FREE TOOL
SEPTIC TANK SIZE CALCULATOR
Enter your bedrooms and how the property is used. Get the minimum tank size under Ontario Building Code Part 8, how often that tank should be pumped, and what a routine pump-out costs in Kawartha Lakes.
Enter your bedrooms and how the property is used. Get the minimum tank size under Ontario Building Code Part 8, how often that tank should be pumped, and what a routine pump-out costs in Kawartha Lakes.
Four questions. The result shows the code minimum, whether you should go a size up, and your pumping schedule.
Recommended: . The code sets a floor, not a target — a larger tank gives solids longer to settle and takes stress off the leaching bed.
Base rate for the nearest tank size. Refine it with access and property type →
Sizing is set by your licensed sewage system designer and confirmed by the City of Kawartha Lakes Building and Septic Division (705-324-9411) on the permit. This tool gives you the starting point, not the permit.
We measure the tank during a routine pump-out and write the size down for you.
Book a Pump-Out (705) 702-5526Part 8 of the Ontario Building Code sets the rules. Here is what the calculator is doing behind the numbers.
The Code sizes by bedrooms because occupants change and bedrooms do not. A 4-bedroom house needs at least a 4,000-litre tank whether two people or eight live in it.
The Code minimum is twice the daily design flow of the house (never under 3,600 L), so solids settle and bacteria get to work. Too small, and solids push straight out into the leaching bed — the part that costs the most to replace.
A garbage disposal, a hot tub, or extra laundry loads the tank harder than the bedroom count implies. The next tank size costs modestly more at install and pays back in bed life.
The Code sizes a private cottage by bedrooms, the same as a house. Seasonal use changes how often you pump, not the minimum tank. Adding bedrooms or converting to year-round use can trigger a City review.
Household size and use pattern set the interval: 4 to 5 years for a small year-round household or weekend cottage, down to 1 to 2 years for a vacation rental with constant turnover.
The licensed sewage system designer specifies the tank on the permit drawing, and the City of Kawartha Lakes Building and Septic Division approves it. We install what the stamped design says.
A 1, 2 or 3-bedroom home needs a minimum 3,600-litre (800-gallon) septic tank under Part 8 of the Ontario Building Code. Many installers in Kawartha Lakes recommend a 4,500-litre tank for a 3-bedroom house if it has a garbage disposal, hot tub, or other high-water fixtures, because the extra retention time protects the leaching bed.
Bedrooms. The Ontario Building Code counts any room that could be used as a bedroom, not current occupants, because a 4-bedroom house with two people in it today could have eight in it next year. A 4-bedroom home needs at least a 4,000-litre tank (in practice the 4,500-litre stock size) regardless of who lives there now.
It depends on the tank and the household. A year-round home with 1 to 2 people can usually go 4 to 5 years; 3 to 4 people, 3 to 4 years; 5 or more people, 2 to 3 years. A lightly used seasonal cottage runs 4 to 5 years, a heavily used summer cottage 2 to 3 years, and a vacation rental with high guest turnover 1 to 2 years. Every 3 to 5 years is the shorthand for most households.
Not under the Building Code. The daily design flow table sizes a private cottage by bedrooms exactly like a year-round house, so a 3-bedroom cottage needs the same 3,600-litre minimum. Seasonal use changes how often you pump, not the minimum tank size. Adding bedrooms or converting to year-round living can still trigger a City review of the existing system.
Check the original septic permit at the City of Kawartha Lakes Building and Septic Division (705-324-9411), which lists the tank size. If no records exist, we can measure the tank during a routine pump-out and write the size down for you.
Send your details and the result above comes with them. We call you back within 24 hours on business days.
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(705) 702-5526
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info@kawarthaseptic.ca