What is a Sewer Main or Main Drain?


The hot pink pipe in the image above is the home’s sewer main!

A sewer main is also known as a main line or main drain. A building’s sewer main collects sewage from all of the building’s branch lines and carries it into the public sewer. In other words, your sewer main is the only thing that transports sewage from your home, office, or other building to the city’s sewer.

Sewer Main Facts

All new main lines are made of PVC, polyvinyl chloride, but many older lines are made from cast iron or clay piping. Cast-iron pipes are notorious for rusting out underground and being very prone to clogging. Clay pipes last much longer than cast iron, but are much more fragile and prone to roots. Overtime, large gaps form between the different sections of clay pipes, because they are fitted together, not glued or threaded. Trees can grow on the side of a mountain, so if there are any gaps in the pipes, roots will find their way in! Because of this PVC pipes have become the gold standard. PVC has been used since the 1970s and is not going anywhere any time soon! It never rusts, is very sturdy, and is completely water tight! Tree roots can penetrate PVC pipes, but it is far less likely than with clay or cast iron.

Here is more information on what causes sewer mains to backup.

Most homes have a 4 inch main. However, in some cases they may have a 3 or 6 inch main.

Who is Responsible for the Sewer Main?

A right of way is a property line for plumbing. The right of way is important, because if there is an issue with a sewer main, the right of way is used to determine who is responsible to pay for the repairs. The property owner is responsible for maintaining the plumbing on their side of the right of way and the city is responsible for maintaining any plumbing on their side of the right of way. The city’s right of way starts at the road or sidewalk. Most people assume that ownership stops or starts at property line, but this is not the case for plumbing.

Interested in Learning More About Your Home’s Plumbing?

1-Tom-Plumber’s blog and Facebook page are a great resource for everything you could want to know about plumbing! Need an expert opinion? Give us a call at 866-758-6237 and set up a consultation today?

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