Over the past few years, Canada has been experiencing an urban exodus with many folks longing to leave the city behind and take up the country life. In rural areas, many homes do not have connections to municipal water and sewer lines as you may be used to. Homeowners may rely on privately owned or communal (shared) wells as their drinking water source, and individual septic systems to treat and discharge their wastewater. The septic system accepts wastewater from the home (sinks, showers, toilets, dishwasher, washing machine), treats the wastewater and returns the treated effluent to the groundwater. A conventional septic system is comprised of two components: a septic tank and a leaching bed. The Home Buyer’s Guide to Septic Systems

Septic Tank

A septic tank is a buried, watertight container, which accepts wastewater from your house (see Figure 4). Septic tanks can be made from concrete, polyethylene or fiberglass and in the past were sometimes made from steel (if the property has a steel tank, it is likely rusted through and needs replacing). Older tanks may be smaller than those found today (the current minimum size in Ontario is 3,600 L (952 US gal).

Current tanks have two compartments while older tanks may only have one compartment. Solids settle to the bottom of the tank to form a sludge layer, and oil and grease float to the top to form a scum layer. The tank should be pumped out every three to five years or when 1/3 of the tank volume is filled with solids (measured by a service provider such as a pumper). Some municipalities require that septic tanks be pumped out more frequently. Bacteria, which are naturally present in the tank, work to break down the sewage over time.

Leaching Bed

The wastewater exits the septic tank into the leaching bed — a system of perforated pipes in gravel trenches on a bed of unsaturated soil (minimum 0.9 m/3 ft. — see Figure 5). The wastewater percolates through the soil where microbes in the soil remove additional harmful bacteria, viruses, and nutrients before returning the treated effluent to the groundwater. In cases where there is more than 0.9 m (3 ft.) of unsaturated soil from the high water table or bedrock, a conventional system is used, where the network of perforated drainage piping is installed either directly in the native soil, or in imported sand if the native soil is not appropriate for treatment. In cases where the groundwater or bedrock is close to the surface, the leaching bed must be raised 0.9 m (3 ft.) above the high water table or bedrock. This is called a raised bed system.

Alternative Systems

Under certain site conditions such as lot limited area, high groundwater table or poor soil conditions (clay or bedrock for example), a conventional system will not provide sufficient treatment of the wastewater. Under these conditions, it is often possible to install an alternative treatment unit. The two most common types of alternative treatment units are trickling filters, where the effluent from the septic tank trickles through an unsaturated filter media (such as peat or a textile filter), and aeration systems, where the effluent from the septic tank passes through an aerated tank.

Alternative treatment units provide a higher level of wastewater treatment, allowing the effluent to be discharged to a smaller area than in a conventional leaching bed. Effluent from an alternative treatment unit can also be discharged to a shallow buried trench, which is a pressurized pipe system 15 cm (6 in.) below the ground surface. In most provinces, homeowners with alternative treatment units are required to have a maintenance contract with a service provider to inspect and maintain their systems.

Inspecting the Septic System

You should have the septic system inspected by a certified on-site system professional (such as a certified installer or engineer) before purchasing the home. Call your local municipal office, public health office or Ministry of Environment office for a list of qualified professionals.

The inspection should include a discussion with the homeowner, a review of the system permit, a tank inspection, a leaching bed inspection, and a house inspection.

System Replacement or Repair

A septic system should last anywhere from 20 – 25 years, or even longer if it is correctly installed and maintained with regular pump-outs every three to five years.