Making the right choice for your property’s septic system is one of the most important infrastructure decisions you’ll face. It’s not just about compliance, it’s a long-term investment in your home’s functionality, your property’s value, and your peace of mind. Get it right, and you’ll have a reliable system for decades. Get it wrong, and you could face costly failures, environmental issues, and significant stress.
Since 1966, Orangeville Precast has helped thousands of Ontario homeowners and contractors navigate this process. We’ve seen firsthand how a well-chosen concrete septic tank becomes a foundational asset. This guide distils our decades of experience into a clear framework to help you make a confident, informed decision that lasts.
Understanding Septic Tank Sizing: The Ontario Building Code Explained
The first and most critical step is determining the correct tank size. In Ontario, this isn’t a guessing game, it’s governed by the Ontario Building Code (OBC), which ensures systems are designed to handle a property’s specific needs.
It’s About Bedrooms, Not Bathrooms: OBC Daily Flow (Q) Calculations
A common misconception is that tank size is based on the number of bathrooms. The OBC, however, focuses on the maximum potential occupancy, which is best estimated by the number of bedrooms. The calculation revolves around determining your home’s daily design sewage flow, or ‘Q’.
Here’s a simplified breakdown of how it works:
- Base Calculation: The OBC assigns a daily flow rate based on the number of bedrooms in a home.
- Fixture Units: Additional water-using fixtures beyond a basic setup can increase your daily flow calculation.
- Living Area: The total finished living area of your home is also a factor.
The regulations (OBC Part 8) require that your septic tank’s minimum working capacity must be at least twice the daily sewage flow (2Q) for most residential systems. If you install a garburator, that requirement increases to three times the daily flow (3Q).
Example Sizing for a Typical Ontario Home:
|
Number of Bedrooms |
Typical Daily Flow (Q) |
Minimum Required Tank Size (2Q) |
|
1 to 2 |
1,100 Litres |
2,200 Litres |
|
3 |
1,600 Litres |
3,200 Litres |
|
4 |
2,000 Litres |
4,000 Litres |
|
5 |
2,500 Litres |
5,000 Litres |
Note: These are estimates. A certified professional must perform an official calculation for your permit.
Beyond the Numbers: Factors Influencing Your Ideal Size
While the OBC provides the minimum standard, several other factors should influence your decision:
- Property Usage: A cottage used only on summer weekends has different demands than a year-round family home. If you plan to convert a seasonal property to full-time use, it’s crucial to size the system for that future scenario.
- Water Habits: Do you have a large family, a hot tub, or high-efficiency appliances? Higher water usage means your tank works harder. It’s always wise to size up slightly to create a buffer.
- Future-Proofing: Planning an addition or expecting your family to grow? Installing a larger tank now is far more cost-effective than replacing an undersized system later. Think of it as an investment in your property’s future.
Making the right sizing decision is fundamental. If you’re unsure, our team can help you understand the factors that apply to your specific property.
Septic Tank Materials Compared: Concrete vs. Plastic vs. Fibreglass
Once you know the size, the next critical choice is the material. The three main options on the market are concrete, plastic (polyethylene), and fibreglass. While each has its place, they are not created equal, especially when dealing with Ontario’s demanding climate and soil conditions.
The Big Three: A Technical Deep Dive
|
Feature |
Precast Concrete |
Plastic (Polyethylene) |
Fibreglass |
|
Lifespan |
40 to 50+ years |
30 to 40 years |
30 to 40 years |
|
Durability |
Extremely high. Resists damage from soil pressure, frost heave, and vehicle traffic. Not buoyant. |
Moderate. Can be damaged by sharp objects during install. Prone to deformation or flotation in high water tables. |
High. Strong and corrosion-resistant, but can be brittle and prone to cracking under point-load stress. |
|
Installation |
Requires heavy machinery due to weight, ensuring stable placement. |
Lightweight and easier to install in remote or difficult-to-access locations. Requires careful backfilling. |
Lighter than concrete but requires careful handling to prevent damage. |
|
Cost |
Lower initial cost, and lowest lifetime cost due to exceptional longevity. |
Higher initial cost, but may require replacement sooner. Susceptible to damage. |
Higher initial cost, comparable to or more than concrete. |
|
Environmental |
Made from natural, inert materials. Structurally sound, preventing leaks that could contaminate groundwater. |
Petroleum-based product. Lighter weight means a smaller transport carbon footprint. |
Petroleum-based product. Susceptible to damage that can lead to leaks. |
|
Compliance |
Consistently meets and exceeds CAN/CSA-B66 standards for structural integrity. |
Must meet standards, but susceptible to deformation under load. |
Must meet standards, but can be prone to cracking. |
Ontario’s Climate & Soil: Which Material Stands Strongest?
This is where the choice becomes clear for most Ontario properties. Our region presents unique challenges that heavily favour the inherent strengths of precast concrete.
- Frost Heave: The freezing and thawing of Ontario soil exerts immense pressure. Concrete’s massive weight and structural rigidity provide superior resistance to this movement, preventing shifts that can damage pipes and compromise the system.
- High Water Tables & Clay Soils: In areas with heavy clay or high water tables, lightweight plastic and fibreglass tanks can literally float out of the ground if not installed perfectly and anchored correctly. Concrete’s sheer weight makes it naturally resistant to buoyancy, ensuring it stays put.
- Long-Term Reliability: A septic tank is not something you want to think about often. The 40 to 50+ year lifespan of a properly installed concrete tank means it’s a one-time investment for most homeowners. We’ve been manufacturing them since 1966, and many of our earliest tanks are still in service today.
While plastic tanks have their niche, especially for remote access sites, the evidence points to precast concrete as the most durable, reliable, and cost-effective solution for the vast majority of Ontario homes. Need help understanding your property’s soil conditions? We can connect you with trusted local installers who know the terrain, just reach out.
Installation & Longevity: What to Expect
Proper installation is just as important as the tank itself. While concrete requires a crane or boom truck for placement, this process ensures the tank is set perfectly level on a prepared bed of gravel. This stable foundation is critical for long-term performance.
Regardless of material, a professional installation is non-negotiable. It ensures your system complies with all local codes and protects your investment. Once installed, every septic tank requires regular maintenance. You should plan on having your septic tank pumped every 3 to 5 years to remove accumulated solids. An undersized or overused tank will require more frequent pumping.
A key part of long-term care is knowing the signs your septic tank needs inspection or replacement. Slow drains, foul odours, or unusually green grass over your leach field are all red flags that demand immediate attention.
Why Choose OPC Concrete Septic Tanks: A Legacy of Quality
For over 50 years, Orangeville Precast has built a reputation on quality and reliability. When you choose an OPC tank, you’re not just buying a product, you’re investing in a solution backed by decades of manufacturing excellence.
Our precast concrete septic tanks are:
- Engineered for Strength: Manufactured in a controlled environment to exceed the CAN/CSA-B66 standard, ensuring maximum durability against Ontario’s toughest conditions.
- Built for Longevity: We provide a foundational asset for your property that is designed to last a lifetime.
- Environmentally Responsible: Concrete is a stable, inert material that won’t degrade or leach chemicals, protecting your local groundwater.
Available for Any Project: We manufacture a complete range of septic and holding tanks, from 225 gallons to 5,000 gallons, along with all the necessary accessories for a complete system. Explore our full septic tank products lineup to see what fits your project.
Your Next Step: A Confident Decision
Choosing the right septic tank doesn’t have to be overwhelming. By focusing on the right size based on OBC regulations and selecting a material proven to withstand our local climate, you can make a smart, lasting investment.
Our experienced team is here to guide you. We can help you or your contractor select the perfect tank for your property and ensure you have everything you need for a successful installation.
Contact Orangeville Precast today to discuss your project. Let our legacy of quality become the foundation of your peace of mind.
Frequently Asked Questions
What size septic tank do I need for a 3-bedroom house in Ontario?
Based on the Ontario Building Code, a 3-bedroom home typically requires a minimum working capacity of 3,200 litres (approximately 700 imperial gallons). However, factors like water usage and future plans could make a larger tank a better choice.
How deep does a septic tank need to be buried?
The depth depends on your property’s grading and local code requirements. Typically, there should be at least 15 to 30 cm (6 to 12 inches) of soil cover over the tank, but no more than 90 cm (3 feet) to allow for easy access for pumping.
Is a concrete septic tank really better than a plastic one?
For most Ontario properties, yes. Concrete’s weight prevents it from shifting or floating in wet or freezing conditions. Its superior strength resists damage during installation and from soil pressure over its 40 to 50+ year lifespan, making it the most reliable long-term investment.
How often should I get my septic tank pumped?
A properly sized residential tank should be pumped every 3 to 5 years. If you find you need to pump it more frequently, it could be a sign that the tank is undersized for your household’s needs.