Where is the sewer line in a house?

Author: Collin Hayes DVM  |  Last update: Wednesday, January 28, 2026

It can typically be found in the basement, crawl space or garage. You will want to search for a pipe that is approximately four inches in diameter with a screw cap on the top that has a notch or square knob at the top. Note that some homes have an indoor sewer cleanout point, while others may be located outdoors.

How to find main sewer line in house?

Your home's sewer cleanout is a crucial part of your plumbing system. You'll usually find it outside, about 1 to 3 feet from where your house meets the ground. Look for a pipe sticking up with a cap on top that might have a square knob or notch for turning.

Where is the drain pipe in a house located?

Main drains are located in the walls and floors of your home, while sewer line drains are located outside underground. Each drain pipe in your home is connected to a different household fixture on one end, including toilets, sinks and bathtubs, and the other end is connected to the main sewer line.

Where do sewer lines usually run?

A house sewer runs underground from the street to the house. Typically your main drain pipe is either 4″ or 6″ inches in diameter. The house drain inside your home is connected to your house sewer pipe at the front wall of your building.

What does a main sewer line look like?

You may spot a 3 to 4-inch diameter pipe peeking out of the slab floor of the basement. The sewer drain pipe could be made of plastic or cast iron; it might be copper or brass in rare cases. The stub-out will have a screw-in plug coupled with a square-head lug on it, representing your access to the main drain.

How Your Home Plumbing Works (From Start to Finish) | GOT2LEARN

How do I know if my sewer line is clogged?

10 Signs Your Sewer Line Is Clogged
  1. Multiple Fixtures Are Clogged. ...
  2. Flushing the Toilet Causes Water to Come Up Elsewhere. ...
  3. Water Draining From Your Washing Machine Causes an Overflow in Other Locations. ...
  4. Drainage at the Cleanout. ...
  5. Slow-Draining Sinks or Toilets. ...
  6. Frequent Plunging. ...
  7. Bubbles in Your Toilet Water. ...
  8. Dark Water.

How far down is a main sewer line?

The main sewer pipes run right down the middle of the roadway. They're normally about ten feet below the surface, although they might be a lot deeper. Once you know the depth and location of the main sewer, you can calculate the slope required for your sewage to flow freely through the pipe and into the main sewer.

How much does it cost to fix a clogged sewer line?

You will likely pay around $350 to $650 to have a plumber unclog a main sewer line unless you have complications like serious damage to the line.

How many sewer lines does a house have?

Not in most homes. Ordinarily, you have one sewer line that is intended to primarily carry what's known as “black” water; water from the toilets into either the city sanitary sewer system or into your own septic tank.

How to find out if property has a sewer?

contact your town or city they have maps of the sewer lines. They will also tell you where the citys responsibility ends for the sewer line. most times it is at the property line.

How to unclog main sewer line?

Your step-by-step guide: How to clear a main sewer line clog
  1. Step 1: Loosen the cap on the drain pipe. ...
  2. Step 2: Open the cap and let the buildup drain out. ...
  3. Step 3: Feed the auger cable into the drain pipe. ...
  4. Step 4: Run the auger until the clog is clear—and beyond. ...
  5. Step 5: Hose down the pipe and auger cable.

Where is the waste pipe in my house?

All wastewater from your house is carried to the municipal sewer line by one main drain pipe that typically runs horizontally, but with a slight downward slope, under the lowest floor in your home out to the municipal sewer main or out to the septic field.

How many sewer cleanouts does a house have?

Many homes have two clean-outs (see below). One is near the foundation of the house and the second is at or near the property line. First, check the clean-out next to the house to see if it has water in it. If it doesn't contain any water, then you know the blockage is somewhere in the house plumbing.

Is the main line the same as sewer line?

Simply put, your mainline is your sewer line. And all your drains connect to your main line. Your main line is also the line that goes from your house to the city connection or your septic tank. Before leaving your home, all of your drains dump into your mainline.

Does the main sewer line always have water in it?

The second answer is NO: If you notice that drains are overflowing or making a gurgling noise or even sucking the water seal dry it would most likely point towards a fault in the drainage system.

How to locate drainage pipes?

Use a Wire Tracer or Utility Locator: This is a device designed to locate underground wires and pipes. While some models are designed for professional use and can be quite expensive, there are simpler models that may be adequate for smaller tasks.

Where are the sewer lines on my property?

Most of the time, the sewer line will be sticking out of the ground and easy to spot; however, overgrown landscaping or objects close to the house could hide the cap. Or, you could have a buried sewer cleanout. Try searching on the side of the home that is closest to the main floor bathroom.

What is the difference between a sewer line and a drain line?

The main sewer line is outside the home, while drain lines are inside your house. When these systems need maintenance or repairs, the type of plumber you should call will depend on whether the problem is in a drain line inside your home or the main sewer line outside your home.

How deep are most sewer lines buried?

Residential sewer line pipe depths range from as shallow as 18 to 30 inches in depth or 5 to 6 feet deep. However, in colder climates where freezes occur, you often see sewer line depths ranging from 4 to 8 feet deep. This ensures the pipes are below the freeze line.

Does homeowners insurance cover sewer lines?

In most cases, home insurance will cover sewer line damage from specific events. This includes extreme weather (excluding earthquakes and floods), vandalism, fire, and damage from vehicles or falling objects.

How do you tell if a sewer line is clogged or broken?

Strange Smells and Noises

Foul smells emanating from your sink, bathtub or floor drain indicate a main sewer line blockage. The clog leaves nowhere else for the waste causing the smell to go, leaving a lingering odor. In addition to strange smells, you might also notice a gurgling noise coming from your drains.

How many years does a sewer line last?

Generally speaking, you're going to find that most main sewer lines will only last somewhere between 50 and 100 years before you need to do a main sewer line replacement. You could very well have a broken sewer line on your hands right now and not even realize it.

How do I know where my sewer line runs?

Dial 811

Probably the most convenient method, you can dial 811 in the United States. This national hotline connects you to your local utility company, allowing you to request that utility professionals come to your property and mark the location of various underground utilities, including your sewer lines.

How big is the sewer line from house to street?

Depending on your local plumbing codes, the main sewer line for residential homes is usually 4 inches in diameter. You may think if the pipe were larger, more waste could travel without getting clogged.

How deep is a sewer cleanout?

The sewer cleanout is capped off with a cleanout cap where the pipe is open above ground. Whether your sewer line is 8' deep or 3' deep it doesn't matter. The section of pipe that is extending the sewer opening above ground will give access to your sewer line without having to dig up your sewer line.

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