The Gray Water Mouse Trap

Rube Goldberg was probably the most adept illustrator in creating a genre for the design of the supposedly perfect mousetrap which in fact was typically an over-designed contraption to perform a very simple task. His comic illustrations created a following as well as a common descriptive term found in the Merriam-Webster dictionary that bears his name. The “Rube Goldberg” machine contest is now an annual competition at institutions like Purdue and UC Berkeley.

Our approach to the design that traps gray water and recycles it for use in flushing other plumbing fixtures while intricate is hardly over complicated. The design is straight forward and efficient and gets right down to the business water efficiency through the reuse of waste water. The gray water system gains the project a number of key points for achieving LEED certification as a part of the sustainable goal set by the Chickasaw Nation (the Client). While the system is supported by architectural and electrical elements, it is predominantly a mechanical engineering system and the design is showcased in the plumbing section of the construction documents. Here’s how it works.

Waste water is collected from fixtures that are suitable sources for gray water (GW). In the Visitor Center, these include; 7 lavatories (bathroom sinks), 4 drinking fountains, 1 kitchen sink, 1 janitor sink and 1 shower. The GW from these fixtures flows into a collection basin; ours is 36” in diameter by 48” tall. There are 2 pumps in the basin; one pumps water to the filter tank via a chemical injection tank and the other pumps overflow GW into the municipal sanitary sewer system.

After passing through the chemical and filter tanks, the water is now classified as non-potable water (NPW); cleaned up but not drinkable. The NPW flows into the storage tank which is 67” in diameter and 44” high. There is 2” a make-up water line that will feed water into the tank when the NPW has been used up. There are 2 pumps that work in tandem to pump the water to flush valve fixtures. These are the fixtures where gray water is acceptable for operation and in our facility which includes 2 urinals and 6 toilets. After use by these fixtures, the waste water flows into the municipal sanitary sewer system.

The Visitor Center gray water system is very discrete, unassuming, quite and hidden but performs its duty diligently throughout the day unlike the visually entertaining and noisy display of the competitive Rube Goldberg Machines.