Water Legislation and Substance/Quality Database Canadian Water and Wastewater Association

Frequently Asked Questions
Private Onsite Wastewater Treatment
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What is the difference between a sewer system and an onsite treatment system?
A sewer system is a series of pipes that collect wastewater and transport it to another location where the wastewater is processed by a municipal treatment system. An onsite treatment system collects, treats and disposes of wastewater from a single source in the same location that it is generated. Municipal and onsite treatment systems utilize many of the same treatment processes, but a municipal sewer system collects and treats wastewater from many different locations.

Why are onsite systems necessary? Why don't they just run sewers everywhere?
Population density, the topography of the area, soil conditions and numerous other factors are involved in the construction and operation of a sewage collection system. Increasing migration to suburban and rural areas make municipal sewers more difficult and costly to build and maintain. Onsite treatment systems are often the most practical and cost-effective solution for wastewater treatment and disposal in small rural and remote communities.

What is a septic system?
The most common type of onsite sewage system is septic system. Basically a septic system provides a holding tank where natural bacterial action decomposes human waste products into environmentally acceptable components - the major end-components being water, mixed with some other components that are not readily consumed by the bacterial action, gases, and undigested solids. The end products, except the undigested solids, are then discharged to the on-site environment.

How can I maintain my septic system?
The undigested solids (sludge) in the bottom of the septic tank should be pumped out every two to four years, depending on usage and tank size. If the sludge is not removed periodically, it will eventually carry over into the leach field and cause the field to fail.

A well designed system can handle a reasonable amount of normal household chemicals such as drain cleaners, laundry detergent and bleach; excessive usage can be detrimental. You should avoid putting in chemicals that are toxic to the beneficial bacteria degrading the wastes, such as paint thinner, solvents, insecticides, etc. Cooking fats and grease should also be avoided. If a garbage disposal is used, more frequent tank pumping may be needed.

Depending on the size of the tank and your location, plan on a cost of about $200 each time the tank is pumped. When the tank is pumped, your service person should also check the tank baffles for possible damage; ask them to do this inspection before you contract with them. While the tank is open, the service technician can also run some water from a hose into the distribution box to get an indication that the leach field is also still functioning; ask if the company offers this service.

What alternatives are there to septic systems?
There are several alternatives to a conventional septic system. These include a "mound" system. In a mound system, a suitable soil is placed above the unsuitable soil. A conventional system is then installed in the mound. There are some additional requirements for this type of design.

If there is not enough room for a conventional leach field, it may be possible to install one or more cesspools, or seepage pits. These units are usually round, require less open ground, and are deeper than a conventional leach field. Again, there are specific requirements for these systems.

Conventional, mound, and seepage pit systems all work by what is called anaerobic bacterial action. This means the bacteria work without oxygen. Some systems are designed to be aerobic - meaning the bacteria need oxygen (air); There are also hybrid systems that use a combination of anaerobic and aerobic sections.

Other systems that have been used include: peat systems; solar aquatics; and small wetland systems. There are trial systems in various parts of Canada. Since these require approval by the provincial/territorial jurisdictions, information for your own specific area should be requested from that jurisdiction.

Where can I find information on onsite sewage treatment in my province?