Managing water around a home is critical—especially during wet Lower Mainland winters.
On a recent project in Burnaby, we faced a common drainage challenge: the home’s perimeter drains sit lower than the available city storm connection. Without the right system in place, groundwater could not flow naturally away from the foundation.
Here’s how we designed the drainage system to manage water efficiently and protect the home.
Understanding the Elevation Challenge
The city storm inspection chamber on this site is approximately 6½ feet below grade.
However, the home’s perimeter drain tile, installed around the footings, sits approximately 10 feet below grade.
Because the drain tile is lower than the city connection, water cannot simply flow downhill by gravity into the city storm system.
To solve this, the home needs a system that collects groundwater and pumps it to a higher elevation before it can drain away.
The Storm Sump System
At this project, we installed a five-foot storm sump that extends approximately 13 feet below grade.
The sump collects groundwater from the perimeter drain tile system. Since the drain tile is installed at the footing level, it directs water into the sump instead of allowing it to build up around the foundation.
From there, the water is pumped upward.
Why We Use Duplex Pumps
Inside the storm sump, we use duplex pumps.
Duplex pumps are two pumps working together to provide dependable water management. They help ensure the system can continue operating if one pump requires maintenance or if there is a higher volume of water during heavy rainfall.
The pumps lift groundwater from the deep storm sump to a smaller gravity sump located at a higher elevation.
Once the water reaches the gravity sump, it can flow naturally to the city storm connection.
Gravity Drainage Whenever Possible
At Clay Construction, our goal is to use gravity drainage wherever possible and only pump water when necessary.
Pumping requires mechanical equipment and electricity, while gravity systems allow water to move naturally through the drainage system.
On this project:
- Groundwater from the perimeter drain tile flows into the deeper storm sump.
- Duplex pumps lift the groundwater to the higher gravity sump.
- Water then flows by gravity from the gravity sump to the city storm system.
This approach provides reliable drainage while minimizing the amount of water that needs to be mechanically pumped.
Managing Roof Water Separately
Roof water is managed through a separate system installed above the draintile system.
Rainwater from the gutters flows into dedicated rainwater leaders. Because this water begins at a higher elevation, it bypasses the deep storm sump and flows directly into the gravity sump.
From there, it drains by gravity to the city.
Separating roof water from groundwater helps create a more efficient and organized drainage system.
A Complete Water Management Strategy
This Burnaby home uses a layered approach to water management:
- Perimeter drain tile at the footing level
- Deep storm sump for groundwater collection
- Duplex pumps to lift groundwater
- Gravity sump connected to the city storm system
- Separate rainwater leader system for roof runoff
Together, these components help protect the foundation and ensure water is safely directed away from the home.
Building for the Lower Mainland Climate
Water management is not an afterthought. It is a critical part of foundation design, especially in areas with heavy rainfall and challenging site elevations.
By understanding the site conditions and designing the drainage system accordingly, we can protect homes from water buildup, moisture issues, and long-term foundation concerns.
At Clay Construction, we build drainage systems with one simple principle in mind: gravity what can be drained with gravity and pump only the water that can’t be drained via gravity.
— Larry Clay
The Clay Way
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