#14 – Drainage

Continuing the same thread on drainage from our last column on gutter systems, once the roof drains and gutters are cleaned and downspouts properly connected, we can be reasonably sure that rain water won’t present a problem…..Or will it..??

Many folks from the Prairies will remember that their downspouts often ended at the ground and the water was left to drain into the surrounding soil. On the West Coast, the volume of rain water is substantially higher and the BC Building Code includes specific requirements for the downspouts’ connection to the underground drain system that must be installed around every building’s perimeter.

Traditionally, a 4 inch, perforated pipe located at the foundation footings was considered adequate for the dual purpose of accepting water from the roof drains and from the underground water table when it rises against the footings and foundations.

The last revision to the Building Code made changes to the requirements and now two separate systems of piping – one for the roof drains and other for the ground water drainage – must be installed. This is intended to eliminate the potential for debris from the roof drains to plug up the piping system necessary to keep water from seeping through the foundation walls from the surrounding water table.

Other Code changes require the use of heavy grade PVC piping which replaced a much more fragile type called “Big O”, which was easily damaged. Owners of older structures should be aware of the difference and be prepared for the potential replacement of damaged or deteriorated piping.

Aside from those already noted, other conditions such as overgrown trees and landscaping can clog up the pipes with roots and dirt, thus restricting their ability to drain water away from the building.

The question, “How do we tell if there’s a problem?” leads to the recommendation that a scheduled high pressure flushing of these drainage systems be included as part of any planned maintenance program.

If it’s more than 5 years since they were cleaned, we recommend a competent drainage contractor be engaged to do so. From that time on, we suggest a scheduled flushing every 3 to 5 years. Although many contractors can provide a video camera inspection of the piping, we won’t recommend this unless problems are encountered while cleaning out the lines.

John Grubb is a Property Maintenance Consultant serving Strata Corporations and building owners on Vancouver Island.

To Next Article: Strata Strategies #15 – Landscape Planning