Quick References

Preventing Sewer System Backup in Grid-Down Scenarios

One of the little-mentioned concerns I’ve had for a while (but haven’t seen often addressed or adequately addressed myself) is this simple question: What will I do in a long-term grid-down scenario to prevent a sewer backup into my house? After all, if there’s anything I don’t need in such a situation… it’s raw sewage to cleanup!The best solution for homeowners is to install a sewer backflow preventer on the main sewer line, which could include installing a sump pump too. In many cases installing a backflow valve was required when the home was built. Contact a local plumber, the city,  or even your home builder to find out for sure. Unfortunately, if one wasn’t installed, the process of installing a backflow preventer can be quite costly and time-consuming. (You can view a YouTube video explanation of the process at the end of this post.)

But what can you do if you don’t want that hassle or expense? There are two other methods that I’m aware of: one VERY permanent and one temporary.

The VERY Permanent Solution (and NOT recommended solution)

Use a bag of fast-curing concrete mix, such as QuikCrete, to permanently seal off your main sewer line. Basically, you’re plugging your sewer line with concrete. Please understand this is NOT recommended unless there is absolutely no possibility of returning to normal life! (Note: I was hesitant to even mention this idea because I’m sure somebody will try it someday. I’m just including it to be thorough.)

The Better, Temporary Solution

Use a sewer test plug to stop your main sewer line. This is without a doubt the better option. To use this device you’ll have to locate the main sewer clean-out and be able to pump up the test plug. You’ll also want to know the size of your sewer drains (usually 3″ in diameter) in order to purchase the proper size plug. Visit a local plumber’s supply store (probably not your local hardware store) to get one or you can see what a test plug looks like. You might also read this PDF on How to Plug Your Sewer Line with a test plug.

Another Idea I Found

I can’t remember from whom I saw this idea (it was in a YouTube video for sure), but this lady suggested using something like a racquetball or handball ball that can be inserted into a drain. Unfortunately, the diameter of a racquetball ball is a little over 2 inches, while the diameter of a handball ball is just under 2 inches, which means they are not large enough to stop a main sewer drain.

They may, however, fit inside a common shower drain, sink drain, or toilet drain (diameters are usually 2 inches but can be 1.5 inches). So, this could prove useful to limit sewer backup to individual locations. If I had to choose between a racquetball ball or handball ball, I would go with the racquetball ball because it should stop up to 2 inch drains as well as be flexible enough to fit into small drain diameters. Of course, the handball ball is harder and probably more likely to resist than a racquetball ball.


Obviously, whatever you choose to do will require that you and your family understand that ALL of your drains, sinks, toilets, and so on cannot be used until the drains have been returned to normal. So, remember to seal off all your drains so others know not to use them. A simple length of tape could be used to seal toilet seats down, tape shower doors shut, and even to block access to sinks as though they were crime scenes. What are your thoughts?

Installing a Backflow Preventer


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