A: The most common cause is a flooded sewer system that is overwhelmed by rainwater, snow melt and sewage. Most homeowners in detached, semi-detached or townhomes do not realize how close they are to a sewer backup problem. The answer: 10-15 feet with no barrier to save you if you do not have a fully operational backwater valve.

In early urban development, homes were generally built near to a water source. Very often that water source (a river or a lake or the sea), became the recipient of storm water runoff and sewage runoff (after passing through a sewage treatment plant). Let’s consider these homes as being in “older” neighbourhoods. In those early days, the underground pipes were generally designed to cater to both storm water runoff as well as sewage run off, through a single pipe (this is referred to as a Combined System).

As time passed, urban planners became smarter and realized that it was better to plan homes in “newer” neighbourhoods with two external pipes, keeping storm water and sewage separate as they had different end points (storm water did not have to go through a treatment plant), and by so doing, providing greater capacity for increased flow as population grew in the area. This is referred to as a Separated System.

In theory, this was great, except for a number of factors that have surfaced over time:

1. Rapid growth of urban populations beyond what was expected by early planners
2. Climate change – leading to increased frequency and intensity of rainstorms, and
3. That the route of storm water runoff and sewage runoff still had to pass through the “older” neighbourhoods that had older infrastructure.

All of the above has the potential to create a blockage or a backup, which could ultimately lead to a sewer backup in your home if you don’t protect your home from that eventuality.