Private Sewer Laterals – Everything You Need to Know

A sewer lateral is the pipe which carries waste from your house to the public sewer line in the street. There is the upper lateral which is the pipe between your house and the property line, and the lower lateral which connects the upper lateral to the public sewer line outside your property.

Image Credit: Sonoma City

Private Sewer Laterals: Key Points to Know

  • Definition: Private sewer laterals are the pipes that connect individual properties, such as homes and businesses, to the public sewer system.
  • Ownership: Private sewer laterals are typically owned and maintained by the property owner or the responsible entity, not the municipal or public sewer system.
  • Function: They serve as the link between a property’s plumbing system and the public sewer or septic system, carrying wastewater and sewage away for treatment or disposal.
  • Materials: Private sewer laterals are often made of various materials, including clay, PVC, cast iron, or concrete, depending on local building codes and historical practices.
  • Maintenance Responsibility: Property owners are responsible for the maintenance and repair of their private sewer laterals, including addressing blockages, leaks, and other issues.
  • Blockages: Common problems with private sewer laterals include blockages caused by tree roots, grease buildup, debris, or structural damage.
  • Inspections: Periodic inspections of private sewer laterals are essential to identify issues early, ensuring proper function and preventing costly repairs.
  • Repair and Replacement: If a private sewer lateral is damaged beyond repair, property owners are typically responsible for the cost of replacement.
  • Regulations: Municipalities often have regulations governing private sewer lateral maintenance and repair to protect public health and prevent pollution.
  • Leakage Risks: A damaged or leaking private sewer lateral can contaminate soil, groundwater, and nearby water bodies, posing environmental and health risks.
  • Professional Help: Property owners may need to hire licensed plumbers or sewer service professionals to inspect, maintain, repair, or replace private sewer laterals.
  • Insurance Consideration: Property owners may want to check if their homeowner’s insurance covers private sewer lateral repairs or damages.
  • Pre-purchase Inspection: Homebuyers may opt for private sewer lateral inspections before purchasing a property to avoid unexpected repair costs.
  • Trenchless Technology: Some repair methods, like pipe lining or pipe bursting, offer less invasive options for repairing or replacing damaged private sewer laterals.
  • Environmental Impact: Proper maintenance of private sewer laterals is essential to prevent sewage leaks and contamination that can harm the environment.

How Does a Sewer Lateral Work?

Every property needs a way to remove wastewater from all the drains in the house. And that is where sewer laterals come in.

Unknown to most people, kitchen sink waste and waste from toilet drains into the same sewer lateral. A house has only 1 sewer lateral. That is why it is not unheard of for sewage to back up from your kitchen sink.

Unlike water which is usually under pressure, sewer laterals depend on gravity to carry wastewater from your house to the public sewer lines.

As a result, the sewer laterals are installed strictly with a calculated slope so that the waste can flow out on its own. If they are too flat, they will clog and backup frequently while if the slope is too steep the water will flow too fast leaving the solids behind again resulting in clogs and sewer backups.

The required slope on sewer laterals is 2% or ¼ inch for every 1 foot of pipe. You can however increase the slope to as high as 3 inches for every foot of pipe if the lateral is too long or if takes corners through the yard.

Image Credit: Long Beach Water Dept.

The upper lateral is the one between your house and your property line. That is usually at the sidewalk in the street. Whenever possible, this section should be in a straight line but it can curve around if there are obstacles in the yard.

The lower lateral connects the upper lateral to the city’s main sewer line. Since the city’s sewer line is installed very deep in the ground and a few feet away from the property line, the lower lateral has a bigger slope than the upper lateral.

As I had earlier mentioned, in most cases the lower lateral will be the responsibility of the homeowner despite it being on the public side. In some areas it could however be the city’s responsibility so check with your city.

It becomes a problem when you need to repair the lower lateral. Being on the public side, your work will impact the public and you will need to inform the city in advance.

The city will also need to ensure that the job is being done by a licensed professional and that all the plumbing codes are strictly adhered to.  They will also want the job done safely and with minimal inconvenience to the public.

I don’t recommend DIYs in as far as sewer laterals are involved. This is an area you want to leave to the professionals.

Most sewer laterals are 4 inches in diameter and that is actually the minimum size as per the code. Some are however 6 inches in diameter especially those designed to serve multifamily dwellings.

In the past, sewer laterals were made of clay or cast iron and most homes still have those pipes in place. Currently PVC is the most preferred material for sewer laterals.

PVC sewer laterals are cheap, easy to install and do not corrode or crack, meaning they are not affected by tree roots which are notorious for causing clogs and sewer backups. That is the main problem with clay and cast iron sewer laterals.

What is Sewer Lateral Cleaning/Inspection?

Sewer lateral cleaning or inspection involves the use of a sewer camera to check the condition of the sewer line. Thereafter, a drain snake fitted with different sizes of blades is used to cut tree roots and basically clean the inside of the line. A hydro jetting unit can also be used.

Sewer laterals in most houses have a sewer cleanout. This Sewer cleanouts are actually required by the code just that old houses may not have them.

A sewer cleanout is a small section of pipe connected straight on the upper lateral. In some houses it could be inside the house (usually in the basement) but in others it is located outside the house.


A sewer cleanout gives access to the sewer line. If there is sewer backing up in the basement or you drains are just too slow and you suspect a clog in the lateral is the problem, you use the cleanout to gain access to the sewer line.

In instances where the house has no cleanout, a plumber will have to remove the toilet or access the sewer line from the plumbing vent on the roof of the house. That will however cost more and the plumber will most likely not warranty the work.

Sewer lateral inspection/cleaning are very important. You wouldn’t know that if you have never experienced sewer backups

Having sewage backing up in your house is not only inconvenient, a health hazard but it costs thousands of dollars to fix. It is even worse since homeowners insurance does not cover sewer backups.

What you need to understand is that sewer laterals do not just clog and back up in an instance. It is usually a gradual thing.

By having your sewer lateral inspected frequently, you will be in a position to avert the danger before it happens. Selling a house will also be easier if you have had your sewer lateral inspected and passed.

In sewer line inspection, a plumber will feed a sewer inspection camera inside the lateral via the sewer cleanout and you can see the condition of the inside of the sewer on a screen. The camera can see cracks, tree roots, blockages etc.

After the sewer lateral inspection, the plumber will recommend the best way to clean it. This will either be snaking or hydro jetting.

A sewer lateral inspection costs anywhere between $200 and $800. The costs depends on where you live, the company doing the job, the type of equipment being used for the job as well as the scope of work.

It is not a cheap undertaking but I can guarantee you it is small price to pay compared to what you would have to deal with when the sewer lateral starts to leak or even backup in your house.

Ideally, sewer laterals need to be inspected and cleaned often especially if you have an old line or there are lots of trees in your property or neighborhood. Once every 2 to 5 years would be my recommendation.

Cast iron and clay sewer laterals will last for 50 to 100 years depending on how well they are maintained. PVC laterals can however last for more than 100 years.

How Do I find my sewer Lateral?

Unless you know where to look, sewer laterals are not that easy to find. This is because they are installed underground and could be passing through anywhere in your yard.

The easiest way to locate a sewer lateral is my finding the sewer cleanout. As I had mentioned, sewer cleanouts are connected directly to the upper sewer lateral.

If your sewer cleanout is located in the house, it will be in the basement connected to the main house drain line or directly on the floor. Take your time to find it since some people prefer hiding them inside closets or under carpets.

Outside your house, look for a 4-inch pipe sticking a few inches from the ground. It will be very close to the house with a square nut at the top of the cap. Some houses have 2 cleanouts.

If you cannot find the sewer cleanout, you can call or visit the city water and sewer department. Since your sewer lateral is connected to their main sewer line, they will have a map where they can show exactly where your sewer lateral is.

Another thing you can do is call the old house owner and ask them. Chances are that they had worked on the sewer line and therefore know where the lateral is.

If you can’t get hold of them, check in the home inspection report (you got that while buying the house) if there is schematic of the drain-waste-vent system. Most likely there will be one.

One of these methods will surely help you find your sewer lateral. Otherwise you can look for an interactive underground utility map for your area online.

Sewer Lateral Problems

The following are the most common problems with sewer laterals:

1. Aging Pipes

Old pipes which were made of cast iron and clay are susceptible to cracks which is PVC pipes are now preferred. Cracks will result in leaks and you are likely to see lush green spots in your yard when that happens or even a sewage smell outside your house.

Corroded cast iron pipes and old collapsing clay sewer laterals will reduce the wastewater flow rate and you are more likely to see your fixtures draining slowly when that happens.

2.Sewer Back Ups

When sewer laterals age, they clog a lot. Clogs in sewer lines almost always mean sewage backing up to your house.

As I had mentioned, most of these clogs are caused by tree roots which grow through the cracks on the pipes. Pouring of grease down the sink drain is also another cause of sewer backups.

3. Soil Shifting

Soil movement around your property (it happens) can cause sewer laterals to be subjected to more pressure than they can hold resulting in cracks and leaks.

Never move heavy machinery above sewer laterals to prevent the same from happening. Natural disasters like earthquakes are however unpreventable but that is usually covered by your insurance.

Sewer Lateral Replacement

Sewer lateral replacement is not a cheap thing. If however after an inspection the plumber recommends that you do it, you should definitely do it.

Luckily, there is a relatively new way of replacing sewer laterals known as trenchless sewer replacement. This method does not involve digging deep trenchless in your yard.

The method will however not work for all sewer laterals. If your line is extensively damaged then you will need a complete replacement which involves digging.

In trenchless sewer replacement, the old/damaged sewer lateral is used as a host for the new one. The work is done via the sewer cleanout or by removing a toilet if there is no cleanout.

To start with, the sewer lateral is thoroughly inspected and when deemed a good candidate for the job it is cleaned via hydro jetting.

Afterwards, a flexible epoxy saturated liner/tube is installed directly inside the existing lateral. After some time the epoxy cures/hardens forming a new line inside the old one.

This method is cheaper and fast compared to digging a trench throughout your yard. You however need to work with a reputable company.

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