Reclaimed Water: No Gray Area

Building codes are written for public safety. Sometimes they are quite clear and logical, sometimes they aren’t. Typically, it is disastrous situations that result in code modifications. Townhome and row house fires brought about greater fire separation between units. College dormitory fires brought about a sprinkler requirement. Occasionally, the code comes out with strong initial prohibitions to unfamiliar systems. One such situation was the use of reclaimed rainwater.

Though collected and reclaimed rainwater has been used for human water needs since the beginning of time, it was an unfamiliar commodity when introduced into the commercial building realm. So much so that collected rainwater was lumped in with all “gray” water. Gray water is water that is gathered after running through your laundry, dishwasher, down your sink or shower drain. Since the code lumped together the collected rainwater and gray water, it was all required to be chemically treated and dyed for public safety means before it was delivered to irrigate your landscape or flush your toilet. This makes sense for the soapy water out of your drain, but should it be required to chemically treat water that fell from the sky because it was gathered in a cistern before it was delivered to the earth? Some municipalities even required far-fetched labeling measures including “Non-Potable Water” signage over the toilets and urinals. (A thoughtful requirement for dogs that can read).

Fortunately, logic has set in and the latest NC Code update has separated reclaimed rainwater requirements from gray water requirements. Gray water must still be chemically treated and dyed, while rainwater requires a much simpler process. At ClearSense Properties’ 502 Rigsbee Building, we have implemented a reclaimed water system to flush toilets and provide drip irrigation to the landscaping. Less than 1” of rainwater on the roof overflows the 3000-gallon cistern. The water runs through a heavy particle filter prior to arrival in the cistern. Cistern water flows through an additional series of micron particle and UV filters before distribution through two non-potable supply lines; one to the seven toilets in the building and the other to the exterior landscaping. No chemicals or dyes endanger our pipes and fixtures from long term wear, corrosion, or staining. A solenoid valve allows for back-up use of city-supplied water in the rare event that the cistern runs dry. We are installing individual line metering to monitor the non-potable and city back up water use. Calculations based on the low flow dual flush toilets and anticipating 1” of landscape irrigation per week reveals a reduction of over 60,000 gallons per year from city water supply. (Pictured Below: Exterior cistern at 502 Rigsbee during construction.)