Starting July 1, 2025, the City of Vancouver is introducing new rainwater management requirements for most new home construction projects. These changes are meant to help reduce the risk of sewer overflows and flooding by slowing down how fast rainwater flows from private properties into the city's storm sewer system.
In this article, we’ll break down:
- Who the new rules apply to
- What’s actually required
- What a detention tank is and why it matters
- What you’ll need to do during your building or renovation project
- What products can help you comply—without added stress
Why Is Vancouver Changing the Rules?
Vancouver’s current sewer system struggles to keep up during heavy rainstorms. When rainwater flows too quickly from rooftops, driveways, and other hard surfaces, it can overwhelm the system and cause combined sewer overflows (CSOs)—where untreated water ends up in natural waterways like Burrard Inlet or English Bay.
The city wants to reduce this risk by making new buildings manage their own runoff more effectively. This means storing and slowly releasing rainwater, rather than sending it straight into the storm sewer all at once.
Who Do These New Rules Affect?
The new requirements apply to most new houses and some renovations that qualify as “new builds.” Specifically:
✔ You’re affected if:
-
You’re building a brand new home in Vancouver
-
Requirements apply to new construction.
❌ You’re not affected if:
-
You’re doing a small renovation or alteration that doesn’t change the structure or foundation
-
You’re working on float homes, marinas, or accessory buildings (e.g., sheds, detached garages)
It’s always best to double-check with your builder or contact the City if you're not sure.
What Exactly Is Required?
If your project falls under the new rules, you’ll need to include a detention tank in your plumbing system. The size of the tank depends on your lot size and the floor space ratio (FSR).
There are two compliance pathways:
1. Engineered Pathway (Existing)
Required for larger or denser developments (FSR over 1.0 or site size over 1,000 m²)
- Must be designed by an engineer
- Requires specific flow control calculations, drawings, and inspections
2. Small Site Pathway (New)
- For typical single-family lots under 1,000 m² and FSR of 1.0 or less
- No engineer required
- Use a pre-approved detention tank sized by your lot area
- Plumbing specs verified during the plumbing permit stage
If your project qualifies for the small site pathway, the process is much simpler—just install the right tank, and you’re good to go.
What Is a Detention Tank?
A detention tank is a specially designed water tank that temporarily holds rainwater and releases it slowly into the storm sewer. It helps reduce pressure on the city's drainage system during heavy storms.
Key components of a detention tank system:
- Orifice plate: Controls the release rate of water
- Overflow outlet: In case the tank fills beyond capacity
- Trap: Prevents sewer gases from coming back into the home
- Backwater valve: Protects against sewer backups
- Cleanouts: Allow maintenance access to overflow and outlet lines
Unlike rain barrels or cisterns for reuse, detention tanks are designed strictly to manage flow—not store water long-term.
How Big Does the Tank Need to Be?
Tank size is based on the lot area. The City of Vancouver has set the following requirements:
|
Lot Size (m²) |
Active Storage (Liters) |
Orifice Diameter (mm) |
|
≤ 400 |
3,400 |
30 |
|
401–500 |
3,900 |
35 |
|
501–750 |
4,600 |
45 |
|
751–1,000 |
7,200 |
50 |
Note: “Active storage” means the volume of water the tank holds before it overflows—this doesn’t include extra volume below or above the outlet. The orifice ensures the water drains at a controlled rate.
What If There’s a Problem with Installation?
Sometimes it’s not possible to install a standard tank—for example:
- High groundwater levels
- Contaminated soil
- Protected trees or roots in the way
- Archaeological sensitivity
- Structural limitations
In those cases, the City may allow above-ground tanks or alternative solutions, but you’ll need supporting documentation and approval from the Chief Building Official.
What’s the Timeline?
Here’s how the rollout works:
📅 September 26, 2024: Public comment period closes
🏛️ November 2024: Final report to City Council
🧑💻 Early 2025: Open Q&A sessions begin
🚨 July 1, 2025: Regulation goes into effect
Transition rule:
If you submit a Development Permit (DP) before January 1, 2025 AND submit your Building Permit (BP) before January 1, 2026, your project is exempt from the new requirement.
Choosing the Right Tank: Why Quality Matters
It’s tempting to go with the cheapest option—but not all detention tanks are equal. In fact, some cheaper models may not meet the City's structural or performance standards.
One proven option is the GRAF Platin series, supplied locally by BARR Plastics. These tanks are:
✅ Pre-sized to meet the City's required capacities
✅ Made from recycled materials
✅ Structurally rated for underground installation—even under driveways
✅ Equipped for overflow, traps, and backwater protection
✅ Shallow in depth, reducing excavation and install costs
Cheaper tanks may require extra framing, take longer to install, or not include all necessary fittings—leading to inspection delays or costly corrections.
Can I Reuse Rainwater from the Tank?
While the detention tank itself is only for flow control, you can add a rainwater reuse system to collect and store rainwater for:
- Toilet flushing
- Garden irrigation
- Laundry use
- Car washing
The reuse system would be separate and must meet the requirements of Vancouver Building By-law Section 2.7. Rainwater reuse does not reduce the required detention tank size.
What Happens During Permit Review?
If you're using the small site pathway, the City will check your detention tank plan during the plumbing permit review stage. You don’t need:
- Engineered drawings
- Schedule B letters
- A separate permit for the tank
Just install the correct tank with proper fittings, and you’re good to go.
What If I Have Questions?
Here are some common questions and answers:
Q: Does this apply to my detached garage or shed?
A: No. Accessory buildings are exempt.
Q: Is a sump required after the tank?
A: No, but you must include a trap to block sewer gases.
Q: Can I place the tank in my backyard?
A: Yes. There's no required location, though the front yard is often more practical due to sewer access.
Q: Will the City publish an approved products list?
A: Not officially—but BARR and others may be listed as suppliers with compliant products.
Q: Can I use a blue roof or green roof instead?
A: Only under the engineered pathway, not the small site option.
Final Thoughts: Stay Ahead of the Change
Vancouver’s new stormwater management regulations are a smart step toward a more flood-resilient city—but they do add a new layer to building or renovating a home.
If you’re starting a project in 2025 or beyond, don’t wait until the last minute. Make sure your team is aware of the requirements and chooses a solution that meets code and simplifies the process.
Working with experienced suppliers like BARR Plastics ensures you get the right tank, the right fittings, and the right advice.
Need Help?
BARR Plastics can help you:
- Choose the right tank based on your lot
- Supply code-compliant solutions locally
- Provide product specs for your permit package
- Support your contractor during installation
👉 Reach out today to get a quote or expert guidance:
📞 1-866-790-6753
🌐 www.barrplastics.com
Useful links: Rainwater management on private property | City of Vancouver
Need a Simple Way to Meet Vancouver’s New Rules?
BARR Plastics has you covered with ready-to-go detention tank solutions that meet the City of Vancouver’s 2025 stormwater requirements—no engineering needed.
Want to see what works for your lot?
Get info about BARR’s stormwater detention tank solutions- Tank options sized to match your lot area
- Systems built for quick, stress-free installation
- Local support and product specs for your permit
