Our main service area covers:

  • The Fraser Valley - Surrey, Langley, Maple Ridge, Mission, Abbotsford, Chilliwack, Agassiz, Hope and the Fraser Canyon
  • Sea-to-Sky Corridor - Squamish, Whistler and Pemberton
Septic expert service area

Types of septic systems

Septic System Types & Standards

  • Type One:  Treatment by septic tank only

  • Type Two:  Treatment that produces an effluent consistently containing less than:

    • (i) 45mgl of total suspended solids (TSS) and,
    • (ii) a 5 day biochemical oxygen demand (BOD) of less than 45mg/L.
  • Type Three:  Treatment that produces an effluent consistently containing less than 10 mg/L of total suspended solids and having:

    • (i) a 5 day biochemical oxygen demand of less than 10 mg/L, and
    • (ii) a median fecal coliform density of less than 400 colony forming units per 100.

Type 1: Septic Tank Based Systems

A single septic tank based system consists of an underground container or tank for receiving, and settling wastewater. The solids settle to the bottom of the tank as sludge, while the oil fat and grease float to the surface forming a scum layer.

Anaerobic bacteria (bacteria that do not need oxygen) thrive in the tank, and serve to break down the solid waste. Within a fully functional septic tank, the bacteria are expected to reduce the solids by 50-60%. The liquid between the sludge on the bottom of the tank and the scum on the top (commonly called effluent) flows out of the tank into the disposal area. In a properly designed system, further treatment occurs within the soil, until the liquid effluent is free of pathogens and bacteria, and enters the ground water. The sludge and scum layers which remain in the septic tank are pumped out regularly. This service is provided by septic pumping companies.

Type 2: Secondary Treatment Systems

A typical secondary treatment system uses air (oxygen) to help break down and treat the wastewater. Introducing oxygen to the waste stream will encourage the growth of aerobic bacteria, which are extremely efficient at consuming the solids in waste water. There are many different types of secondary treatment systems available, of varying ability and complexity.

Septic Expert has firm views as to which we prefer. You can visit the “Which treatment system is best?” link to learn more.

Ultimately, secondary treatment systems treat liquid wastewater more efficiently than Type 1 systems, making the effluent cleaner and safer before it is discharged into the disposal area. This is an important consideration to be made when a building site has poor quality soils, or insufficient depth of soil to properly treat effluent. It also allows Septic Expert to specify secondary treatment in order to reduce the size of a drain field. This can be a benefit on a smaller lot where space is at a premium. Treatment prior to disposal into the soil means the soil will not plug over time, and the field will last much longer, so can be reduced in size.

Type 3: Secondary Treatment Systems (for very difficult sites)

Type 3 systems are defined as any septic system using a Type 3 treatment plant and a means of reducing or eliminating pathogens.

The effluent discharged is of a very high quality, and a properly functioning Type 3 treatment plant produces very clear, odourless effluent.

Type 3 treatment plants usually employ aerobic treatment processes (i.e. adding oxygen) to treat domestic sewage, using an integrated air blower to mix oxygen with the sewage. Excellent results can also be achieved using a peat filter. Disinfection is achieved using chlorination/de-chlorination, ozone, or ultraviolet (UV) light. UV systems are most common due to low capital cost and ease of maintenance. Some manufacturers also recommend a sand filter as a means of pathogen reduction.

The vast majority of Type 3 disposal fields are pressurized, and can consist of subsurface trenches, seepage beds, or sand mounds. Type 3 disposal fields are typically smaller than Type 1 or Type 2 fields.

In general, Type 3 septic systems can be used when all of the following site conditions are present:

  1. Soil depth < 15cm (0.5 ft.)
  2. Very rapid or very slow percolation rates
  3. Poor soil structure (no strong platy structure)
  4. Lack of space for a more conventional system.