BC classifies septic systems by the quality of effluent they produce, not by brand or shape. Type 1 is treatment by septic tank only. Type 2 must consistently produce effluent under 45 mg/L of total suspended solids with a 5 day biochemical oxygen demand under 45 mg/L. Type 3 tightens both to under 10 mg/L and adds a fecal coliform limit. Your soil decides which one you need.
Homeowners usually meet these labels partway through a quote, when a designer explains why the neighbour’s $25,000 system will not work on their lot. Here is what the classes actually mean, what pushes a Fraser Valley property up a level, and what each step costs.
What are Type 1, Type 2 and Type 3 systems?
They are effluent quality standards written into the Sewerage System Regulation. Nothing about tanks, mounds or trenches appears in the definitions. Only the water coming out.
| Class | What the regulation requires | What it looks like on the ground |
|---|---|---|
| Type 1 | Treatment by septic tank only | Septic tank feeding a gravity or pressurized dispersal field |
| Type 2 | Effluent consistently under 45 mg/L total suspended solids, 5 day BOD under 45 mg/L | Septic tank plus a secondary treatment unit ahead of the field |
| Type 3 | Effluent consistently under 10 mg/L total suspended solids, 5 day BOD under 10 mg/L, median fecal coliform density under 400 CFU per 100 mL | Secondary treatment plus disinfection |
Two things follow from that framing. First, a sand mound is not a “Type 2 system”; it is a dispersal method, and Type 1 sand mounds are the standard answer on much of the valley floor. Second, moving up a class is not an upgrade you buy for comfort. It is a substitution: better effluent lets the site get away with less soil.
What actually decides which type you need?
Vertical separation: the depth of unsaturated native soil under the field. The Standard Practice Manual sets a minimum for every combination of soil, distribution method and effluent type, and that single number drives almost every design decision on a Fraser Valley lot.
Some of the manual’s gravity-distribution minimums show how tight the margins get:
- Gravelly sand and coarse sands: 150 cm of native soil, all effluent types
- Fine sand, sandy loam and loam: 90 cm for Type 1 or Type 3 effluent, 120 cm for Type 2
- Silt loam and silt: 120 cm, all effluent types
Now put that against a Sumas Prairie or Nicomen Island winter, where the water table climbs to within centimetres of the surface. There is no 120 cm of dry soil to be had. The design has three legitimate moves: import soil depth, treat your way to a smaller requirement, or move the field to better ground.
That is why the same three-bedroom house gets a $25,000 quote in Bradner and a $60,000 quote in Greendale, and why both quotes can be honest. Our Fraser Valley high water table guide covers what this means for owners who already live with a system in that ground.
Why do so many valley lots end up with a sand mound?
Because a mound is the cheapest way to manufacture vertical separation that does not exist. Under the same manual, a sand mound needs as little as 25 cm of native soil vertical separation, with engineered sand supplying the remainder of the required depth.
Read that against the 120 cm a gravity field needs in silt and the arithmetic is obvious. Trucking in sand is expensive, but it is cheaper and more durable than fighting the water table any other way, and it is why mounds sit in so many valley-floor yards. Published Fraser Valley pricing puts a Type 1 sand mound at $55,000 to $65,000 against $20,000 to $30,000 for a gravity system on cooperative soil.
A mound also changes what the yard looks like and how it gets used. Nothing drives on it, nothing gets built on it, and the cover vegetation matters. That is a real trade, and it is worth understanding before the quote arrives rather than after the sand does.
What does each type cost to build and to own?
Every step up buys a buildable site and hands you an annual line item. Capital cost is only half the comparison.
| Type 1 gravity | Type 1 pressure distribution | Type 1 sand mound | Type 2 or 3 added | |
|---|---|---|---|---|
| Indicative build cost | $20,000 to $30,000 | $35,000 to $45,000 | $55,000 to $65,000 | Adds $15,000 to $65,000 |
| Moving parts | None | Pump, floats, panel | Pump, floats, panel | Treatment unit, blowers or media, controls |
| Power required | No | Yes | Yes | Yes |
| Maintenance plan servicing | Pumping only | Pumping plus pump checks | Pumping plus pump checks | Scheduled service contract |
| Fails quietly? | Rarely | Alarm warns you | Alarm warns you | Alarm and service reports warn you |
Indicative construction ranges are published Fraser Valley figures as of 2026, from a Langley installer and a February 2026 Fraser Valley land development guide. Design fees of $3,200 to $5,200 and a $200 Fraser Health filing fee apply to all of them. Full breakdown in our new septic system cost guide.
The honest rule: choose the simplest system your soil will actually support. A Type 3 train on a lot that only needed pressure distribution is money spent on complexity, and complexity is the thing that phones you at 11pm.
Can site drainage change which type you need?
Sometimes, and BC’s own manual says so, but only with evidence. The Standard Practice Manual has a whole section on site drainage, describing interception drains, also called curtain drains, which divert water away from the dispersal area and lower the water table, and relief drains that do the same for flat sites with groundwater mounding.
The manual is careful about it, and so should you be. It states that where a drainage system is being relied on to lower the water table in order to achieve vertical separation standards, it is best to pre-install the drainage system and confirm by measurement that it actually lowers the water table far enough. In other words, drainage can change the answer, but only if it is installed first and proven, not assumed on a drawing.
Separately from the design question, keeping surface water off an existing field is straightforward good practice. The US EPA’s guidance is to keep roof drains, sump pumps and other rainwater drainage systems away from your drainfield area, and on flat valley lots that is not automatic. Intercepting yard and roof water before it reaches the bed is yard drainage and French drain work, a separate trade from septic, and anything cut inside the field’s setbacks needs to be checked with the Authorized Person responsible for the system first.
Who is allowed to design each type?
A registered practitioner can handle Type 1 and Type 2. Type 3 needs an engineer. The regulation defines an Authorized Person as a registered practitioner or a professional, and the Province is specific about the split: registered onsite wastewater practitioners are qualified to design and construct Type 1 and Type 2 systems only, while professional engineers may also design and construct Type 3 systems.
Whichever you hire, the process is the same: they file the plans and specifications with the health authority before construction, and file a signed letter of certification within 30 days of finishing. In the Fraser Valley the filings go to Fraser Health. Keep both documents with the house papers, because a buyer’s inspector will ask for them, and their absence is a negotiating fact.
The short version
Type is an output standard, not a product. Your soil and your water table decide it, the site evaluation is what reveals it, and the cheapest system to own is the simplest one your ground can carry. If your existing field is struggling and someone has raised the idea of moving up a treatment class, get the diagnosis first: see drain field repair and replacement for how that decision gets made honestly.
Building, replacing or trying to make sense of a design quote in Abbotsford, Chilliwack, Mission, Langley or Agassiz? Call (604) 800-7217 or request a quote.
Frequently Asked Questions
What is the difference between Type 1, Type 2 and Type 3 in BC?
They are effluent quality classes set by the Sewerage System Regulation. Type 1 is treatment by septic tank only. Type 2 produces effluent consistently under 45 mg/L of total suspended solids with a 5 day biochemical oxygen demand under 45 mg/L. Type 3 tightens both to under 10 mg/L and adds a median fecal coliform density under 400 colony forming units per 100 mL.
Is a sand mound a Type 2 system?
Not necessarily. A mound is a dispersal method, not a treatment class, and Type 1 sand mounds are common in the Fraser Valley. Mounds and treatment units are two different ways of solving the same problem, which is not enough unsaturated soil under the field. Some sites use one, some use both.
Can a ROWP design a Type 3 system?
No. The Province states that registered onsite wastewater practitioners are qualified to design and construct Type 1 and Type 2 systems only, while professional engineers may also design and construct Type 3 systems. Both count as Authorized Persons under the regulation, so ask which one your designer is before the site evaluation.
Does a Type 2 system mean I never have to pump the tank?
No. A treatment unit sits downstream of a septic tank that still accumulates sludge and scum, and the unit itself needs regular service. Type 2 and Type 3 systems come with a maintenance plan under the regulation, and following that plan is an owner obligation, not a suggestion.
Can I upgrade an existing Type 1 system to Type 2 to fix a failing field?
Sometimes, and it is a legitimate strategy where the field is failing because it never had enough vertical separation. Better effluent quality can allow a smaller or shallower dispersal area. It is Authorized Person work with a filing, and it only helps if poor site conditions rather than solids carryover caused the failure, so diagnosis comes first.
Which type is cheapest to own over 20 years?
Type 1 gravity, by a wide margin, because it has no pump, no control panel, no treatment media and no service contract. Every step up buys you a buildable site at the cost of an annual line item. Choose the simplest system your soil will actually support.
Published August 20, 2026 · Last updated August 20, 2026 · Fraser Valley Septic