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Water Quality

Onsite Sewage Systems

Onsite Sewage Systems > Solutions > References and Links

Onsite Sewage Systems

Onsite sewage systems are effective at treating household sewage if designed and installed properly in appropriate soil and maintained regularly. In typical onsite sewage systems, the wastewater from toilets and other drains flows from your house into a tank that separates the solids and scum from the liquid. Bacteria help break down the solids into sludge. The liquid flows out of the tank into a network of pipes buried in a disposal field of gravel and soil. Holes in the pipes allow the wastewater to be released into the disposal field. The soil, gravel and naturally occurring bacteria in the soil filter and cleanse the wastewater. There are about 250,000 onsite sewage systems in British Columbia, despite expansion of municipal sewage collection and treatment facilities.

drawing of onsite sewage system

Typical onsite sewage system (adapted from the Soap and Detergent Association)

Onsite systems that are poorly planned, constructed or maintained present substantial threats to water quality in the province. Onsite sewage systems can fail and untreated wastewater can be carried to nearby waterbodies threatening human health, causing excessive algal growth and harming aquatic life. If your onsite system is not properly located on your property or does not have an appropriate depth of suitable soil, the system may not fully treat the wastewater. The wastewater can seep down into the ground water polluting drinking water supplies or rise to the surface and flow over land into nearby waterbodies. If you don't have your septic tank pumped out regularly, the solids and scum can flow into the drainfield and plug it up. If the drainfield gets clogged, untreated wastewater can rise to the surface threatening your family's and neighbors' health, reducing the value of your property and creating odours and the need for costly repairs. Heavy use of strong disinfectants can kill the beneficial bacteria in the soil around your disposal field and reduce the natural cleansing function of your system. Finally, if you use too much water in your home, wastewater can be flushed out too quickly and solids can flow into the drainfield, causing it to plug. The less you flush or pour down your drains, the better your system will work.

You may have a failing onsite sewage system if you notice one or more of the following signs:

  • unusually green or spongy grass over the system;
  • toilets, showers and sinks back up or take a long time to drain;
  • sewage surfacing on your lawn or in a nearby ditch;
  • sewage odours around your yard, especially after rain.

Alternative sewage disposal systems are available to replace conventional onsite systems. These systems can stand alone or be used in combination with conventional systems. They not only can reduce the impact of the conventional onsite sewage disposal systems on water quality, but can reduce the amount of waste produced. Alternative sewage disposal systems can produce high quality effluent and conserve water through low usage.

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The following tips will help you prevent NPS pollution from your onsite sewage system:

  • You must obtain a permit from the local Health Authority before installing, repairing or upgrading an onsite sewage system. This will ensure that your system meets local requirements for density, setbacks, size, location and construction.
  • Take the time to be aware of your system — owners have to play a role in the management and maintenance of their system. Create a map of your lot showing the location of the onsite sewage system and leave it for the next owners.
  • Have your system inspected yearly and pumped out every 2 to 5 years by a qualified septic service company. Regular pumping and routine maintenance of all system components is cheaper than having to rebuild a drainfield.
  • Upgrade your onsite sewage system when you upgrade your home (i.e., when you add a bedroom or a suite).
  • Practice water conservation — use water wisely. For example, run the dishwasher only when full and use low-flow showerheads and toilets.
  • Don't use garburators — this will reduce the amount of solids and grease you put into the system.
  • Don't put toxic chemicals down the drain because they can kill the bacteria at work in your onsite sewage system and can contaminate waterbodies.
  • Avoid pouring grease or fats down the drain.
  • Use biodegradable household cleaners instead of bleach or other hazardous products.
  • Avoid flushing pet wastes into the system — bury them away from the drainfield instead.
  • Don't drive, pave or put heavy objects or machinery over the drainfield.
  • Avoid planting trees or shrubs near the drainfield because their roots can damage or plug the pipes.
  • Don't over-water the drainfield or allow roof or perimeter drains to run onto the drainfield.
  • Don't use septic 'starters' or similar products; they are unnecessary, expensive and may cause pollution.

photo of maintenance of sewage system

Regular inspection and maintenance will maximize the life and performance of your system

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References and Links

The National Small Flows Clearinghouse. United States Environmental Protection Agency.

The Septic Information Website.

Tackling Non-Point Source Water Pollution in British Columbia: An Action Plan. 1999. Ministry of Environment, Lands and Parks.

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