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 a 4,500-litre tank whether two people or eight live in it.
The tank has to hold at least two days of wastewater 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.
A genuinely seasonal cottage can qualify for reduced design flow. Convert it to a year-round home and the system must be sized for year-round use — usually with a permit.
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 a minimum 4,500-litre tank 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.
Sometimes. Ontario allows reduced daily design flows for genuinely seasonal properties, so a cottage used May through October can qualify for a smaller system than the same house occupied year-round. The catch is conversion: if the cottage becomes a year-round home, the system has to be sized for year-round use, and that usually needs a permit.
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