On Salt Spring Island, summers often come with droughts, while other months, especially in spring and fall, can see heavy rainfall. While we hear talk of a water “shortage” in the summer, there isn’t a shortage as much as a maldistribution. In 2021, for instance, July and August had a combined total rainfall of just 18 mm, while September and October had a combined total rainfall of 173 mm.
As I described in an earlier post, we rely on St. Mary Lake water for drinking water; this past summer, the drought led to level 4 water use restrictions. By contrast, as I write this, there is a rainfall warning and we may get more rain in a day than in June, July, and August combined!
In this kind of climate, with an abundance of rain to harvest in some months, and a need for irrigation in others, rainwater collection is both easy and important. So, last fall, and thanks to the expertise and creativity of Milo Stuart at Rainwalk Design, we had the first part of the rainwater harvesting and irrigation system set up.
Salt Spring Island is not part of a municipality, and its governance is idiosyncratic. Building codes and inspections are the purview of the Capital Regional District (CRD), while zoning and land use bylaws are the purview of the Islands Trust. After consulting with the CRD, we discovered that, if the rainwater harvesting system is intended to be used for potable water, a plumbing permit is required along with sealed design drawings from a professional engineer. If the rainwater harvesting system is simply for garden irrigation purposes, as is the case for us, then a building permit is not required. The Island Trust was able to point us to the relevant sections of the Salt Spring Island Land Use Bylaw, which stipulates the minimum set-backs from various property lines.
We chose a 4,000-gallon tank (VW 3330) from Premier Plastics, to be located away from and higher than the house. To create a stable base, layers of fill were added to the site, and tamped down after each layer. The top layer is pea gravel, so that no sharp rock edges damage the tank.
A smaller transfer tank (RWF BX50) next to the carport collects the water off the roof, and a pump moves the water to the large tank every time the floater hits a certain level. Because the large tank sits higher than the house and garden, drip irrigation can be gravity fed. When the large tank is full, the transfer tank can be disconnected to stop collecting, and the pump can be removed to protect it from any heavy frost.
This fall, we had a second, 1,500-gallon tank (VW 1280) installed to collect rainwater off the other side of the roof. The tank is fed directly by the roof, so without transfer tank or pump. It will be used to drip-irrigate parts of the garden behind the house. We plan to paint the white pipe across the chimney this coming spring!