What Causes Sewage Backups?

Are you overpaying for car, home, or renters insurance? Compare to find out in 45 seconds.
Quotes from up to 45 companies · No long forms · No phone calls
Sewer (Photo: @kitzingener via Twenty20)
If Steve Harvey asked “What is the worst thing that can happen to your home?” on Family Feud, sewage backup would definitely be in the top three answers.
A homeowner’s nightmare, a backed-up sewer is not only grotesque, it could also be extremely costly to repair. To ensure you’re not blindsided by your sewer system, here’s a list of the common causes of sewage backup.


If you have an ancient sewer system and you’ve adopted the out of sight (and out of smell) mentality, prepare to be sorry. An old sewer system, gone unmaintained for decades, is a ticking time bomb. To prevent the inevitable, have your sewage system inspected by a professional once every few years (or as needed).

Tree roots

That’s right. Trees may seem like unlikely culprits for such a horrific crime, but they could indeed be at fault. Tree roots grow where they please and sometimes that means twisting through underground pipes and other home systems.
Tree roots can shift pipes, causing sewage water to leak out and end up where it shouldn’t be (namely, your basement). Such incidents do not only result in a smelly mess, but also potential water damage. To prevent your trees from wreaking havoc on the sewage system, consult an arborist before planting new trees.

Heavy rain or flooding

Sewers can also back up if too much water enters the drain pipe (or sewer line) at once. The sewerage system doesn’t have the capacity to contain an infinite amount of liquid, so if it reaches its limit, it will eventually flow back into your home.
To prevent this from happening, install a backwater valve in your septic system. Backwater valves are essentially one-way roads for your septic system, so there’s no turning back.
Also, make sure you have an adequate amount of floor drains in your basement so if the worst happens, at least the sewage will drain when the backup subsides.


A buildup of solid objects in a sewer system is bound to cause blockage eventually. Common culprits include grease, hair, and other random things people shouldn’t be flushing down the toilet. Before you flush, ask yourself “Would my mom get mad at me for flushing this?” If the answer is yes, then don’t do it.
As with many elements of your home, proper maintenance goes a long way. Have a plumber inspect your septic system every year or two, so they can spot issues before they become catastrophes. Likewise, have your septic tank pumped and cleaned regularly so waste doesn’t build up. It can be a costly investment to replace old pipes with new plastic pipes, but if it’s time … it’s time. Trust us, it’s an investment worth making.