Source water facts: Septic systems

What are septic systems?

A septic system is a private sewage treatment system. Household wastewater flows into a septic tank where solid and liquid separation occurs. Solid waste settles to the bottom of the tank where it is mostly broken down by bacteria. Remaining solids are pumped out at regular periods, usually every five years. Liquid waste flows through a series of pipes that slowly release into a leaching bed which filters water before it enters the ground.

Illustration of septic tank and leaching bed

Where are septic systems found?

Septic systems are commonly found in rural areas where there is no municipal water service or sewer pipes for homes, farms or businesses to connect to. Some properties in the City of Guelph have septic systems.

Why might septic systems be a threat to our drinking water sources?

Septic systems can pose a threat to our drinking water sources when they aren’t properly maintained. If damaged, septic systems could allow contaminants, such as chemicals and bacteria, to seep into groundwater and surface water.

Regular septic system inspections and maintenance help to prevent costly system failure, and protect our drinking water sources as well as the environment.

What can I do to protect our drinking water sources from septic system threats?

Perform regular maintenance and checks on your septic system

  • Have your septic system inspected on a regular basis and maintain it to manufacturer’s instructions. The Ontario Building Code requires that septic systems within identified vulnerable areas around municipal drinking water sources be inspected every five years.
  • Keep records of pumping, maintenance and repair.

Be careful what goes into your septic system

  • Your septic system is not a waste disposal system. Improper waste can clog your leaching bed and pipes, leading to costly repairs.
  • Dispose of household hazardous waste safely and free of charge at the City of Guelph’s Household Hazardous Waste Depot: visit for more information about hours of operation and acceptable materials
700 kBSource water protection fact sheet: septic systems (PDF)

For more information

519-822-1260 extension 3320