Almost every page you can find about grey water costs is priced in US dollars, for a US regulatory regime, by a company that wants to sell you a filter. That is not much use if you are standing on a lot near Bobcaygeon trying to work out whether a grey water system saves you money.
So here are Ontario numbers, in Canadian dollars, for what a permitted Class 2 grey water system actually costs to put in the ground — including the parts people forget to budget for, and an honest comparison against the full septic you might be trying to avoid.
One thing to settle before the numbers, because it changes the entire calculation: a grey water system is not a cheaper septic. It handles sink, shower, and laundry water only. The toilet still has to go somewhere, and that somewhere is either a composting toilet or a full Class 4 system. Budget for both halves or the number will be wrong. Our grey water systems at Ontario cottages guide covers when the setup is legal in the first place.
The Short Answer
| What you are buying | Installed cost |
|---|---|
| Class 2 grey water system, simple | $3,000–$8,000 |
| Class 2 grey water system, complex (lake setbacks, imported fill, raised pit) | $8,000–$15,000 |
| Composting toilet (Class 1), toilet only | $1,500–$5,000 |
| Class 1 + Class 2 combo, all in | $5,000–$15,000 |
| Grey water tie-in for a single sink, to an existing system | $1,500–$4,000 |
| Remediating an unpermitted grey water arrangement you inherited | $5,000–$15,000 |
The spread between simple and complex is not padding. It is the difference between a flat lot with decent sand and a shoreline lot where the pit has to be raised, the fill has to be trucked in, and the designer has to argue the setbacks. Which one you have is not something you get to pick.
Where the Money Actually Goes
The install price is the visible part. On a Class 2, the soft costs are a bigger share of the total than most people expect, because the paperwork does not get much cheaper just because the system is small.
| Line item | Typical cost | Notes |
|---|---|---|
| Site evaluation and perc test | $500–$1,500 | Skipped only if valid recent results exist |
| Soil profile / deep test pit | $500–$1,000 | Sometimes bundled with the perc test |
| Sewage system designer | $1,500–$3,500 | Required. A Class 2 still needs a stamped design |
| Septic permit, City of Kawartha Lakes | $433 | The City’s published 2026 fee for a Class 2. A Class 4 permit is $975 |
| Excavation, settling chamber, leaching pit, backfill | The balance | This is what varies most by site |
Add those up and you notice something: on a simple $3,000–$8,000 job, the design and permitting can come close to half the total. That is the most surprising thing about Class 2 pricing, and it is why a grey water pit for a bunkie sometimes costs nearly as much as one for a whole cottage. The hole is small. The paperwork is not.
It is also why the tie-in option — running a single new fixture into a system that already exists and already has capacity — comes in at $1,500–$4,000. You are buying pipe and labour, not a second regulatory process.
The Comparison That Actually Matters
This is where most of the internet gets it wrong, including plenty of pages that ought to know better. People compare a grey water system against the most expensive septic they can imagine, and the saving looks enormous.
Done honestly:
| System | Installed cost |
|---|---|
| Class 1 + Class 2 (composting toilet + grey water) | $5,000–$15,000 |
| Class 4 conventional, tank and tile bed, good soil | $15,000–$22,000 |
| Class 4 raised bed / mound | $25,000–$45,000 |
| Class 4 with tertiary (Level IV) treatment | $28,000–$45,000 |
Against a conventional Class 4 on a decent lot, the grey water route saves somewhere in the range of $7,000 to $15,000. That is real money, but it is not the dramatic saving the off-grid blogs imply, and you are accepting a composting toilet to get it.
Against a raised bed or a tertiary unit — which is what you get quoted when the soil is bad, the water table is high, or the lot is tight to the lake — the gap widens to $20,000 or more. And that is precisely the situation where a Class 2 is most likely to be the right answer anyway, because the same site conditions that make a Class 4 expensive are the ones that make a small system attractive. If a perc test has already failed on your lot, the comparison shifts hard in grey water’s favour.
The honest framing: grey water saves the most exactly when a full septic costs the most. On an easy lot with good soil, the saving is real but modest, and you should weigh it against never having to think about a composting toilet again.
What It Costs to Run
Ongoing cost is the part of the pitch that holds up best.
| Ongoing item | Cost |
|---|---|
| Class 2 pump-out | $200–$400 |
| Total maintenance over 25 years | $2,000–$4,000 |
| Composting toilet servicing | Varies by unit; budget an annual visit |
A Class 2 has less to go wrong than a Class 4 and less volume moving through it. Solids still accumulate in the settling chamber and still have to come out every five to ten years. Grease and soap residue still blind the leaching pit over time — the pit is the part with a finite life, typically 15 to 25 years before it needs rehabilitation or replacement, against 30 to 50 years for the chamber itself.
Budget for the pit to be redone once in the life of the cottage. People who do not, and who have run kitchen water through it for two decades, tend to find out during a property sale.
The Cost Nobody Budgets For
The most expensive grey water system in Ontario is the one that is already in the ground and was never permitted.
Older cottages around the Kawarthas are full of informal arrangements — a kitchen sink running to a stone pit, laundry water going to a dry well of unknown vintage, an outdoor shower draining onto the grass. Most predate current code, most were never recorded with the building department, and most work fine right up until someone official looks at them.
The trigger is almost always a sale, a refinance, or a renovation that needs a permit. At that point the remediation is a permitted Class 2 system, or an extension of the existing Class 4 to take the extra fixtures, and it runs $5,000–$15,000 on a timeline you do not control. It is the same money as doing it properly, spent under deadline pressure, usually while a closing date moves.
If you are buying a cottage with any drain you cannot fully account for, that is a number worth knowing before you waive conditions, not after. Kawartha Lakes has its own layer of rules on top of the provincial ones, and Conservation Authority involvement near the water can add both time and cost.
Is It Worth It?
A Class 2 grey water system is worth the money in three situations, and is a poor deal outside them.
It is worth it when a full septic is expensive on your lot. Bad soil, high water table, bedrock, or shoreline setbacks that push you toward a raised bed or tertiary unit. Saving $20,000 is worth accepting a composting toilet for a lot of people.
It is worth it for genuinely low-use buildings. A bunkie, a sauna, a hunt camp, an outbuilding with a sink. Look hard at the tie-in option first — if the main system has capacity, $1,500–$4,000 beats $3,000–$8,000.
It is worth it for buildings that are not dwelling units. A bunkie without a kitchen, a sauna, a workshop with a sink. This is also where the tiny home question gets complicated, and it is worth reading the next section before you budget anything.
It is not worth it for a normal cottage or house with a flush toilet you intend to keep. In that scenario a Class 2 is not an alternative to anything. It is an additional system alongside the Class 4 you still need, and the money is better spent on the septic.
There is also no meaningful rebate money for this in most of Ontario — our guide to septic grants and rebates covers what does and does not exist.
The Rule Change That Breaks the Old Math
Everything above assumes the composting toilet plus grey water route is available to you. Since 1 January 2025, for a lot of people, it is not.
The 2024 Building Code removed the composting toilet option from Article 9.31.4.1. A dwelling unit with a water distribution system now has to have a water closet — a flush toilet. The old wording allowed “a water closet or a drainless composting toilet.” The new wording does not.
What that means for a budget:
- New build, dwelling unit, running water: the Class 1 + Class 2 combo is off the table. You are pricing a Class 4, so the honest number is $15,000–$22,000 on good soil and more on difficult ground. Do not budget $5,000–$15,000 for a system you cannot get permitted.
- Existing setup: unchanged. The rule is not retroactive, and an existing composting toilet with a permitted Class 2 stays legal.
- Not a dwelling unit — a bunkie without cooking and sleeping facilities, an outbuilding, a sauna: arguably outside the article, but building officials read this differently and it is a question for your inspector before you spend anything.
There is a related honesty point that comes from building officials rather than from contractors: where a Class 2 needs a lot of imported fill, the savings often evaporate. On a tight or poor-soil site the volume of material a grey water pit needs can approach what a Class 4 bed needs, and a composting toilet is not cheap either. There are documented cases of the combo costing more than the Class 4 it was meant to replace. If someone quotes you a grey water system as the obvious budget option, ask what the fill and access cost, and get the Class 4 number for comparison.
Frequently Asked Questions
How much does a grey water system cost in Ontario?
A permitted Class 2 grey water system runs $3,000 to $8,000 installed for a straightforward site, and $8,000 to $15,000 where lake setbacks, imported fill, or a raised pit are involved. Add $1,500 to $5,000 for a composting toilet if you are using grey water in place of a full septic, which brings a typical combined build to $5,000 to $15,000.
Is a grey water system cheaper than a septic system?
Where it is still allowed, yes, but by less than most people assume. A Class 1 and Class 2 combination runs $5,000 to $15,000 against $15,000 to $22,000 for a conventional Class 4 system on good soil. The saving grows to $20,000 or more when the alternative is a raised bed or tertiary system on difficult ground. On sites needing a lot of imported fill the saving can disappear entirely. And since 1 January 2025 a new dwelling unit with running water has to have a flush toilet, which removes the option altogether for most new builds.
Can I still use a composting toilet instead of a septic system in Ontario?
Not for a new dwelling unit with a water distribution system. The 2024 Building Code, in force since 1 January 2025, requires a water closet in that situation and no longer accepts a drainless composting toilet as a substitute. Existing installations are not affected, and buildings that are not dwelling units may be a different case — ask your local building official before committing to a design.
Do I need a permit for a grey water system in Ontario?
Yes. A Class 2 system is a permitted sewage system under the Ontario Building Code, and the design has to be prepared by a licensed sewage system designer. In the City of Kawartha Lakes the 2026 permit fee is $433, and the permit comes from the City’s Building and Septic Division, not the health unit. There is no lot remote enough for the permit requirement to stop applying.
Why does the permit and design cost so much relative to the system?
Because the regulatory process does not scale down with the size of the hole. A designer still has to evaluate the site, confirm setbacks, and produce stamped drawings whether the system handles 300 litres a day or 3,000. On a simple Class 2 install, design and permitting can approach half the total cost.
How much does it cost to pump a grey water system?
A Class 2 pump-out runs $200 to $400, and most systems need one every five to ten years rather than every three to five. Over a 25 year period, total maintenance typically lands between $2,000 and $4,000.
What does it cost to fix an unpermitted grey water pit?
Bringing an informal arrangement into compliance generally costs $5,000 to $15,000, depending on whether the fix is a new permitted Class 2 system or an extension of the existing septic. This most often surfaces at a property sale, refinance, or renovation, which is the worst time to be discovering it.
Getting a Real Number for Your Lot
Every range on this page is a range because the site decides the price. Soil, slope, water table, distance to the well and the lake, and whether a truck can get where the pit needs to go are what move a Class 2 from $3,000 to $15,000.
The design is stamped by a licensed sewage system designer, not by us. What we do is coordinate that design and the permit, subcontract the excavation, and book the inspections — and we pump, inspect, and assess grey water systems that are already in the ground, including the informal ones nobody has paperwork for.
If you have an old arrangement you are unsure about, or a build where grey water might be the right call, the useful first step is someone looking at the actual lot. We serve Kawartha Lakes — Lindsay, Bobcaygeon, Fenelon Falls, Coboconk, and the rural and waterfront properties between them — with no travel surcharge anywhere in the city.
Call (705) 702-5526 or book online. If what you actually need is a full system, our septic system installation page covers that side, and the replacement cost guide has the Class 4 numbers in detail.