Rainwater Collection

From Island Farm & Garden

Using your resources

Don't Waste a Drop

The resourceful and sustainable living is nothing new to the Vancouver Island farmer and gardener. As environmental protection and greener living become more critical, products and systems to preserve our natural resources are improving.

Rainwater harvesting can help protect our precious Island resources and save plenty of money in the process. At its simplest rainwater harvesting consists of a roof, glitter, downspout, rain barrel, and distribution device — aka a pail, watering can, or garden hose.

Even this simple form provides much, if not all, of the water needed for outdoor watering use including irrigation of lawns and gardens, washing vehicles, decks and sidewalks, hosing off dirty critters and topping up pools, hot tubs and ponds. Add a few bells and whistles (i.e. proper treatment systems) and rainwater harvesting can also be used for all human consumption needs like washing, cooking, bathing and drinking.

The trick to a good rainwater harvesting system is getting it from the sky lathe end use wills the least amount of contamination. The end use (e.g. watering lawn vs. potable drinking water) ultimately determines the complexity of the system.

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The Roof: As Hank Aarsen of Aarsen Gutter Installation and Cleaning points out, “Slate and tile are some of the best roofing materials to use but they are very expensive. Metal is probably the most popular for rainwater collection — still very effective but considerably cheaper than slate or tile. Fiberglass is good but impractical for many applications. Asphalt shingles and wood shakes are less desirable because of their rough surfaces which can reduce flow (especially in summer) and harbour mould and mildew.” Some of the newer asphalt shingles contain chemicals to discourage growth of mould and mildew and these should be avoided if you want louse the rainwater as potable water. An optimal rainwater harvesting system considers the surface area of the roof along with local rainfall statistics in its design.

The Gutters: The average glitter installation calls for one downspout for every 40 feet of gutter. Ideally one would apply this rule in a rainwater collection system as well but because you are typically trying to move all or most of the router from a roof surface to one or two collection tanks this can often prove impractical and/or uneconomical. Aarsen points out that when you begin to exceed the 40 foot rule great care must be taken to get the pitch correct and he strongly recommends a good leaf guard system. Ihe leaf guard system is more important for the longer run because of the greater capacity to collect debris and also to reduce serious damage during snow storms (particularly if combined’with a metal roof). Finding a reputable gutter installer is always advised but in rainwater collection systems it is critical.

Debris Box and/or First Flush Diverter: Debris boxes (the more economical options) are basically filters that separate and collect the leaves and other debris from the rainwater prior toils entering the storage device, and need robe manually cleaned periodically. A first flush diverter flushes the first few gallons of water during any rain event into the overflow drainage system thereby removing a large portion of the contaminants and debris from the rainwater before it enters the storage system.

Storage Devices: These can range from a simple rain barrel to large underground concrete cisterns. As Jeff Townsend (previous owner) of ABC Water Systems in Nanaimo points out, “There is no cookie cutter answer to rainwater storage but systems can be designed to meet almost any requirements. Factors that may impact the type of storage device include the end use of the water, the quantity of stored water desired, aesthetics, terrain, and budget. For most above ground applications a plastic tank that is FDA and NSF6I compliant for drinking water is a no-brainer since these tanks are suitable for virtu-ally any application and are extremely cost effective.’ High volume storage requirements and below ground applications include a much broader range of alternatives including reinforced plastic, steel, and concrete. The size of the storage tanks required is also highly variable and careful planning and consideration is needed to build the proper system. As Torrie Jones (previous owner) of Island H20 Services explains, “While it is entirely possible to build a system that can meet virtually all of a client’s water requirements, often times these systems are not practical due to cost or space constraints and it is more economical to build smaller systems that are augment-ed by occasional/seasonal water hauling or other access to water.” Adds Jones, “Rainfall on the island can be a bit of a boom or bust proposition so having access to alternate water supply sources is recommended.”

Filtration: Like storage devices, the types of filtration avail-able for any system are highly diverse and need to be tailored to the unique needs of the project. There arc a myriad of filtration options on the market, including sediment, charcoal, reverse osmosis and ultraviolet light systems. If the end use ofthe water is simply to augment lawn and garden irrigation then little or no filtration may be necessary. If the end use is potable water for human or livestock consumption filtration will be necessary in order to meet the Canadian Guidelines for Drinking Water Quality, and regular testing is highly recommended. The type of filter(s) needed will depend on the specific conditions of the property, what the water will be used for, and many other possible considerations. Townsend recommends consulting with a water treatment specialist in order to design a safe and effective filtration system.

Rainwater harvesting can be a necessity for many home-owners as is the case when well water is either unavailable, sporadic or of very low quality. Whether or not it is necessary it is always smart — allowing a home owner to reduce the use of metered water, save money, and protect the environment by conserving water and protecting water habitats, flora and fau-na from the damaging effects caused by storm-water runoff. Rainwater harvesting, in large part or small, is a practice we should all seek to embrace.

Reference: Island Farm & Garden 

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