Main Sewer Line Clogs: Causes and How to Fix Them

Home / Main Sewer Line Clogs: Causes and How to Fix Them


If you find yourself with a slow drain or even a total backup and have come to the internet to figure it out, it’s possible you’ve come across the term “Main Sewer Line” at some point in your research.

But what is a main sewer line and could that be causing your drainage problem?

While it’s not the cause of your problem, it could be where your problem lies.

What Is the Sewer Main Line?

You wash your hands, flush the toilet, and run your washing machine. But what happens after that? Where does the wastewater go?

The main sewer line? Eventually, yes.

You see, your home’s sewer system is made up of various parts.

There are the parts you see like bathroom and kitchen fixtures and depending on your home, the pipes under your sink leading from the fixtures then underground.

While every home is different, there are typically the same parts. Think of your sewer system like a tree. Wastewater drains into different branch lines like branches on a tree. Each branch line could have a few different places water drains from.

For instance, in many homes the kitchen sink and the washing machine are on the same branch line. Also your bathroom sink and shower are also probably draining into their own branch line. Each branch line is connected to and drains into your main line like the trunk of a tree.

Then the main line leads out of your home and feeds into the city line which starts at the street or alley.

Can the Main Line Get Clogged?

In short, yes.

In point of fact, every line can get clogged from the pipes directly under the fixtures to the branches and main line and even the city’s lines.

If water and debris is running through it, it can get clogged. Toilet paper, food waste, oils and soap scum, hair, all these and more can build up and cause a blockage in your system.

There are also other things can cause a clog like tree and shrub roots. But those are possibly signs of another problem, a hole or break in your sewer line. Tree and shrub roots don’t cause holes or breaks in your line, but they are attracted to the water that leaks out of the existing holes.

If you have a clog in the main line, it’s likely affecting all of your plumbing fixtures since every branch in the house feeds into the main line. Whereas if it’s just affecting one or two like the bathroom sink and shower but not the kitchen, then the clog is probably not in the main line but in the branch line.

Can I Unclog the Sewer Main Myself?

While it is tempting, I cannot stress enough that you do not use chemical drain cleaners to try and fix the problem yourself.

The chemicals in products like Drano or Liquid Plumber can damage your pipes and sometimes even make the problem worse. Depending on what’s causing your clog, these grocery store products can’t get through them and instead pile up creating an even bigger clog. And then instead of draining through your system, those chemicals are now sitting there eating away at your pipe’s lining.

So what should you do instead?

How to Clear a Sewer Main Line

You have a few options here, with some that allow unclogging without a snake.

Blow Bag

You can get a blow bag at a home improvement store or order one online. Attach the blow bag to a hose and feed it into the drain until it stops. You want to get the hose into the line as far as possible but don’t force it.

Once you turn the water on, the bag fills with water and then bursts out hopefully creating enough pressure to clear whatever is clogging your pipe.

Sewer Machine

Another option is a sewer machine. These are also called sewer snakes, plumber’s snake, drain snake or variations of all of those. You can rent one from a home improvement store or even buy one.

You feed a cable that is attached to the machine into the pipe. Just like with the blow bag hose, you want to keep pushing it in but don’t force it. Once the cable hits the obstruction, depending on the type of machine — mechanical or motorized — the attachment at the end of the cable spins breaking up whatever is causing the clog.

Once the clog is broken up, flushing the pipe with water should clear the debris that is left.


There are a lot of things that can go wrong if you don’t know how to or haven’t operated a sewer machine. This is why I don’t recommend the layman homeowner use one of these machines.

You could damage your pipes, the machine not to mention also hurt yourself if you don’t know what your doing.

Call a Reliable and Licensed Plumber

To try both of the options above, you need to find the sewer cleanout. These can be in a number of locations so you just have to look for it. It could be coming out of the ground close to your house or somewhere on the side of the home. And if you don’t have one or can’t find it, you need to call a plumber.

If you’ve exhausted your options and you still have a clog, contact a licensed plumber. We have sewer machines in a variety of sizes not to mention can more accurately diagnose your problem.

Calling a plumber when you can try to DIY it might sound like an unnecessary expense. But imagine how much more you’ll be spending if you cause more damage or hurt yourself.

Cost to Unclog a Main Sewer Line

To say something I’ve said many times here on the blog, it depends. Every house is different so there is no one-size-fits all fix or cost.

Generally speaking, though, it can cost you anywhere from $100 to $250. A lot depends on the company you use and what needs to be done.

Here at In-House Plumbing Company, we find it typically runs around $150 to $175 for us to clear out a main sewer line clog. But again, it depends on your system and the problem.

Every situation is different.

What if the City Sewer Line is Clogged?

If you suspect the clog is not in your home’s system but in the city’s, call the city. Homeowners do not take care of the city’s line. Your responsibility is only what is in and under your home and the line from your house that runs to the alley or the street.

So if you even think it’s possibly the city’s line, call them. This saves you time and money because they will come out and do an investigation. They may tell you it’s on your side and if that’s the case, you can take steps to get your problems solved.

I’ve never seen a city charge for coming out to investigate and find it’s the homeowner and not the city. Sometimes they even clear something if it’s in the yard. Although, they generally don’t do that much anymore because of liability problems, too many sue happy people these days.

Call In-House Plumbing Company

If you think you have a clog in the main sewer line or anywhere in your sewer system, give us a call at 972-494-1750 or email
We can help you determine if you do in fact have a clog and if it’s in the main sewer line. From there we can come up with the best repair option for you and your budget.


In-House Plumbing Company

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