4.9.4 Infeasibility Criteria

Assessing the feasibility of using a rain water harvest system should include both technical and economic considerations. Rain water harvest systems are technically feasible for most sites where applicable local setback requirements for structures can be met. In areas with little rainfall, the systems will supplement, rather than replace, other domestic sources of water. Rain water collection systems may make a project situated in a challenging drainage basin more easily developable because stormwater from roof surfaces can be collected and used for a variety of non-potable uses.

From a technical design perspective, rain water harvesting systems should not be used to collect stormwater from roof materials containing contaminants such as zinc, copper, or lead. Depending on the facilities connected, a rain water harvest system could spread these contaminants throughout a site through the irrigation system or bring the contaminants into contact with humans through non-potable water re-use.

In very rare instances, there may be entitlement challenges associated with constructing a rain water harvest system. A rain water harvest system would require a water-right only if more than 5,000 gallons were to be collected daily.