Should There Be Standing Water In The Main Sewer Line? (Explained)

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There should be water standing in a certain location of your sewer drains. This prevents smell and rodents from entering the building. But, there shouldn’t be water in some parts of the main sewer line. If you notice standing water in the main sewer line, it’s likely the drainage system is damaged.

Why is water coming out of my sewer line?

For homes connected to a sewage system, the sewer line bridges the gap between the home’s drainage system and the main sewer.

If you notice water coming out of the sewer line, it could be a sign that there is a blockage somewhere. For this reason, there is no free flow of sewage from your home drain to the main sewer.

Another reason water may come out of your sewer line can be because of a break in the sewer line. The sewer line is pipes located under the ground of your yard, where sewage passes.

Disruption in the landscape from the tree root, or manmade can break the line, causing the sewage to leak.

Note, the sewer line is considered part of your plumbing system, and so it is your responsibility to repair and maintain it.

Should there be standing water in the main sewer line?

Yes, there should be standing water in certain parts of your main sewer line like the toilet pan, J trap, and so on.

But if you notice an unusual amount or level of water in the main sewer line, then it could be as a result of a blockage.

Note, several factors can cause standing water in certain locations of the main sewer line where it shouldn’t, namely:

Rodent problem

Rodents can cause standing water in the main sewer line. Rodents like rats live in sewers.

Did you know that an average rat can squeeze itself through a sanitary sewer about ¾ inch wide? They do and can clog the sewer line as well.

Sadly, when the sewer line gets clogged it can cause standing water problems.

Broken or bent sewer

Another reason you might experience a standing water problem is if you have a broken or bent sewer.

A broken or bent sewer can prevent the free flow of sewage into the main. As a result, the water remains stagnant.

Landscape growth

Tree roots can also cause problems in your sewer line. For this reason, homeowners are advised against planting trees too close to the main sewer line.

Roots can cause the sewer line to dislodge, or bend which prevents the free flow of sewage through the line.

Insect infestation

You might least expect it, but an insect infestation can cause standing water in the main sewer line problem.

Insects such as sewer flies, palmetto bugs, and cockroaches can easily get into the sewer line. Insect activities in the sewer line such as breeding, housing, waste, and so on, can quickly build up causing a clog.

Grease build-up

Grease build-up can also be another reason you are experiencing a standing water problem. Grease like fat and grit are the major cause of sewage clog. When fat and grit are poured into the drain, they stick to the wall of the sewer line and eventually solidify over time.

Sanitary paper products

If you are the type to flush sanitary products such as facial tissue, paper towel, feminine hygiene products, and extra-thick toilet paper, you should stop. These products can easily clog your sewer line. And if your sewer line gets clogged, it can cause a standing water problem.

How can you fix the standing water problem in the main sewer line?

A standing water problem in the main sewer line is a problem you can fix yourself. All you need is a hose and snake line, and we’d show you how to go about it in the step-by-step guide below.

Step 1: Find the clean-out fitting

Locate in your home’s plumbing system the clean-out fitting. Most times, the clean-out fitting is a pipe measuring 3, 4, or 6 inches wide. It often sticks out above the ground on the lowest floor of your home, on the level ground outside. The visible section of the clean-out fitting should be able to unscrew with a wrench.

Step 2: Loosen the cover of the clean-out fitting

When you find the clean-out fitting, use a wrench to slowly loosen the cover first. Do not pop it completely open as this can cause the waste build-up to explode out of the opening.

The reason for this is because of pressure buildup in the sewer line. So as you open it, step away from the pipe when you loosen the cap.

Step 3: Allow the buildup to spill out

Once you open the clean-out fitting, step away and let the buildup spill out. Give the sewer all the time it needs for the buildup to spill out completely until nothing spills out of the drain.

Step 4: Feed a plumbing snake in the clean-out fitting

Although letting the buildup spill out will partially unclog the clogged main sewer line, it is not enough to get rid of all the clog.

So, when you notice the buildup has to stop spilling out itself, feed the plumbing snake in to remove as much of the clog as you possibly can.

Note that you may have to use the plumbing snake several times as long as you keep hitting dirt inside the pipe until it is free.

Step 5: Hose down the inside of the drain

While the snake is still in the drain, hose it down with water to push the smaller clogs and leftover debris that the plumbing snake can’t remove into the sewer.

After this, remove the plumbing snake and place the cover back onto the fitting. Test the drain and see if you will still have standing water.

What to do if it’s still not working, or you can’t clear out the standing water

If you still have standing water at this stage, then we recommend you involve a professional. The professional will properly diagnose your sewage system and tell you where the problem resides.

Perhaps you didn’t clear out the clog properly, or you didn’t clear out the right place. The plumber will let you know and fix it for a fee.

If the reason the standing water persists is that something is broken in your sewer line, the plumber will have to replace it. Note that the cost to clear out the main sewer line will be cheaper compared to replacing any section of your sewer line.


In conclusion, standing water in the main sewer line of your home is not always a sign that something is wrong.

Before you conclude your sewer line is broken or faulty, first confirm with friends that have plumbing skills if it is normal to have water in the area of concern. If it is normal, then you are good to go.

But if it isn’t, then you can try out the steps on how to clear the main sewer line we explained in this article.