Where does my toilet and sink water drain into?

Your house has two basic systems of water. The first one brings the water into the house, and the second one takes the water out of the house. In other blogs, I have talked about where water in Minneapolis and St. Paul comes from. In this blog, you will learn about where wastewater goes.

Every one of the plumbing fixtures in your house, whether it is a bathtub, toilet, some type of sink, etc., has a wastewater pipe that takes the water away. The smaller fixtures have smaller pipes, and the larger fixtures have larger pipes. All of them eventually join together.

There is a sewer drain in your house that is the main drain. The main is usually located under your basement floor, so you do not see it. It continues underground and into the city sewer main under the street. That sewer main will collect from all of the sewer pipes and drainage from all the houses on the street.

As the main grows larger, all the sewage will eventually make it to a water treatment facility. The water goes through a step-by-step process to get treated. It starts with removing large trash and debris that is taken to a landfill. Then grit and smaller debris are removed, and grease and oil are skimmed off. It is then aerated and disinfected with chlorine and ultraviolet light.

Once the water is fully treated, it is discharged into a local river or body of water. The wastewater facility is charged with treating the water correctly so that it is not harmful. Although it is not potable (drinkable), it is likely to exceed the purity of the body of water into which it is released.

There is a common misconception about wastewater sewers and storm sewers. Years ago, all of the water was merged together in the street, whether it be from rain or sewage and wastewater from your house. There was only one system, and all the wastewater and stormwater went to the wastewater treatment plant.

Within the past few decades, every town has had a push or mandate to separate stormwater from wastewater. It was mandated because it is not necessary to treat the stormwater, and it was becoming too expensive to treat stormwater with the same kind of treatment that must be used for sewage. The grates that you see on the side of the roads are now used for stormwater only and lead directly to a river or body of water without being treated.

Saint Paul Regional Water Services | Saint Paul, Minnesota (stpaul.gov)

Water Department – City of Minneapolis (minneapolismn.gov)

If you have any questions regarding your water or are just looking for a quality plumber in the St. Paul and Minneapolis metro area, give St Paul Pipeworks a call today.

Yours Truly,
Matthew Dettwiler
Social Media Manager


Q: Does toilet wastewater drain into a storm sewer?

A: No, toilet wastewater does not drain into a storm sewer. It is connected to a separate system called the sanitary sewer, which carries wastewater from toilets, sinks, showers, and other household drains to a treatment facility.

Q: What is the difference between a storm sewer and a sanitary sewer?

A: A storm sewer is a system designed to handle rainwater runoff from streets, parking lots, and other surfaces. It collects and carries this water directly to nearby bodies of water, such as rivers or lakes. On the other hand, a sanitary sewer is a separate system that carries wastewater from buildings to a treatment facility, where it is processed and treated before being discharged.

Q: Are storm sewers and sanitary sewers interconnected?

A: No, storm sewers and sanitary sewers are designed to be separate systems. Storm sewers are specifically meant to handle rainwater and prevent flooding, while sanitary sewers deal with wastewater from toilets, sinks, and other drains. The separation helps to ensure that stormwater does not mix with wastewater and overload the treatment facilities.

Q: What happens to toilet wastewater after it enters the sanitary sewer?

A: Once toilet wastewater enters the sanitary sewer system, it travels through a network of underground pipes and is directed to a wastewater treatment plant. At the treatment plant, the wastewater undergoes a series of processes to remove contaminants, such as solids, chemicals, and harmful bacteria, before being discharged into the environment or reused for various purposes.

Q: Is it important to maintain the sanitary sewer system in my home?

A: Yes, it is crucial to maintain the sanitary sewer system in your home. Regular maintenance, including proper disposal of waste, avoiding flushing non-biodegradable items down the toilet, and periodic inspections, can help prevent clogs, backups, and costly repairs. It is also essential to be mindful of what goes down your drains to ensure the proper functioning of the system and to protect the environment.

Does Toilet Wastewater Drain into a Storm Sewer?