Ministry drafts guidelines for harvesting rainwater for potable use

Derek Kilbourn

Sounder News

Wednesday, September 4 2019

The Ministry of Health has release draft guidelines which, if approved, will mean rainwater harvesting would be approved as a source for potable water in the Province of BC.

Under current regulations, property owners of a single-family home can use rainwater as a potable water source, but any commercial use (including for B&Bs or if renting out a single-family home), is not permitted.

Ministry officials provided a copy of the guidelines to the Sounder this past week - saying the guidelines have gone out to various stakeholders for comment. This will include the Regional District of Nanaimo (RDN), in particular steering committee for the RDN’s Drinking Water and Watershed Protection Program.

Feedback on the guidelines is due by October 31, 2019.

The guidelines are, as the Ministry explains in the document, conservative, but most of the guidelines and recommendations point to the existing guidelines detailed in the Guidelines for Canadian Drinking Water Quality (GCDWQ), as developed and updated regularly by Health Canada.

The intent of the guidelines is to assist in ensuring harvested rainwater is made potable.

It includes a list of potential risks involved with harvesting rainwater, such as airborne contaminants; contaminants likely found on a roof; how different roof materials may impact the quality of water; the siting and design of cisterns/storage units; and other best practices.

The draft document does not address:

• Non-potable uses of rainwater. 

• Stormwater runoff as harvested rainwater;

• Assessing collection capacity, storage volumes, reliability nor sustainability of rainwater as a source of domestic water;

• The appropriateness of rainwater sources as basis for subdivision approval; or

• Standards for chemical contaminants. It recommends that as with other sources, rainwater chemical parameters should be reviewed against the GCDWQ.

The guidelines do address assessing microbiological, chemical and physical risks to collected rainwater, and applying appropriate treatment to mitigate those risks. 

Ministry staff say whether rainwater collection is a suitable as a source for water for subdivision approval (i.e. in terms of whether rainwater collection and storage can be relied on to provide for all year-round water needs without a back-up source) is outside the scope of the Drinking Water Protection Act and this document.

That decision, if the guidelines are approved, will fall to the local subdivision approving authorities - which on Gabriola would be the Islands Trust and Ministry of Transportation And Highways.

Staff add that rainwater, if treated appropriately for risks inherent to it’s collection, storage and distribution may be used as a source of potable water for drinking water supply system regulated under the Drinking Water Protection Act. 

Should this guideline be finalized, it will set expectations for assessing these risks and applying appropriate treatment.

According to Ministry staff, the guidelines have been written with involvement from health authorities and ministry experts - as well as members of the gulf island communities where the demand for this kind of document has been growing in recent years.

Staff said, “many communities have expressed interest in developing rainwater collection systems capable of providing potable water to users.

“The Ministry is inviting feedback on this proposed guidance from interested stakeholders and is distributing this to parties that have expressed interest in the subject.   A copy of the proposed guidance document is attached to this e-mail.  Please send any feedback or questions to by October 31 2019. 

A PDF of the guidelines can be accessed by clicking here.