Open any Ontario septic permit and somewhere on the document you’ll see a number: Class 1, 2, 3, 4, or 5. That number decides what kind of system you have, what you’re allowed to install, what’s grandfathered, and what a buyer’s lawyer is going to ask about during a sale.
Most Kawartha Lakes homeowners have a Class 4 system and have never thought about it. Most cottage owners have either a Class 4 or a Class 5, and the difference between those two is the difference between a $400 pump every few years and a $400 pump several times a season.
This guide walks through all five classes in plain English: what each one is, when you’d have it, what it costs to maintain, and what the class number means if you’re buying, selling, or building.
The Quick Answer: All Five Classes at a Glance
| Class | What it is | Common where | Treats sewage? | Common in Kawartha Lakes? |
|---|---|---|---|---|
| Class 1 | Earth pit privy, composting toilet, chemical toilet | Remote cottages, outhouses, off-grid | No (dry/composting) | Older cottages, bunkies |
| Class 2 | Greywater system (no toilet waste) | Small cottages with separate composting toilet | Greywater only | Some lakefront cottages |
| Class 3 | Cesspool | Pre-1970s installations | Partial, no longer accepted | Rare, grandfathered only |
| Class 4 | Conventional septic (tank + leaching bed) | The vast majority of rural homes | Yes | ~95% of properties |
| Class 5 | Holding tank (sealed, no leaching bed) | Tiny lots, bad soil, lakefront with no setback room | No, just stores; pumped out | Lakefront cottages with site constraints |
Each class is defined under Part 8 of the Ontario Building Code, which is the regulation that governs all on-site sewage systems in the province.
Class 1: The Earth Pit Privy and Composting Toilet
A Class 1 system is the simplest installation Ontario recognizes. It includes:
- Earth pit privies, what most people would call an outhouse
- Composting toilets, modern self-contained units that compost waste in place
- Chemical toilets, portable units with chemical breakdown
These systems handle only human waste, not greywater. There’s no tank, no leaching bed, no plumbing. Capacity is limited and use is typically seasonal or low-frequency.
You’ll find Class 1 systems on remote cottages, hunting camps, off-grid bunkies, and older shoreline cabins where running water either doesn’t exist or feeds only a sink that drains separately. They’re also common on rental cottages used as guest sleeping quarters, where adding a full Class 4 system would cost more than the building.
The catch most people miss: as soon as you add a flush toilet to a Class 1 property, you’ve changed the system class. That triggers permits, and depending on lot conditions, may require a perc test and a full Class 4 installation. We’ve watched bunkie expansions turn into $30,000 septic projects because nobody checked first.
Maintenance: depends on type. Earth pit privies require periodic relocation or pump-out. Composting toilets need annual emptying and material rotation. Chemical toilets need regular pump-out and chemical replacement.
Class 2: Greywater-Only Systems
A Class 2 system handles only greywater, wastewater from sinks, showers, washing machines, and dishwashers, but not toilet waste.
These pair with a Class 1 toilet (composting, privy, or similar) on properties that want indoor running water without the cost or footprint of a full Class 4 system. The greywater drains into a small leaching pit or shallow soakaway designed for the lower contaminant load.
You’ll see Class 2 most often on:
- Small cottages with composting toilets and full kitchens
- Off-grid builds where minimizing infrastructure is a priority
- Lakefront properties with severely limited septic setback options
The catch: a Class 2 system is not a backdoor to skipping a real septic. The moment you connect a flush toilet, the system reclassifies upward and the whole permit conversation changes. Some municipalities are also stricter than the OBC base requirement, particularly in source water protection areas.
Maintenance: the leaching pit requires monitoring and occasional rehabilitation. Grease and soap buildup is the most common failure mode.
Class 3: Cesspools (Why You Probably Don’t Have One)
A Class 3 cesspool is essentially a deep covered pit lined with stone or perforated concrete. Sewage flows in, solids accumulate, liquids leach into the surrounding soil through the porous walls. No proper treatment, no defined leaching bed.
Cesspools were common in rural Ontario before the 1970s. They are no longer permitted for new construction. If you have one, it’s grandfathered; meaning you can keep using the existing system, but you cannot expand or replace it with another cesspool. The replacement has to be a modern Class 4 system.
A homeowner near Lindsay we worked with two summers ago discovered her 1960s farmhouse was on a Class 3 system only when the buyer’s lawyer flagged it during a sale. The disclosure form said “septic system.” It was technically true, but the cesspool had been failing for years, contaminating groundwater, and the deal almost died over the cost of remediation. She paid for a full Class 4 install to close the sale.
If you suspect you have a cesspool:
- Look at the original property records and septic permit (or absence of one).
- Get a proper septic inspection, an inspector will identify a cesspool quickly.
- Don’t ignore it if you find one. Sales and refinances both surface them. Better to know on your timeline than the buyer’s.
Maintenance: cesspools cannot be properly maintained, only delayed. Pumping helps short-term but doesn’t address the structural issue. Plan for a full replacement.
Class 4: The Standard Septic System (What 95% of Homes Have)
A Class 4 system is what most people picture when they hear “septic”, and the full mechanics of how it works are covered in detail elsewhere. The short version, it includes:
- An underground septic tank (typically 750 to 2,000 gallons)
- An outlet baffle and effluent filter that prevent solids from leaving the tank (more on this in our effluent filter guide)
- A distribution system that routes effluent to the leaching bed
- A leaching bed (also called a drain field) where soil filters and disperses the partially treated effluent
The tank settles solids and floats grease. The leaching bed handles the actual treatment. The combination is regulated under OBC Part 8, sized to the number of bedrooms in the home, and designed based on percolation rate from a perc test.
Within Class 4, there are sub-categories based on bed type:
- Conventional / in-ground bed, standard, where soil and water table allow.
- Raised bed, imported fill creates an above-grade bed when native soil is too slow or shallow.
- Mound (Wisconsin-style) bed, pressurized distribution into an engineered mound, used on difficult sites.
- Filter bed (sand-lined), used where soil is too fast and additional filtration is needed.
- Tertiary treatment + smaller bed, advanced treatment units (Ecoflo, Waterloo Biofilter, aerobic units) treat effluent to a higher standard before a smaller bed.
All of these are still Class 4 systems for permit purposes. The variation is in the bed design, not the class.
Maintenance: routine pumping every 3 to 5 years (heavier for cottages with rentals or high seasonal use). Effluent filter cleaning at every pump. Inspection if records are missing. (Cost ranges in our pumping cost calculator.)
Lifespan: a well-maintained Class 4 system runs 25 to 40 years. The tank can outlast that; the leaching bed is usually the limiting factor.
Class 5: Holding Tanks (When You Have No Other Option)
A Class 5 system is a sealed tank with no leaching bed. Sewage goes in, sewage stays in, and a pump-out truck removes it on a schedule. There is no soil treatment component at all.
Class 5 is permitted only when conventional treatment isn’t possible. Common scenarios:
- Tiny lakefront lots where setback rules from the lake, well, and property lines leave no room for a leaching bed
- Bedrock too shallow to support any in-ground or raised bed
- Seasonal-only properties with very low total water use and serious site constraints
The tank is typically 1,000 to 3,500 gallons. Capacity dictates pump-out frequency, and pump-out frequency dictates ongoing cost. This is the key economic difference from Class 4.
Cost reality for cottage owners: a busy 1,500-gallon holding tank on a heavily-used lakefront cottage may need pumping every 1 to 4 weeks during the season. At $300 to $500 per pump, that adds up fast, easily $3,000 to $8,000+ per season for high-use properties. We’ve covered this comparison in detail in septic vs holding tank: what’s the difference.
If you’re buying a cottage advertised as having a “septic system,” read the documents carefully. Class 5 is a holding tank, not a real septic. The implications for cost, capacity during a busy weekend, and resale value are all materially different. (Our buying a cottage with a septic system guide flags this and other class-related red flags.)
Maintenance: scheduled pumping based on use. High-water alarm should be installed and working. Failure mode is overflow, and on a small lakefront lot, overflow becomes a regulatory and water quality emergency very quickly.
Why the Class Matters for Buyers and Sellers
The class number on a septic permit is one of the first things a buyer’s lawyer checks during due diligence. Each class carries different implications:
- Class 1 or 2 only: limits what you can do with the property without a major upgrade
- Class 3 (cesspool): a remediation expense waiting to happen; usually surfaces during sale
- Class 4: standard, expected for most rural properties; buyers want recent inspection and pumping records
- Class 5: changes the cost profile of ownership; high-use buyers may walk
Sellers who don’t know their own system class often get caught flat-footed when the question comes up at closing. The fix is simple: before you list, get a septic inspection and confirm the class on file. That document goes into the listing package, the buyer can review it during due diligence, and price negotiations stay focused on the real condition rather than uncertainty.
What Class You Need: How Soil and Lot Decide
If you’re building or replacing, the class isn’t really your choice. It’s determined by:
- Lot size and setbacks, wells, lakes, property lines, slope
- Soil percolation rate (from the perc test)
- Seasonal high water table depth
- Bedrock depth
- Water use intensity (number of bedrooms = sizing requirement)
A spacious lot with sandy loam, deep water table, and no rock will accept a conventional Class 4 with no fuss. A small lakefront lot with shallow bedrock and mediocre soil may push you toward a Class 4 with raised bed, a tertiary treatment system, or, in worst cases, a Class 5 holding tank.
The licensed sewage system designer who runs your perc test will tell you what the lot can support. That conversation should happen before you finalize a build budget or close on a property, see our broader septic system rules in Kawartha Lakes guide for more on the regional context.
Septic Class FAQ
My permit doesn’t list a class. What do I have? Most likely a Class 4. If your home was built in or after the 1970s and has a flush toilet, indoor plumbing, and a tank in the yard, it’s almost certainly Class 4. Confirm with an inspection if you’re not sure.
Can I upgrade from a Class 5 holding tank to a Class 4 septic? Sometimes. Depends on whether your lot can now support a leaching bed (lot size, setbacks, soil). The first step is a perc test and site evaluation. If the original Class 5 was installed because no Class 4 was possible, conditions probably haven’t changed. But site changes (well relocation, lot consolidation, vegetation clearing) sometimes open up new options.
Is a “Class 4 with tertiary treatment” the same as Class 4 conventional? Same class, different technology. Both fall under Class 4 in OBC Part 8. The tertiary unit treats effluent to a higher standard before a smaller leaching bed, useful on tight or sensitive sites.
Are aerobic treatment units a separate class? No. Aerobic treatment units (ATUs) are still Class 4 systems. The “class” refers to the regulatory category, not the treatment technology.
Does the class affect insurance rates? Sometimes indirectly. Insurers care more about age, condition, and maintenance history than the class itself, but a Class 5 holding tank may flag differently in some underwriting systems.
Can I have more than one class on a property? Yes. A cottage with an indoor flush toilet (Class 4) plus a separate bunkie with a composting toilet (Class 1) and a sink draining to a Class 2 greywater pit is a real configuration we see on larger lakefront properties.
The Class Is Just the Starting Point
Knowing your class number is useful, but it’s not the whole picture. A 30-year-old Class 4 with a failing leaching bed is in worse shape than a brand-new Class 5 holding tank with a smart-monitor alarm. What matters at sale, at insurance, at the moment something goes wrong, is the current condition of the system you have.
We service the Kawartha Lakes region, Lindsay, Bobcaygeon, Fenelon Falls, Coboconk, and surrounding rural and waterfront properties. We pump and inspect every class except Class 1 (no tank to pump) and Class 3 (which we’ll flag for replacement, not maintenance). If you don’t know what class you have, an inspection sorts it in one visit.
Need an inspection or scheduled pump? Call (705) 242-0330 or book online. Use the cost calculator for a 60-second estimate.