A composting toilet can take the toilet off your septic bill, but at an Ontario cottage it never takes the sinks and shower with it.
A composting toilet (or composting loo, if you grew up with the British term) turns human waste into a dry, soil-like material using air, carbon and time instead of water. On the right property, like an off-grid bunkie, a hunt camp or a water-access cottage on rock, it solves a real problem more cheaply than a full septic system.
What surprises most cottage owners shopping for one is everything around the toilet. Every drop of shower, sink and laundry water still needs somewhere legal to go, and since 1 January 2025 the Building Code has closed the composting toilet route for most new dwellings with running water.
This guide covers both halves: how they work, the types and brands sold in Canada, and what Ontario still requires.
The Quick Answer
| Question | Short answer |
|---|---|
| How does a composting toilet work? | Aerobic bacteria break waste down with bulking material (peat or coir), airflow from a vent stack, and evaporation. No water, no tank. |
| Main types | Self-contained, central (drum below the floor), urine-diverting. Each comes electric or non-electric, and a few are micro-flush. |
| Brands common in Canada | Sun-Mar and Envirolet (both Ontario-based), plus Separett, Nature’s Head and Air Head |
| Is it legal in Ontario? | Yes, as a Class 1 sewage system, but not as the only toilet in a new dwelling unit with running water (since 2025) |
| Do I still need a septic? | For grey water, yes: a permitted Class 2 or other approved system |
| Best fit | Bunkies, hunt camps, low-use seasonal cabins, boats |
| Poor fit | Rentals, busy family cottages, new year-round builds with plumbing |
How a Composting Toilet Works
A composting toilet is a dry toilet that manages waste on site. Waste drops into a chamber or drum where aerobic (oxygen-using) bacteria break it down into a stable, earthy material. Here’s how a compost toilet works, piece by piece.
Aerobic decomposition. The bacteria doing the work need oxygen. With air, waste breaks down into carbon dioxide, water vapour and a humus-like residue. Without air, it goes anaerobic, which is what a septic tank or a neglected pit does, and that’s where the rotten-egg smell comes from.
Moisture and carbon. Human waste is wet and high in nitrogen. The bacteria want something closer to a damp sponge, with plenty of carbon. That’s the job of bulking material, usually peat moss, coconut coir, or a manufacturer’s own mix. It soaks up excess liquid, adds carbon, and keeps air pockets open. Some units have a crank-turned drum or a mixing handle to fold it in.
Ventilation. Every composting toilet needs a vent stack running from the chamber up through the roof. Air is drawn in through the bowl and out the stack, so odour leaves the building instead of entering the room. Electric units add a small fan to keep that airflow constant. Non-electric units rely on a wider vent pipe and natural draft.
Evaporation. Most of what goes into a toilet is liquid. A composting unit has to get rid of it, mostly by evaporating it out the vent. Electric units often add a heating element to speed this up. This is why liquid load, not solids, is the usual limit on how many people a unit can serve.
Finished compost. Over weeks to months, the material shrinks and dries. It’s removed from a finishing tray or bin and, following the manufacturer’s instructions and local guidance, buried or disposed of away from wells and water. It shouldn’t go on food crops.
Urine Diversion vs Mixed Chambers
There are two design approaches.
A mixed chamber takes urine and solids together, then relies on bulking material, a fan and heat to handle the liquid. Sun-Mar’s drum units and Envirolet’s systems work this way.
A urine-diverting (or dry-separating) toilet has a split bowl. Urine runs forward into a bottle or a separate line, and solids drop into a dry chamber. Keeping the solids dry cuts odour and weight, and the units can be much smaller. The trade-off is emptying the urine bottle every day or two with regular use.
One Ontario-specific caution: if diverted urine, or any overflow, runs to a drain or soakaway instead of a container you empty, the toilet isn’t drainless anymore. Talk to the City before you plumb one that way (more on that below).
Types of Composting Toilets
The composting toilet system you choose comes down to where the chamber sits, whether urine is separated, and whether you have power.
| Type | How it’s set up | Power | Suits |
|---|---|---|---|
| Self-contained | Toilet and composting chamber in one unit on the bathroom floor | Electric or non-electric models | Cottages, bunkies, cabins with light to moderate use |
| Central (remote) | Ordinary-looking toilet upstairs; drum or tank in a basement or crawl space below the floor | Electric or non-electric | Busier cottages and year-round cabins with space below |
| Urine-diverting / dry-separating | Split bowl; urine to a bottle, solids to a small dry chamber | Usually a small 12-volt fan | Boats, small bunkies, tight spaces, solar setups |
| Waterless | No water connection at all | Any of the above | Most cottage and camp installs |
| Micro-flush | Small rinse of water per use into a central unit | Usually electric | Owners who want a flush-style bowl; check Code fit first |
Electric vs Non-Electric Units
Non-electric (passive) units use natural ventilation and a larger vent stack, sometimes with a urine-diverting bowl, to keep the chamber dry enough to work. They’re the simplest and cheapest option and the obvious choice for a bunkie or camp with no power. They’re more sensitive to overuse and humidity, and too much liquid without enough bulking material is the most common cause of odour complaints.
Electric units add a fan for constant ventilation and often a heater for evaporation. They handle heavier use more reliably and forgive the odd weekend when nobody added bulking material. The catch is a steady power draw, which matters at an off-grid property running on solar. Low-draw 12-volt fans are the middle ground.
Matching the Type to the Building
- Seasonal cottage: a self-contained or central unit sized for your peak summer crowd, not the average weekend.
- Bunkie: a compact self-contained or urine-diverting unit. Low use and no water keep it simple.
- Boat: a marine composting toilet, which is almost always urine-diverting with a 12-volt fan and a compact, sometimes hull-shaped base. Boat rules are separate from the Building Code and outside what we cover here.
- Year-round cabin: a central system with the drum in a heated space below the floor. Composting slows to a crawl in the cold, so an unheated crawl space in a Kawartha winter works against you.
Choosing a Composting Toilet in Canada
Before brand, settle four things:
- Capacity rating. Manufacturers rate units separately for residential (continuous) and seasonal or vacation use. Size for the busiest long weekend.
- Power. None, 12-volt, or a standard outlet. A heater-equipped unit draws far more than a fan-only one.
- Space and vent route. A central unit needs room below the floor. Every unit needs a vent path up through the roof.
- Drainless or not. Some systems are sold with an optional drain for excess liquid. In Ontario, that choice has permit consequences.
Brands You’ll See in Canada
Descriptions below are what each manufacturer says about its own products. We don’t sell or install toilets and haven’t tested these units.
| Brand | Based | What they make | Power | Capacity class |
|---|---|---|---|---|
| Sun-Mar | Stoney Creek, Ontario | Self-contained drum units (including the Excel) and Centrex central systems | Electric and non-electric (NE) versions | Small cottage up to heavy seasonal or moderate year-round |
| Envirolet | Oshawa, Ontario (Sancor Industries) | Self-contained and remote systems, waterless and low-water | Non-electric, 12-volt or AC | Cottage to household |
| Separett | Sweden | Urine-diverting toilets such as the Villa | AC/DC fan (small draw) | Cabin and small household |
| Nature’s Head | United States | Compact urine-diverting self-contained unit | 12-volt fan | RV, boat, tiny cabin |
| Air Head | United States (Maine) | Compact urine-separating unit, built for boats | 12-volt fan | Boat, RV, small cabin |
Sun-Mar Excel composting toilet. The Excel is Sun-Mar’s self-contained model built around a rotating drum. The electric Excel has a fan and heater. Sun-Mar rates it for 3 adults in residential use or 6 in seasonal use and says it was the first self-contained toilet certified by NSF. The Excel NE has no built-in electrical parts, uses a 4-inch vent, offers an optional 12-volt fan, and carries a lower rating (2 adults residential, 5 seasonal).
Envirolet composting toilet. Envirolet is made by Sancor Industries of Oshawa, Ontario. The line includes waterless self-contained units, remote systems with the chamber below the floor, and low-water flush versions, in non-electric, 12-volt and AC options.
Best For, by Use Case
We don’t rank brands. The right unit is the one that matches your building:
- Off-grid bunkie, no power: a non-electric self-contained unit or a urine-diverting toilet with a 12-volt fan on a small solar panel.
- Family cottage, busy summers, power available: an electric self-contained or central unit rated for your peak headcount.
- Year-round cabin: a central system in heated space, rated for residential (not seasonal) use.
- Boat or very tight space: a compact urine-diverting marine unit.
What About NSF/ANSI 41?
NSF/ANSI 41 is the North American performance standard for composting toilets. Certified units are tested for capacity, odour, and the quality of the finished material. Some manufacturers advertise it and some building officials look for it.
Ontario’s Building Code doesn’t list NSF/ANSI 41 as a referenced standard. A Building Code Commission ruling found that a micro-flush composting toilet certified to NSF 41 didn’t satisfy the Code’s standard for water closets. So certification is a good sign of a well-engineered unit, but not an automatic Code pass. Ask the City what it expects before you buy.
Composting Toilets Are Still a Class 1 Sewage System
Under the Ontario Building Code, a composting toilet system is a Class 1 sewage system, the same class as privies, chemical toilets and incinerating toilets. Our Ontario septic classes guide lays out all five.
On permits, the City of Kawartha Lakes says sewage system permits are not required for Class 1 systems, but Code standards still apply. That’s not the same as unregulated. The unit has to be drainless, installed and vented properly, and the finished material handled away from wells and water. If the toilet is part of a new building or renovation that needs a building permit, expect the building official to look at it as part of that file. When in doubt, email the City’s septic permits office before you buy; it’s a short conversation. For how the sewage permit process works on the Class 2 side, see our permit guide.
If your plans lean even simpler, an outhouse is also a Class 1 system, with its own setback rules, covered in our guide to whether outhouses are still legal in Ontario.
You Still Need a System for Grey Water
This is the part that trips people up most, and it was true long before the 2025 change. A composting toilet removes blackwater (toilet waste) from your plumbing, but showers, sinks and laundry still produce grey water. Ontario requires that grey water to go to an approved system, usually a permitted Class 2, not a pipe out the wall.
A Class 2 isn’t small, either. The Code caps it at 1,000 litres a day of design flow, calculated from your fixtures, and a fully plumbed cottage with pressurized water can go over that cap on fixture count alone. Our grey water pit guide walks through the math, and our guide to grey water systems at Ontario cottages covers when one is allowed at all.
One thing inspectors do find: a composting toilet with an overflow drain is discharging human waste. That makes it blackwater, which needs a Class 3, 4 or 5 system. The Code’s wording was always drainless.
What Changed on 1 January 2025
Most of what’s written online about composting toilets in Ontario predates this.
The 2012 Building Code required a dwelling unit with a water distribution system to have “a water closet or a drainless composting toilet.” The 2024 Building Code, in force since 1 January 2025, dropped the second option. Article 9.31.4.1 now requires a kitchen sink, lavatory, bathtub or shower, and water closet in every dwelling unit where a water distribution system is available.
In practice: if you’re building a new dwelling unit with running water, a composting toilet no longer satisfies the Code. You need a flush toilet, which means a Class 4 septic or, in narrow cases, a Class 5 holding tank.
What it doesn’t mean:
- It isn’t retroactive. An existing composting toilet with a permitted grey water system alongside it stays legal.
- It may not reach buildings that aren’t dwelling units. A bunkie with no cooking facilities or a hunt camp is arguably outside the article, but building officials read this differently. Treat it as a conversation with your inspector.
- It doesn’t reach buildings with no water distribution system. The trigger is running water. A remote camp with hauled water is a different case.
Where Composting Toilets Make the Most Sense
| Situation | Fit |
|---|---|
| Off-grid bunkie or sleeping cabin, no plumbing otherwise | Strong fit |
| Seasonal camp with minimal water use | Strong fit |
| Hunt camp or remote cabin used a few weekends a year | Strong fit |
| Water-access or rock-bound lot where a leaching bed is hard to build | Worth exploring, alongside a Class 2 for grey water |
| Full year-round cottage with normal bathroom expectations | Weak fit, and for a new build with running water, no longer permitted |
| Rental or Airbnb property | Poor fit; guests handle maintenance inconsistently |
The properties where composting toilets work best share one thing: low, predictable use by people who know the routine. On Canadian Shield lots up around Coboconk and Norland, where shallow rock makes a conventional bed expensive, the appeal is obvious. Just remember the grey water side still needs soil, or imported fill, of its own.
Emptying and Maintenance: What It’s Really Like
A well-run unit needs:
- Bulking material added after each use or on a schedule, depending on the model
- Periodic mixing or drum turning to keep the process aerobic
- Emptying the finished compost every few weeks to a few months, depending on unit size and use (urine bottles on diverting units, far more often)
- Disposal of finished material per the manufacturer and local guidance, away from wells, water and vegetable gardens
- Occasional fan and vent checks on electric units
None of this is hard, but it’s hands-on in a way flush toilets aren’t. Owners who do well treat it like checking firewood or propane, a regular cottage chore. Rentals struggle because guests rarely follow the routine and are more likely to overload the unit or skip the bulking material.
Do Composting Toilets Smell?
A properly maintained, properly vented composting toilet shouldn’t smell noticeably worse than a normal bathroom. Aerobic breakdown doesn’t produce the sulphur-heavy odour anaerobic breakdown does, and the vent pulls air down through the bowl and out the roof.
Problems show up when the balance is off: too much liquid, too little bulking material, poor ventilation, or a bin past its emptying interval. A typical pattern: a new unit goes into a bunkie, it smells all season, and the owner blames the toilet. The cause turns out to be a fan that was never wired in, or a vent run with too many bends and too little height above the roof. The unit usually isn’t the problem. The installation is.
Cost Reality
| Item | Typical range |
|---|---|
| Self-contained unit | $1,500–$5,000 |
| Central composting system (larger household) | $3,000–$8,000 |
| Installation and venting | $500–$2,000 |
| Grey water system (still required) | Varies; see our grey water cost guide |
| Annual bulking material and supplies | $50–$150 |
Compare that with a conventional Class 4 system at $15,000 to $30,000 or more and the appeal for a low-use camp is clear. But the grey water side needs its own budget, so the total isn’t as cheap as the toilet price suggests. Call (705) 702-5526 and we’ll walk through your grey water side before you buy anything.
Off-Grid Bunkies and Sleeping Cabins
A composting toilet is still a natural fit for a bunkie that was never meant to carry full plumbing, and it’s the corner of this topic the 2025 change is least likely to have closed. A bunkie that isn’t a dwelling unit sits outside Article 9.31.4.1 on most readings, but confirm that with your building official first.
Adding a composting unit to a bunkie avoids tying into your main septic and sidesteps the capacity questions that come with adding fixtures. Our bunkie septic rules guide covers what changes once a sink goes in, and our tiny home septic guide covers small builds with any plumbing at all.
When to Call a Professional Instead of DIYing It
Installing a simple self-contained unit is within reach for a handy owner. DIY stops making sense at the siting and grey water side: distances to wells and the shoreline, designing the Class 2, and getting the vent run right. Get those wrong and you’re facing a compliance problem, a well contamination risk, or the odour issues above.
Frequently Asked Questions
Is a composting toilet legal in Ontario?
Yes. It’s a Class 1 sewage system under the Building Code. Since 1 January 2025 it can’t be the only toilet in a new dwelling unit with running water, but existing installations stay legal and non-dwelling buildings may still qualify.
Do I need a permit to add a composting toilet?
The City of Kawartha Lakes says Class 1 systems don’t need a sewage system permit, though Code standards still apply. The grey water system for your sinks and shower does need a permit, and a building permit for the structure may bring the toilet into review.
What is the best composting toilet in Canada?
There isn’t one best unit. Match the type to the building: a non-electric self-contained or urine-diverting unit for an off-grid bunkie, an electric self-contained or central unit for a busy cottage, and a central system in heated space for year-round use.
Can I use a composting toilet in a year-round home?
A new dwelling with running water now needs a flush toilet. In an existing home it’s workable, but the daily routine is a bigger commitment than cottage weekends.
Does a composting toilet replace my septic tank?
No. It replaces the toilet’s blackwater only. A septic system, or a permitted grey water system, still handles everything else.
How often does a composting toilet need emptying?
It depends on unit size and use: every few weeks for a small unit under heavy use, to a few months for a larger central system under light use. Urine bottles on diverting units need emptying every day or two.
Can I add a composting toilet to a cottage that already has a septic system?
Yes, and some owners do it to take load off an aging or marginal system. You still maintain the existing tank and bed, but they handle less volume.
Will a composting toilet reduce my well demand?
Yes. Toilets are typically a household’s biggest single water use, so removing one cuts well pumping noticeably.
Considering One for Your Kawartha Lakes Property?
We help property owners across Kawartha Lakes, Fenelon Falls, Coboconk and Bobcaygeon work out whether a composting toilet and grey water setup makes sense for a bunkie, camp or full cottage. We handle the septic side even when the toilet itself is someone else’s install.
Weighing a composting toilet against a full system? Call (705) 702-5526 or book online. Use the cost calculator for a 60-second estimate.