Overflow pipes often go completely unnoticed, so much so that many people don't even know what they are. But these pipes serve an important purpose, and if you've noticed that sewage is coming out of yours, then you undoubtedly have a plumbing problem on your hands. Here's what's going on and what you can do about it.
If there's sewage coming out of your overflow pipe, it means one thing and one thing only: you have a blockage somewhere between your house and the sewer. This means that the blockage is likely inside your sewer line that carries waste from your home to the sewer directly.
When a blockage forms in the sewer line, anything that you flush down the toilet or run down the sink has nowhere to go. After enough water and waste fills the sewer line pipe, any more that gets sent down encounters a wall in its way that it can't get through, while a bunch of pressure is still behind it. As a result, it goes one of two places — either back up into your house, with sewage coming out of the tub for an example, or out through the overflow pipe in your yard.
If it's coming out of your overflow pipe, then you should make an effort to stop using the plumbing in your home as soon as possible. There's nowhere for anything to go, so you need to get help before you continue using the plumbing.
In this situation the best thing you can do is to call a plumber. It's not a problem you're going to be able to fix with a drain cleaner or plunger. Your plumber will need to locate the blockage in the sewer line by using a camera and then will have to clear it by using specialized equipment, like a plumbing snake or a hydro jet. Either one will break up the clog and flush it down through the sewer line, out into the sewer, where it shouldn't cause any more issues for you.
Your plumber may also be able to provide some insight on what the clog was made up of. Many people end up discovering that the clog was due to flushable products like baby wipes and tampons that didn't agree with their plumbing. If this turns out to be the case for you, consider throwing these items away instead of flushing them to keep this problem from happening again in the future.