What is a two pipe drainage system?

A two pipe drainage system is setup to separate the collection of Ground Water from Rainwater. The Groundwater is collected by perimeter drains and flows away from the foundation. The Rainwater is collected from the Rain Water Leaders/Downspouts in a separate pipe usually above the perimeter drains but in the same trench.  Two pipe drainage systems are required in BC building code. Check the code in your area to see if a two pipe system is required.