly line and the public sewer line’s connection often below the street. As noted above, homeowners are responsible for their entire sewer line.

Comparison between a clean sewer pipe and one that has considerable debris accumulation inside of it.

The above photo shows a damaged underground sewer pipe that I inspected several years ago. Part of the top piece of pipe had broken apart and was laying inside the pipe which left the top part of the pipe open to the ground above it.

Sewer line inspections should be done with septic systems, too. Quite often, a septic inspection does not include inspection of the lateral drain pipe between the home and the septic tank but includes the tank and drain field only. What you don’t know about your underground sewer pipe can hurt you in terms of an expensive repair. In some cases, a blocked sewer pipe can also allow a backup into your home where appliances and stored items in your basement could get damaged by water, sewage, and mold. Not something you ever want to come home to.

The inspection of underground plumbing (including your sewer drain line) is well outside the scope of a home inspection as defined by the Standard of Practice of ASHI (American Society of Home Inspectors). Luckily, some home inspectors and plumbers can perform a visual inspection of your underground sewer line to determine its interior condition. A sewer line inspection generally costs less than $350. A wise investment if you ask me. If your home is close to the street, this cost may be a bit lower whereas if there is a considerable distance between your home and the street, this cost may be higher. Having knowledge now can prevent headaches and large expenses later.

Chapter 30 of the International Residential Code (IRC) covers sewer pipes.

Matthew Steger is a retired Certified Level 1 Infrared Thermographer and retired ASHI Certified Inspector (ACI), and an electrical engineer. He can be reached at matthew@thehomeinspectorsnotebook.com. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.