Septic System Installation Cornwall — Built to Last
Building a new home, replacing a failed leaching bed, or buying a rural property the inspector flagged? We handle the whole job — soil testing, the South Nation Conservation permit, excavation and final inspection — across Cornwall, Long Sault, Ingleside, Lancaster, Alexandria and rural SD&G. One written price, one crew, no surprises.
Septic Installation in Cornwall — New Builds & Full Replacements
Three situations bring people to this page: you're building on a rural lot and the house can't be occupied without a working system; your leaching bed has finally failed and every pump-out buys you a few weeks at best; or you're buying a property outside Cornwall and the inspection came back with "system at end of life." In all three, the clock is running and nobody wants to coordinate a soil tester, an excavator and the permit office themselves.
We do all of it as one licensed installer: soil evaluation, the South Nation Conservation permit, excavation, tank and bed installation, final inspection — and, on replacements, decommissioning the old tank so it isn't a sinkhole waiting to happen. One written price, one crew, across Cornwall, SD&G and Prescott-Russell.
- Conventional, filter bed & advanced treatment systems
- Soil testing & percolation evaluation
- System SNC permit application
- Old tank removal & decommissioning
- Leaching bed & distribution box construction
- OBC Part 8 final inspection & documentation
What a Septic System Installation Looks Like
From the first site visit to the inspector's sign-off, most installs in the counties take two to four weeks — with only two or three days of actual digging.
Site Visit & Soil Test
We walk the lot, dig test pits, check percolation and water table, and count bedrooms and fixtures. On a replacement we inspect the old system to plan the removal.
Permit
We size the tank and bed for your household and soil, draw the layout, and file the sewage system permit with South Nation Conservation. You get the written flat-rate price at this stage.
Excavation & Install
Old tank pumped, crushed and backfilled if there is one. New tank set, lines run, bed built with inspected stone and pipe. Usually 1–3 days on site.
Inspection & Handover
SNC inspects before backfill, we restore the grade, and you receive the permit closure, as-built drawing and a maintenance schedule — the paperwork a future buyer will ask for.
The Right Septic System for SD&G Soil — Not a Template
Heavy clay around Lancaster and Williamstown. High water tables along the river in Glen Walter and Summerstown. Shallow bedrock north of Alexandria. A system that works on one concession road fails on the next, and the Ontario Building Code decides what's allowed on your soil — not the installer's preference.
That's why we test first and quote second. Here are the three system types we install most, and when each one makes sense.
Conventional Leaching Bed
Tank plus a gravel-and-pipe bed. Lowest cost, works where soil drains well and there's room — most Cornwall-area lots with sandy loam.
Raised / Filter Bed
Imported sand builds the bed above grade. The answer for clay, high water tables and smaller lots — common in Glengarry's river properties.
Advanced Treatment Unit
Secondary treatment that lets the bed be much smaller. For tight lots, lakefront setbacks, or when a conventional bed simply won't fit under OBC rules.
Planning a Build or Replacing a Failed System?
Book a site visit and you'll have a soil assessment, a system recommendation and a written flat-rate price — before you commit to anything.
What Actually Drives the Cost of a Septic Installation in Cornwall
Quotes for the same house can be thousands apart, and it's rarely because one contractor is "ripping you off." It's because the lot decides most of the price. Here's what moves the number, so you can read any quote — ours included — with open eyes.
Our quotes break every one of these out as a line item, with the SNC permit fee included. The number you sign is the number you pay.
Soil & water table
Clay or a high water table means a raised bed with imported sand — the single biggest cost swing. Sandy loam keeps it conventional and cheaper.
Bedrooms, not people
The Ontario Building Code sizes the system by bedrooms and fixtures. A 5-bedroom farmhouse with two empty-nesters still needs a 5-bedroom bed.
Lot size & setbacks
Distance to the well, property lines, the river or a lake dictates where the bed can go. Tight lots push you toward an advanced treatment unit.
Decommissioning the old system
On a replacement, the old tank must be pumped, crushed or removed, and backfilled. Steel tanks are quick; big concrete ones take a day.
Access & restoration
A long laneway, mature trees or a finished landscape means more care getting equipment in and more work putting the yard back.
Permit & inspection
South Nation Conservation charges a permit fee for every new or replacement system in Cornwall and the counties. We include it; some quotes leave it for you to discover.
System type
A conventional bed is the baseline; a filter bed adds sand and labour; an advanced treatment unit adds equipment and an annual service contract.
Season & ground conditions
Frozen ground in January or a wet spring in the clay belt slows excavation. Late spring through fall is fastest and usually cheapest.
Septic Installation in Cornwall — Common Questions
How much does a septic installation cost in Cornwall, Ontario?
A conventional system on good soil is the least expensive; a raised filter bed on clay or an advanced treatment unit on a tight lot costs considerably more. The lot, the bedroom count and whether an old system must be removed drive the price. We give a written flat-rate quote after the soil test, with the SNC permit fee included.
Do I need a permit to install a septic system in Cornwall or SD&G?
Yes. Every new or replacement sewage system needs a permit under Part 8 of the Ontario Building Code, issued by South Nation Conservation for the City of Cornwall and the surrounding townships. We prepare file the application and book the inspections — you don't deal with the permit office at all.
How long does a new septic system installation take?
Two to four weeks from site visit to final inspection, most of it waiting on permit approval. The actual excavation and install is one to three days. On replacements we schedule so you're without a working system for as little time as possible — usually under a day.
Can you install a septic system on clay soil or near the river?
Yes — that's most of Glengarry and the St. Lawrence shoreline. Clay and high water tables call for a raised filter bed built with imported sand; tight waterfront lots with strict setbacks usually need an advanced treatment unit. The soil test tells us which is approved by SNC before we dig.
What happens to the old septic tank when you replace the system?
It's pumped dry, then either removed or crushed in place and backfilled with compacted fill so it can never collapse under a lawn tractor or a child. Steel tanks come out; large concrete tanks are usually broken and buried. Decommissioning is included in every replacement quote.
Book Septic Service in Cornwall
Pumping, cleaning, inspection, repair or a new system — leave your details and we'll call back with a flat-rate price.
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Backups, alarms and overflowing tanks don't wait. Our emergency line is open 24/7.
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What Customers Say About Our Septic Installation Work
New builds, failed-bed replacements and tricky lots — installed for homeowners and builders across Cornwall, SD&G and Prescott-Russell.
Building on a lot outside Martintown and the builder said "find a septic installer, that's on you." Searched "septic installation near me", they came out, did the test pits and had the SNC permit back in under three weeks. System was in and inspected before the framing was done.
Jason D.
Martintown · Sep 2026
Forty-year-old bed finally failed and we were pumping every three weeks just to flush. Two quotes said "conventional," theirs said raised bed because of our clay — and explained why the cheaper ones would fail inspection. Right call. Old tank crushed, new system in, yard graded, done in three days.
Hélène M.
Lancaster · Aug 2026
Waterfront lot near Summerstown with setbacks that made a normal bed impossible. They chose an advanced treatment unit that fit, handled every back-and-forth with South Nation, and the inspector passed it first visit. Nobody else we called would even quote the job.
Peter W.
Summerstown · Jul 2026
Bought a farmhouse outside Avonmore and the inspection flagged the system as end-of-life. Googled "septic system installation near me" the day after closing. Their quote listed every line item including the permit — the other two left the permit out and would've surprised us later. Clean job, honest people.
Sarah R.
Avonmore · Jun 2026
I'm a GC and I've used them on four rural builds between Cornwall and Casselman now. They coordinate with my schedule and I've never had an SNC inspection fail. That's the only septic installer I hand to my clients.
Mike B. — Contractor
Casselman · May 2026
Added a basement apartment and learned the old 3-bedroom system wasn't legal for a 5-bedroom house. They sized a new bed, pulled the permit, and we were without service for maybe six hours during the switchover. Left us the as-built drawing and a pump-out schedule — professional septic installation start to finish.
Luc T.
Long Sault · Apr 2026
Septic Services Across Cornwall, SD&G & Prescott-Russell
Based at 17171 Cornwall Centre Rd in South Stormont — same flat-rate pricing whether you're inside city limits or at the end of a concession road.
Our Office
17171 Cornwall Centre Rd, Unit 7
South Stormont, ON K0C 1P0
Cornwall & Glengarry
Stormont & Dundas
Prescott-Russell
Don't see your township? (613) 702-1122 — we cover all of SD&G and Prescott-Russell.