Septic Systems


Septic tank systems treat residential wastewater onsite by retaining raw waste for a length of time to allow fats, oils and grease to float to the surface (scum) and other waste to settle to the bottom of the tank (sludge). The remaining fluid is dispersed into a leaching field that also provides treatment through aerobic digestion and adsorption within the stone bed and adjacent soil. Anaerobic digestion continues within the tank.  Retention time is affected by the thickness of the floating layer and the settled layer which can lead to poor treatment and failure of the leaching field due to clogging if not maintained properly.

Cross section of house diagram showing location of septic tank.


How to find your septic system

If you are unsure where you septic system is located, use one of the two following options.

  1. Follow the provincial government’s brochure on How to Find a Septic Tank (PDF)
  2. Request a copy of your onsite sewage disposal system site plan from your local Island Health office

Unit 202 - 6425 Norcross Road (Duncan Norcross Drinkwater Building)

Duncan, B.C.

V9L 6C5

Phone: 250-737-2010

Fax: 250-737-2008


Septic tank pumping

Septic tanks need to be pumped out regularly to ensure proper function and retention. Appropriate intervals depend on factors such as tank size, waste volume and composition, weather, and type of treatment system. In British Columbia, the provincial recommendation is to pump out your septic tank every three to five years, with smaller tanks needing to be pumped more frequently. Regularly pumping of a septic tank can help:

  • Protect the environment: failing septic systems can cause surface water and groundwater contamination
  • Protect your property: septic failures can cause damage to your home or present a health risk to your family or neighbours
  • Mitigate costs: Septic system repairs and replacements can be very expensive

Septic systems are regulated by the Sewerage System Regulation, which requires an Authorized Person to install, maintain and repair septic systems. To find an Authorized Person use the following links:

  • Registered Onsite Wastewater Practitioner (ROWP) through ASTTBC
  • Professional Engineer or Professional Geoscientist through EGBC

Additional resources