Septic services · Duncan
Septic System Installation in Duncan
New and replacement septic systems — designed for Cowichan Valley soils and filed with Island Health.
Duncan Septic Systems installs new and replacement septic systems across Duncan, Cobble Hill and Shawnigan Lake. Most new systems here land between $15,000 and $45,000, depending on the type your soil needs. We design, install and file Type 1 and Type 2 systems ourselves, and our installers are ROWP-registered. Where a lot needs a Type 3, an engineer draws it and we build it. Your first assessment is free.
Every install includes the soil evaluation, the system design, and the Island Health filing, with a Letter of Certification on completion.
Choosing the right system — Type 1, 2, or 3
A Type 1 is the basic setup — a tank and a drain field. It works on open lots where the soil takes water. Where soil is tight or the water table is high — common across the valley floor — a Type 2 adds a treatment unit. It cleans the water more, so you can get away with a smaller field. On sensitive sites near Shawnigan Lake or Cowichan Bay you usually need a Type 3, which treats it further again. We dig test pits and read the soil, and that tells us which one you need.
Soil evaluation, design, and the Island Health filing
Every new or replacement system starts with soil and site testing to read percolation, water table, and setbacks from wells and watercourses. For Type 1 and Type 2 systems, we design the system as an Authorized Person and file it with Island Health before any digging; for Type 3, a professional handles the design and filing, and we build to their plans. Design, testing, and filing usually run $2,000 to $3,000 and are built into the quote.
Replacing an old or failed system
Many Cowichan installs are replacements — an older system whose drain field has finally worn out. Where the original field has failed, we build a new drain field and often step the property up to Type 2 treatment. That brings the property back onside and stops sewage surfacing in the yard.
How a Cowichan Valley septic install works
- 1
Site & soil evaluation — We test soil percolation, check the water table, and map setbacks from wells, property lines, and watercourses.
- 2
System design & Island Health filing — We design Type 1 and Type 2 systems ourselves and file them with Island Health before construction starts; for Type 3, a professional designs it and we build to their plans.
- 3
Installation — We install the tank, the treatment unit if the design calls for one, and the drain field, exactly to the approved design.
- 4
Letter of Certification — We file the Letter of Certification that makes the system legal to use, and hand you the maintenance plan.
Local conditions
The clay on the valley floor drains slowly, and the low lots by the Cowichan and Koksilah rivers sit wet all winter. On ground like that we usually put in a Type 2 with a raised or sand-lined field. If you're right on the lake or the estuary, you usually need a Type 2 or Type 3 to protect the water.
In practice
- Situation
- A Cobble Hill family's 1980s septic system was surfacing sewage in the yard and failed inspection before a sale.
- Complication
- Tight clay soil and a small lot ruled out another conventional gravity field, and the buyers' financing hinged on a compliant system.
- Resolution
- We designed a Type 2 treatment system with a compact sand-lined field, filed it with Island Health, installed it, and certified it in time for the sale to close.
People also ask
How long does a septic system last?
Most systems we see last 20 to 30 years, and the drain field usually goes first. It goes sooner if you skip your pump-outs.
How long does a septic installation take?
Most residential installs take a few days of on-site work, but the full timeline — soil evaluation, design, and the Island Health filing — usually runs a few weeks from first visit to a system ready to use.
Can I install a septic system myself?
No — BC's Sewerage System Regulation requires an Authorized Person, a ROWP or a Professional, to design, install, and file the system. That's the part we take off your hands.
For related help, see septic repair and septic inspection, or compare typical prices in the septic cost guide. We also work in Cobble Hill and Shawnigan Lake.
Ready for a septic installation quote in Duncan?
We offer free on-site assessments across the Cowichan Valley Regional District.