Rainwater Harvesting

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.

Rainwater harvesting systems use rainwater collected from the roof and should not be confused with systems that recycle treated wastewater or greywater (water from baths, showers and laundry). Rainwater that has touched the ground is generally not collected, as it can be contaminated with leaked automobile fluids, road salt, pet droppings, pesticides, fertilizers and dirt.

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 will set out requirements for the appropriate materials to be used, sizing, supports, protection and marking, as well as the steps needed to ensure that non-potable water does not mix with potable (drinkable) water from the municipality or your well. Before installing a rainwater harvesting system, it is important to check with your municipality first to ensure the design and installation of your system will be in compliance with local regulations.

Depending on what you wish to use your rainwater for, your system can range from very small and simple to large and complex, with the cost varying accordingly. A general rule of thumb is that your system will cost $1/litre so that smaller 2000 litre systems will cost around $2,000. The first step will be to determine the quantity of water you will need for your intended purposes, the size of your roof catchment area and the amount of rainfall your area typically receives in a year. Based on this information, a rainwater harvesting system designer can work with you to determine how much rain you can realistically collect, how big of a cistern you will need and what you can use this water for.  Cisterns have come a long way from the simple rain barrel. They come in different sizes (50 – 200,000 L), shapes (rectangular, square, cylindrical, bag) and materials (concrete, fibreglass, plastic, steel, wood) and can be installed above or below ground. Cisterns and related components should be insulated or emptied to avoid freezing in the winter months.

While there are currently very few regulations for rainwater quality, a rainwater harvesting system can include some level of treatment to stop the system from clogging up and to help ensure good water quality. Gutter filters, screens and systems that divert the “first flush” of rainwater are used to reduce the amount of leaf litter, insects, pollens, dust and other pollutants that can collect on roofs and get into the rainwater system. Screens are also used on access openings on the cistern to keep out insects, rodents, etc. Stored rainwater can also be treated with cartridge or membrane filters and then disinfected with chlorine or ultraviolet light prior to use. Check with your local health agency to determine what treatment (if any) is required in your jurisdiction. Once installed, it will be necessary to maintain your system as per the manufacturer’s instructions to ensure optimal performance. It is important to inspect and clean out gutters, check filters and check for leaks at least once a year.

In most cases, you will need a pump to deliver the treated rainwater from the cistern to the garden or your house. It is important to ensure that all plumbing and piping for the distribution system are adequately sized and installed for optimal flow. Consideration must be given to redirecting excess rain to a soakaway pit or infiltration trench to prevent the cistern from overflowing during heavy storm periods. Consider having your system designed, installed and commissioned by a professional.

Rainwater harvesting systems offer an effective way to reduce your water bills, use plant-friendly water in your garden and reduce your demands on local water infrastructure. To learn more about rainwater harvesting systems, visit CMHC’s website (www.cmhc.ca) to view the consumer guide to rainwater harvesting, or call 1-800-668-2642 to request a copy of the publication.

For over 65 years, Canada Mortgage and Housing Corporation (CMHC) has been Canada’s national housing agency, and a source of objective, reliable housing information.

Published: June 6, 2013

Auxiliary Water Sources

How to Supplement the Water Supply in Your Home

Canadians enjoy some of the highest-quality water in the world. But despite our abundant supply of fresh water, it remains, by its very nature, a valuable resource that should be conserved and protected — particularly in those areas of Canada facing water shortages. As a result, more and more Canadians are paying attention to the amount of water they use and are cutting back by using water wisely and purchasing water-efficient fixtures and appliances.

Another way to conserve water is by using auxiliary water sources — if permitted — to supplement and conserve the local public water supply. Auxiliary water includes everything from rainwater collected from your downspouts, to “greywater” that’s collected from the laundry or shower, treated and reused for non-drinking purposes around your house.

If you’re thinking about using auxiliary water sources in your home, Canada Mortgage and Housing Corporation (CMHC) offers the following tips on how to supplement your water supply while keeping your family safe and healthy and not running afoul of local building regulations:

• If you’re building or renovating a house, find out from your local building department what’s allowed, what is not and what may be required to get municipal approvals. 
• Auxiliary water sources must use a separate plumbing system so it is not mixed with your potable water. Talk to your builder, architect, renovator or plumber as early in the process as possible about including auxiliary water-ready components in your home. This may include dedicated piping for auxiliary water as well as any related storage and treatment systems. Planning for those components now could save you a great deal of time and money in renovations later whether or not you include the auxiliary supply today or at some point in the future.
• Work with your contractor to determine how much water and what level of water quality is needed for different uses in your home. This will help ensure the system is designed properly and will be able to supply all the water your family needs, at whatever level of quality you require.
• Make sure you know where the water you’re collecting comes from, and what you will be using it for. Not all of the water you collect from different fixtures can be used for the same purposes. For example, water that’s collected from your shower might be safely treated and reused to flush your toilet. But only fully potable (or “drinkable”) water should ever be used in the shower itself. Again, make sure you check with your municipality.
• Depending on what you are using the auxiliary water for you may also need to think about storing the water before it is used. For instance, rainwater collected from your downspouts to water your lawn is often used immediately, without any further treatment. But if you’re collecting greywater for use in toilet flushing you may need to treat and store that water so it is available when you need it.
• Lastly, find out what programs or regulations are in effect in your area when it comes to auxiliary water. Some communities, like the City of Guelph, offer rebates for homeowners who use auxiliary water. Other cities may have rules in place that limit which kind of water you can reuse. Always check with your local municipality or water authority before you install an auxiliary water system in your home.

To find out more about auxiliary water sources, or for information on any other aspect of owning, maintaining or buying a home, visit our website at www.cmhc.ca or call CMHC at 1-800-668-2642. For over 65 years, Canada Mortgage and Housing Corporation (CMHC) has been Canada’s national housing agency, and a source of objective, reliable housing information.

Published: October 17, 2013