What is a Lateral?

Your sanitary sewer lateral is the pipe that carries your wastewater from your home (toilets, sinks, showers, laundry, floor drains, etc.) to the public sanitary sewer main that is typically in the street.

Just like roofs and driveways, maintaining a lateral is the homeowners' responsibility. Some communities require homeowners to repair and maintain laterals from the house out to around the sidewalk or tree lawn, what's known as the right of way. In other communities, homeowners own the lateral from the house all the way to where it connects to the city's sewer system in the street. Check with your city to find out.

MMSD has financial incentives available to homeowners to replace their sewer lateral. Visit the Pipe Check Program to learn more!

illustration of a how a lateral works with your home

Laterals are only supposed to carry the water you use in your house out to the city's sanitary sewer pipe. Cracks and leaks in laterals end up allowing groundwater into the sewer, which can overwhelm the overall system and cause stormwater and wastewater to back up in the sewer system and into people's basements.

If it's not raining and you get water backing up into your basement through the floor drain, there's a good chance you have a clogged lateral. The water that you used inside your home cannot get through the lateral and empty into the city's sewer out in the street.

Even if it is raining and you have water coming through the floor drain, you could still have a clogged lateral that needs to be cleaned out. When basement backups occur because the public sanitary sewer system is full, typically your neighbors will have the same problem at the same time. Contact your city or village department of public works right away so they can check to see if there are any problems with the public sewer in the street.

If you have ever had to call a plumber to unclog your lateral, you most likely have a damaged and leaky lateral. Tree roots are always seeking water and end up growing through cracks in laterals. The roots end up catching things that are flushed or poured down the drains in your home, leading to a clogged pipe. You can tell when your lateral is clogged when water backs up into your basement through a floor drain, sink, toilet or other plumbing fixture during dry weather or wet weather. In dry weather, the water that is backing up is water you used in the home that cannot get out the lateral to the city's sanitary sewer in the street. During wet weather, water leaking into the lateral can start backing up into the basement since it can’t run out fast enough due to the blockage.

If you suspect problems with your lateral or you would just like the peace of mind, you can check for blockages, leaks, and cracks by having a plumbing company run a television camera through your lateral. You will be able to see any major problems right away. When your municipality looks for widespread problems in the sewer and laterals, they often use an environmentally friendly green dye to soak into the ground. When the camera views green water in the lateral, they know there are leaks in the pipe.

If you get a lateral inspection, make sure to get a copy of the video. You may want to get a second opinion on any problems that are diagnosed and potential solutions.

Sanitary Sewer Lateral Basics

How to Locate Your Lateral 

Follow these steps to locate your lateral.

Your lateral starts where your house sanitary plumbing goes vertically into the basement or crawl space floor from the upper levels of the house. This large pipe is usually about 4” in diameter and made of cast iron or plastic and often referred to as the sanitary stack. There is usually a branch from the pipe with a cap for access which is called the cleanout. Often the sanitary stack is located near the water service line and water meter. While not recommended, if your basement is finished, the sanitary stack is often covered by a wall or panel.

locating your lateral in your basement

Locating your lateral in your house example.

Once you locate your sanitary stack inside the house, make a general reference from the location inside the house to a spot you can identify outside the house. You can do this by using a tape measure to measure the distance from the nearest corner or window of the basement and transfer this measurement outside the house. Once outside the house, use your reference point and measurement to estimate the location of the sanitary stack inside the house and look straight towards the street. This typically is the location of the lateral across your yard. This is only approximate. If any digging is planned by you or others in your yard, you need to have all utilities professionally located by contacting Digger’s Hotline.

How to Acess Your Lateral

Typically, your home will have three (3) access locations:

This is located on the sanitary stack or cast into the basement floor.

To locate an interior clean out, start in the basement along the wall closest to the street. If the property is located on a corner or intersection, there could be more than one exterior wall nearest the street. Material: clean outs could be cast iron or PVC and are usually located on the floor near an exterior wall. However, they could also be on or near a wall, inside a wall, inside a cabinet or located on the main plumbing stack. The clean out could be located near the water meter (where the water service line enters the home). Typically, these services enter the home in the same area.

Not common in our area unless you have a long sanitary lateral (over 100’ from the street sewer to your house). If your sanitary lateral has been replaced or had repairs in the past, you likely do have an exterior cleanout.

Some properties also have one or more cleanouts outside their home, which allows additional access points to the lateral. If you know the path of the lateral exiting your home, look along that path, the cleanout would be somewhere between the home and where the lateral connects to the sewer main under the street. 

Tip: If the clean out cap is broken or missing, this is a repair you will want to get addressed as soon as possible. An open access point could risk damages, or blockages to the lateral. Lateral damage or blockages can increase your risk for costly repairs or basement back ups.

The floor drain is a plumbing fixture in your basement floor that accepts standing water near or around the drain. The floor drain is another access point to your lateral. The lateral should only be accessed by a professional plumber. The sanitary lateral is a direct connection to the public sewer including the gases, odors, and other undesirable elements that come to mind. Your house is protected from these elements with water traps on all plumbing fixtures. Accessing the lateral bypasses this feature and leaves an open pathway for gas, odors, etc. into your house. If you smell sewer gas in your house, the most likely source is a water trap that has dried out from non-use. Floor drains are particularly prone to this. Pour at least one gallon of water in all plumbing fixtures including toilets and floor drains. If odors persist, contact a plumber.

If you are not able to locate the clean out, try some places it could be hidden or covered up. A clean out could be located inside a cabinet or closet, under a table or bar, or it could also be under carpeting or other flooring if it was covered up.

photo of cleaning interior lateral pipe
photo of cleaning exterior lateral pipe
photo of basement floor drain

How Should I Maintain My Lateral?

If you need to have a contractor clean and cut roots out of your lateral on a regular basis, you should have your lateral video inspected every five to ten years. If you have never seen the inside of your lateral, having a video inspection is relatively inexpensive peace of mind. If the lateral is in good condition, there is no need to re-inspect for the foreseeable future. New laterals are made out of PVC, a high-strength plastic that is slightly flexible. PVC pipes for home laterals are typically in10-foot segments and have long-lasting, water-tight joints when installed properly. Plumbers started installing PVC laterals in Wisconsin in the 1970s.

Older laterals may be made out of clay pipes that were typically installed in two-foot sections with joints that either are not sealed or have seals that failed long ago. Clay pipe material is extremely durable over time, however, the pipes are susceptible to cracks and damage that lead to failure over time. Tree roots are the most common cause of damage.

  • "Flushable" wipes, feminine hygiene products, cat litter, or other materials that do not easily break down or that can clump and clog your lateral.
  • Never pour or flush hard chemicals, paint, oil, pesticides, cement, plaster, medications, or more than the recommended amount of drain cleaner down your drains.
bacon frying in pan
Dont Pour Grease Down the Drain

FATS, OILS & GREASE - Do Not Pour Them Down the Drain!

Dispose of all fats, oils, and grease in the garbage. This includes butter, cooking oils, fry oil, oils, and grease left from cooking meats and/or anything else that gels or solidifies at room temperature. While these will go down the drain or toilet when warm or with soap, they will all gel and solidify as they move down your lateral and the sewer when they cool down or when they mix with other water creating a clog that is very messy and difficult to remove.

When to Get Your Lateral Inspected

Consider hiring a plumber to perform a video inspection of your lateral if:

  • You have a basement back up through the floor drain or other basement fixtures
  • Evidence (debris around the floor drain or in a washtub) that water backed up particularly during wet weather or high use times (shower, laundry)
  • You have periodic slow-running drains or toilets, particularly during wet weather or high use times (showers, laundry)
  • Choose a plumber who uses a sewer camera that can record the video inspection and includes a running footage counter
  • The plumber should record the full lateral video from the house access point to the mainline sewer connection
  • If obstructions or damage are found, have a report/video prepared by the plumber stating the findings and the location (footage) of the blockage or damage. The footage counter allows you to go outside with a tape measure and estimate in your yard where the problem is and what might be in the way to fix it (trees, driveway, sidewalks, etc.)
  • Minor pipe sags (indicated by standing water in the bottom of the pipe)
  • Minor gaps in pipe joints
  • Minor roots, sediment, or groundwater deposits
  • Minor to moderate root intrusion and/or groundwater deposits
  • Pipe cracks
  • Recurring small amounts of sediment, soil, or gravel (less than a handful)
  • Offset pipe joints or breaks that are not disrupting a smooth flow of water
  • Heavy root intrusion
  • Broken, missing, or collapsed pipe
  • Soil or gravel in the pipe that is blocking the flow
  • Offset pipe sections that interrupt the smooth flow

What's the Fix if My Lateral Needs Repairs?

There are many newer repair techniques that do not require digging a large trench in your front yard. However, laterals with serious problems or multiple problems may require digging a trench to install a new pipe from the street to the foundation of your home.

Pipe Bursting – Trenchless Lateral Replacement

Pipe bursting is one type of trenchless sanitary lateral rehabilitation. This method replaces existing buried sewer lateral pipe without the need for a traditional open trench construction along the full length of the existing lateral pipe. This method minimizes the disturbance of your yard while providing a new sanitary sewer lateral from pipe from the house to the sewer main in the street.

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    The Contractor excavates two small pits for pipe bursting.  One pit launches the new pipe, the second pit receives the new pipe. This pit is the receiving pit that includes the compact machine that pulls the new pipe through the old pipe. 

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    This pit is the launch pit. A cable is fed through the old pipe from the receiving pit to this launch pit. The receiving pit machine has enough power to pull the new pipe through the old pipe breaking the old pipe along the way providing a pathway for the new pipe without digging up the entire pipe. 

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    Lawn disturbance is minimized by using pipe bursting methods.  The sanitary sewer lateral is completely replaced using two small excavation pits.

Cured in Place Lateral Replacement - Trenchless Lateral Replacement

Cured in Place Pipe (CIPP) lining is one type of trenchless sanitary lateral rehabilitation.   There are several ways a CIPP liner can be installed. A liner can be installed remotely from the municipal sewer without entering your house, from the sewer cleanout inside your house, or from a sewer cleanout in your yard if you have one. In some cases, a hole needs to be excavated in the basement or the yard to install the liner if other options are not available.

CIPP rehabilitation begins with a televising of a sanitary lateral to determine if the size and condition of the lateral. 

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    The contractor cleans and prepares the lateral by removing deposits, debris, and roots.

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    This is the inside of a typical sanitary lateral after cleaning and preparing the lateral for lining.

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    After the lateral is inspected through closed-circuit televising (CCTV), cleaned, prepped, and measured, the liner material is measured to fit the sanitary lateral.  The Contractor measures each liner to fit each individual sanitary lateral.

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    After the liner material has been cut to size, the contractor mixes the liquid resin that will saturate the liner material.

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    The contractor works the resin throughout the length of the liner material with hand or machine rollers.  The liner material must be completely saturated with the resin before the liner is installed. 

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    Once the liner and resin are fully prepared and ready to install, the liner is rolled up into a pressure tank launcher.

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    The pressure tank launcher is rolled into place near the lateral cleanout in the yard or the basement.

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    The liner can also be loaded into an installation hose and fixture to be installed from the municipal sewer main through a manhole. 

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    Once the pressure tank launcher or the hose and installation fixture are in place, the installation process is similar. Air pressure is applied and the liner “inverts” or rolls out like a rolled-up sock extending the full length of the lateral. Once the lateral liner is inserted in the sanitary lateral, the resin is allowed to cure (harden) for about two to four hours.  The contractor may choose to use steam or hot water circulated through the liner to speed up the curing process.

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    When the lateral liner is cured (hardened), the contractor pulls the “bladder” and all equipment out of the sewer leaving the new liner that should functions like a new pipe. The contractor inspects the lateral and liner with the CCTV camera to confirm the liner has been installed successfully.   This is a completed lateral liner after the resin has hardened.

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    Often the contractor is able to use “vacuum excavation” for any digging that needs to be done. The yard disturbance may only be an area no larger than two-feet square for the entire process. In this case, the contractor installed topsoil and grass seed.

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    Once the liner installation is complete, it is a good idea to have a tag or a similar notification to any plumber that may need to work on the lateral in the future. A lateral liner has several advantages. Your lateral life is greatly extended and most maintenance issues such as root removal are greatly reduced. A successful liner installation is done with little to no digging, so a liner is usually much less cost than a full pipe replacement. The finished liner is similar to new plastic pipe so the use of harsh chemicals such as drain cleaners or aggressive cleaning tools such as cable driven chain root cutters should be avoided. 

Open Cut Repair

Repairing or replacing an existing sanitary sewer by open trench excavation provides a homeowner with a new lateral pipe.  This method requires the most disruption to the property but ensures a completely new sewer lateral pipe to the homeowner. Once the work is completed, the site will be restored to its original condition.

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    Depending on how badly a lateral is damaged, trenchless repair is not always an option. The damage can be caused by age, tree roots, and ground settling. In these cases, an open trench replacement will be necessary.

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    While an open trench replacement can be disruptive to your landscape, it is only temporary. You will have assurance of the long service life that comes with a completely new pipe in the ground. The most common replacement pipe is polyvinyl chloride (PVC plastic).

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    Historically, the water service line was typically buried with the sewer lateral in the same trench. So, often your water service pipe can be upgraded at the same time as your sewer lateral for a relatively minimal cost increase.

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    The contractor may need to complete a spot repair to get your lateral back in service. A spot repair is a short section of new pipe which is connected to the good portions of the existing lateral with a watertight flexible connector on each end of the new pipe. The spot repair may be all you need to restore service or a spot repair may be used to fix a severely damaged section that allows the contractor to complete a full rehabilitation with a trenchless solution to minimize landscape disturbance.