Rainwater harvesting saves money

Paula Gasparro, Manager, Business Development, Multi-Unit Mortgage Insurance, CMHC
Friday, June 14, 2013

Is rainwater harvesting an effective way to reduce water bills and demands on local infrastructure?

In short, the answer is yes.

For centuries, people have collected rainwater for drinking, washing and irrigation purposes. With the advent of municipal water treatment, rainwater collection became less popular in urbanized centres, though water storage cisterns can still be found in old farmhouses across Canada. But recently, rainwater harvesting has experienced an increase in popularity in countries around the globe as a result of droughts, water shortages, and the rising costs of drinking water and stormwater infrastructure. Canada, too, is experiencing an increase in rainwater harvesting for lawn and garden irrigation, and many municipalities have begun to offer rebates for rain barrels. But larger, more sophisticated systems that capture, store, treat and redirect greater quantities of rainwater for other uses are still relatively new.

Some municipal planning codes now permit the use of non-potable (not safe to drink) water for toilet flushing and subsurface irrigation, while others permit the use of rainwater for laundry washing. Codes and bylaws set out requirements for the appropriate materials to be used, sizing, supports, protection and marking, as well as the steps needed to ensure non-potable water does not mix with potable (drinkable) water from the municipality or a well. Before installing a rainwater harvesting system, it is important to check to ensure the design and installation of the system will be in compliance with local regulations.

Depending on what the rainwater will be used for, a system can range from very small and simple to large and complex, with the cost varying accordingly. A general rule of thumb is a system will cost $1 per litre. So, a smaller 2,000 litre system will cost approximately $2,000.

The first step is to determine the quantity of water required (for the intended purposes), the size of the roof catchment area and the amount of rainfall the area typically receives in a year. Based on this information, a rainwater harvesting system designer can help determine how much rain will be realistically collected, how big of a cistern will be required and what the water can be used for. Cisterns have come a long way from the simple rain barrel. They come in different sizes and materials, and can be installed above or below ground.

Paula Gasparro is manager, business development, multi-unit mortgage insurance for Canada Mortgage & Housing Corp. (CMHC).

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