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  • Writer's pictureCameron Home Inspections

Sewer System: Out of Sight and Out of Mind...

Updated: Aug 29, 2022

...until it's not.

If you've ever been unlucky enough to experience a sewage backup into your home or find the smelly mess bubbling out of the ground in your yard, then you know just how destructive and disgusting the problem can be. Major losses to finished spaces, furniture, and belongings can occur with sewage back up...not to mention the sanitary concerns and clean up expenses associated. That doesn't even begin to scratch the surface of how expensive sewer pipe repairs can be. According to Home Advisor, the average cost to repair a sewer line is about $2,500...full replacements can cost upwards of $30,000! We'll get more into that later, as well as some common reasons for sewer problems. We'll also discuss how a sewer system is tested during a standard home inspection, as well as the homeowner's responsibility when it comes to sewer repairs.

sewage back up into bathtub
Sewage back up into bathtub...gross.

But first, let's talk about what a sewer system is. gets rinsed down drains and flushed down toilets all has to go somewhere, and the pipe which allows that to happen is your sewer system.

Each of your house's plumbing fixtures (sinks, bathtubs/showers, toilets) all drain waste water - either to a public sewer main or a private septic system. The sewer pipe, (which usually originates in your basement or crawlspace) that carries waste underground and away from your house is called a lateral. In a public sewer system, this lateral slopes downhill until it joins a larger sewer main, usually under the sidewalk or street in front of your home. Waste is then carried away to a treatment facility where it properly disposed of.

Public sewer system

In a private sewer system, the same lateral applies, except this time waste is carried to a septic tank. In the tank, the waste separates and breaks down. Eventually, this separated material called effluent flows to a distribution box that then sends the waste out into a drain field. Here, it is safely absorbed in the soil.

septic system, sewer lateral, inspection
Private sewer system (septic)

Sewer pipes come in various sizes and materials. They're usually three or four inches in diameter and are constructed of PVC (polyvinyl chloride), ABS (acrylonitrile butadiene styrene), cast iron, or clay. Some other materials exist - most notably a product called Orangeburg that was used into the early 1970s, but this type of pipe is no longer produced or installed due to its tendency to collapse and fail prematurely.

Newer homes typically have plastic sewer pipes (PVC, ABS, or a combination of both). These materials are strong, lightweight, readily available, corrosion resistant, relatively inexpensive, and easy to install. Each have their own pros and cons, but for the most part, they're the standard for today's sewer pipe installation. A sewer system like this, especially a newer one shouldn't have any issues, but can certainly be affected by a number of factors we will discuss in this article.

PVC installation in new construction

Cast iron pipes are very common, especially in older homes. This material can last many decades in ideal conditions, but like any ferrous metal, cast iron is vulnerable to corrosion and usually fails from the inside. A condition called scaling occurs when the inner surface of the pipe becomes coated with a layer of rust and mineral deposits. Since scaling creates an uneven, rough surface, solid waste can become lodged in the pipe which eventually leads to clogging and backups. Descaling methods such as hydro jetting allow a contractor to spray a high pressure stream of water inside the pipe which is powerful enough to remove the build up. This can, however, damage the pipe if it is already degraded too much.

Scaling, cast iron pipe, sewer inspection
Scaling in cast iron sewer lateral

Clay pipes are some of the longest-used materials available and are often encountered during sewer scope inspections. In fact, the use of clay pipes for sewage disposal can be traced back to ancient Babylonia (4000 BC)! Clay is very strong and does not corrode like cast iron, but it is particularly susceptible to joint separation from settling or root intrusion. When a joint in a pipe is no longer aligned, an offset is formed. This creates a lip where solid waste can get stuck. Continued build up on the offset can lead to clogging and back ups.

offset, plumbing inspection, sewer scope
Offset with debris stuck on bottom and root intrusion

Another common problem I see in all kinds of sewer pipes is the presence of roots. The waste that flows down sewers is nutrient-rich for plants, so their roots will naturally grow toward that source. Those pretty trees and shrubs that give our homes great curb appeal can have catastrophic effects on sewer pipes - here is a photo that shows just that:

75% blockage from root intrusion

A method called snaking can be employed by a plumber or even as a DIY project with a rented machine to remove roots from inside a pipe. I ran across this video that shows the process and results - but keep in mind, the roots found their way in the pipe somehow, meaning a hole, crack, or offset allowed entry. Even though snaking takes care of the immediate problem for now, the underlying issue is still present...and you can bet the roots will return in time.

Roots in PVC sewer pipe
Even PVC is no match for aggressive roots

A belly, or sagging area, in a pipe is another common find. As the ground naturally shifts over the years (or if a sewer was improperly installed), these low spots will occur...even in newer homes. We all know that stuff flows downhill, but if a portion of that downward sloping pipe has a sag, solid waste will tend to pile up which can lead to clogging.

belly in pipe, sewer inspection
Belly with standing waste water

Now that we've defined a sewer system, discussed some of the more common materials they're constructed of, and explored a handful of issues I see on a regular basis, let's shift gears to the actual home inspection. Nearly all Inspectors will perform some variation of what is called a functional flow test to analyze how...well...functional your plumbing system appears to be working. Since a home inspection is typically limited to what the Inspector can visually see with his or her own two eyes (much more detail on that can be found here), there is no way to know with any degree of certainty how the inside of that sewer pipe actually looks. The test performed often includes turning on water at multiple fixtures while simultaneously flushing a toilet.

functional flow test during home inspection
Functional flow test; out of frame, bath faucet is running

The functional flow test can certainly be an indicator of problems - for instance, a severely clogged sewer can indicate itself by how slowly a sink or bathtub drains. That said, I have seen too many houses "pass" their functional flow test yet still have significant sewer defects. The photo I showed earlier with the pipe nearly full of tree passed the flow test! Have a look at this sewer inspection video from one of my recent inspections - two occupants lived in the home and regularly used bathrooms, sinks, and the dishwasher (this information will be important in just a bit). In about 50 feet of sewer lateral, you will see multiple bellies and offsets (one with roots beginning to grow in from the top), considerable scaling, and a huge crack in the cast iron. Want to take a guess at the results from its flow test? Pass. While the functional flow test can certainly indicate problems, there is no substitute for getting eyes on with a sewer scope camera inspection.

broken sewer pipe, sewer inspection, cast iron lateral
Severely cracked cast iron sewer pipe

Another consideration is to analyze how much use a sewer system is actually getting on a daily basis. Let's assume for the sake of example that your young family has grown to six members and you are looking to move into a larger home with a little more elbow room (and another bathroom)! You find the perfect home that an older couple is selling - they want to downsize now that their own children are grown and have moved away. The sellers had taken great care of their home, but the sewer system hadn't been touched in decades. And why should it? No concerns had ever been raised when they had a full house and it worked just fine for the two of them ever since. Now imagine purchasing that house, moving in, and immediately throwing a 75%+ increase in waste water down the sewer system on a daily basis. We've seen how mostly-blocked sewer pipes can still handle a functional flow test, and we've seen how damaged systems appear to work just fine under regular usage by a couple occupants...but that doesn't come close to replicating the demand placed on the system from our example.

To recap on the components of both public and private sewer systems...the pipe usually is accessed from the basement or crawlspace of your home, and the pipe will exit the foundation wall or travel under the house's slab on its way down to either a septic tank or the sewer main. Septic systems are typically found in more rural areas without a developed public sewer main system available, and each component is almost always the homeowner's responsibility. For public sewer systems, the lateral often travels under the homeowner's front yard, under the sidewalk, verge, and curb, and connects to the sewer main under the street.

public sewer lateral diagram
Public sewer lateral

The properly line, as depicted above, separates the upper lateral from the lower lateral. A common assumption is that the property line separates repair responsibilities - anything on the house side of the line is the homeowner's responsibility, and anything on the street side of that same line falls under the city's (or sewer utility company's) ownership...however, this can vary among different municipalities. Sometimes, the property owner is responsible for the entire lateral, all the way to the city main connection. Other times, the property line does in fact divide responsibility...however, if a condition located on the homeowner's property causes damage to the lower lateral, the property owner may be liable for repairs. A great example of this would be a mature tree in a homeowner's front yard. Large trees have powerful roots that can stretch far, wide, and deep - you've probably seen instances where tree roots even uplift and crack concrete sidewalks! If one of these roots stretches across the property line and damages the lower later, the homeowner will likely be held responsible.

tree root, broken pipe, plumbing, sewer inspection
The tree root crushed this section of pipe

As you can probably guess, sewer repair costs can skyrocket quite quickly. In my area of St Louis, even a basic sewer lateral repair costs around $2,000-$3,000 (I've discussed with a number of local plumbers to reach that conclusion). As problems become more complex, the cost of both labor and materials will increase - imagine if the issue is located under your home's concrete slab in the basement. Accessing that can only be done through destructive measures - it's loud, messy, time consuming, and expensive.

sewer repair in basedment
Concrete demolition is often required for repairs

Now imagine having to replace an entire sewer lateral...since waste has to flow downhill, the pipe gets progressively deeper on it's way to the main line - we're not talking a weekend project with shovels...this job will require heavy machinery. Excavators or backhoes will be needed to access the line which can be buried 6 feet deep or more. Does the lateral pass under dirt only? Is a concrete or asphalt driveway over top? You see where this is going...

Sewer lateral repair in the mud
Large, muddy repair

Here's another hypothetical... and the worst case scenario. Imagine the sewer line problem is located near the city main - under the sidewalk and street. The municipality sends their own Inspector, and they identified the cause as roots from your mature tree in your front yard. The lower lateral needs extensive repairs, and just to access the problem, both the sidewalk and a portion of the street will need excavated. The city's Public Works Department has to be involved...and since your tree caused the issue, you get the bill. While this scenario is not overly common, it is not unheard of. Prior to purchasing a house, I strongly recommend a sewer lateral inspection as well as researching where repair responsibly stands, especially at the property line.

Major sewer repair, sewer inspection
Major sewer repair

If for nothing more than peace of mind, I recommend a sewer lateral camera inspection to each of my clients...this even includes homes only a few years old, but as soon as the homes reach 20 or more years of age, the likelihood of problems increases drastically with ground settling, roots, and corrosion. Trees or shrubs planted over the sewer line are big red flags - remember, that pipe may only be a foot or so deep where it first exits the home's foundation and plant roots can cause significant damage much deeper than that. If your sewer is in good working condition with no major issues, that's great! You confidently know the details based on your inspection video and images. If we find problems, your sewer inspection could save you thousands of dollars in repairs prior to closing.

4 year old (young!) PVC lateral with early root intrusion

I hope this article has helped shed some light on the different types of sewer systems and what they're constructed of, a few common issues I see regularly, the limitations of the standard functional flow test during a home inspection, and just how expensive sewer repairs can be. If you found the information above useful, please share it with a friend and as always, call, text, or email at any time with questions or to schedule your sewer scope inspection!

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*The views and opinions expressed in this blog are those of the author and do not necessarily reflect the official policy or position of any other agency, organization, employer or company.

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