What is the definition of water backflow?

” Water Backflow ” essentially means the flowing back of water or reversal of the normal direction of water flow in either the Water System or a Customer’s Plumbing system into the public domain or water source

How does water actually backflow?

Water flows from the public line into your home everyday.  The average person in Calgary consumes 7,000 litres of water per day. Depending on the devices and water needs your home might need contaminated water may find itself back into the water supply without you even noticing it!


Clean water flows in the
home or business

Regular water flow

Water is then used and
is contaminated

Water is used at home

Sudden changes in pressure
can reverse the flow

Sudden changes in pressure

Polluted water backflows
into water supply.

Contaminated water backflow

Normal water use should go only one way. From the public supply line to the home or business and then to waste.

Water Backflow devices are there to prevent that any sudden changes in pressure or water use alter the flow of the water in the opposite direction. This so-called ‘backflow’ can be triggered with a simple break in the main water line. When pressure is lost during these events, water is no longer being pushed forward into your home and will flow backward into the city of Calgary water supply.

Backflow can pollute the public drinking supply with a variety of different contaminants used in the average house or business.

Common water contaminants can be:

  • Gardening additives and fertilizers
  • Human and pet waste
  • Chlorine and other sanitizers
  • Soap residues from dishwshers
  • Food grease
  • solid waste such as personal higiene supplies

The list of all the different types of contaminants that can flow back to the public water supply is big. Image just a single cigarrette butt can actually contaminate 20 litres of water!

This is why testing water backflow prevention devices is so important. these devices will trigger a stop to the backflow in case of the event of water backflow. Once the stop is triggered no water can flow back into the public water supply.

Here are some examples of water flows and reservoirs where contaminated water backflow can end up in Calgary

Glenmore Reservoir

Glenmore Reservoir

Bow River

Bow River

Elbow River

Elbow River

The Glenmore reservoir is Calgary’s most critical potable water body. This reservoir is closely monitored by the City of Calgary. Because of its importance water recreationa activities are restricted ( such as swimming in the water ) to avoid contamination.

Thank you for keeping our water clean

Prisitine water