Water harvesting in commercial projects involves collecting rooftop rainwater, stormwater runoff, condensate from air handlers and greywater from showers, baths and lavatory sinks. This water is reused for non-potable applications such as toilet flushing, irrigation and cooling towers.

Because it offsets the use of drinking-quality water, this reuse has the potential to save millions of gallons per year for one single building.

To ensure public safety, public health agencies oversee the proper design of these systems.

To meet the demands of properly designed water harvesting systems, valves of many types are used. They control where the different types of water can and cannot go. Materials of construction vary by local code, but polyvinyl chloride (PVC), stainless steel and copper/bronze are the most common.

That having been said, there are exceptions. Projects designated to meet the “Living Building Challenge,” which requires rigorous green construction standards, preclude the use of PVC and some other materials that have been deemed harmful to the environment because of the manufacturing processes or disposal methods.

Beyond materials is design and valve type choice. The section of this article to follow looks at common rainwater and greywater harvesting system designs and how different types of valves are used within each.

In general, how harvested water will be reused and how local plumbing codes apply affect what types of valves are used. Also under consideration is the reality that, the volume of water available to be harvested may not be sufficient to meet 100% of reuse demand. In that case, domestic (potable) water may be included in the system to make up the shortfall.

The major concerns of public health and plumbing regulators are separating the domestic water source from the harvested water interconnection and potential contamination of the domestic potable water supply.