Gray Water Gardens

The possibilities and pitfalls of guerrilla plumbing


Boise residents consume more than four times as much water in summer months than in the winter, with most of that water either pumped out of sprinklers or poured from watering cans. Keeping Boise's abundant lawns and landscapes green not only costs a lot of green, it's one of the least "green" things you can do. That's why, in lieu of paving their front yards or installing synthetic grass, a handful of locals are deciding to go gray.

Gray water is untreated household wastewater that has not come into contact with toilet waste, or black water. It includes water used in showers, dishwashers, washing machines and sinks. Gray water isn't potable, but it is currently being used by cunning DIY plumbers around the country to water trees, lawns, flower gardens and even to flush toilets. California is leading the pack with informative gray water Web sites like Santa Barbara's and Oakland's Though it might seem like a no-brainer to collect and reuse this water—which can account for 50 to 80 percent of residential wastewater—there are a number of contentious issues surrounding the practice.

To start, most simple residential gray water systems are illegal. The Uniform Plumbing Code, as adopted by the state of Idaho, permits gray water systems but includes an exhaustive list of specifications for how they must be installed.

"The way that our codes have been adopted by the state, we actually don't allow reclaimed water systems in houses, but we do allow gray water systems," explained Jenifer Gilliland, building division manager for Boise Planning and Development Services.

Because gray water can contain a variety of solids, soaps and potentially harmful types of bacteria, many homemade gray water systems "reclaim" the water by running it through a sand or vegetative filtration process before it's used. But this practice isn't permitted under the UPC's guidelines. A legal gray water system should keep wastewater from ever coming into contact with the air. It also cannot reuse water from kitchen sinks or dishwashers due to high bacteria content and is required to flow into an approved watertight tank before being pumped six inches underground through a perforated drip irrigation system into the soil.

"A lot of times, people think that 'all I need to do is put a hole in the side of my house and divert a pipe out there,'" said Gilliland. "But it's a little bit more involved than that, just because with gray water, you do have the potential for bacteria to spread, especially if the water pools up."

But there are a number of people who have created simple, hole-in-the-side-of-the-house systems anyway. Nurse practitioner Babette Munting disconnected the hose from her washing machine and runs it out her window into her backyard flower bed. Munting used to live in Troy, Idaho, with a shallow well, so she's used to being resourceful with her water supply. Sustainable architects Doug Cooper and his wife Sherry McKibben, also have a similar system that bypasses their laundry drain and collects the gray water in outside rain barrels with hoses attached to water their lawn.

"We had a learning curve; we used a borax-based detergent which is good for the sewer system, but it turns out to be very bad for plants," explained Cooper.

At this point, most Boiseans haven't moved past the disconnected-washing-machine-hose model. Installing a more elaborate gray water system often involves cutting through walls, running extensive amounts of piping, inside and out, and hooking up pumps to move the water when gravity won't do the trick. A tricked-out system can quickly cost more than you might end up saving—on water bills or the environment.

"The question is, if it costs you less to conserve versus if it costs more to conserve. There's a difference between first costs and life-cycle costs," explained Johanna Bell, stormwater program coordinator for the Boise Public Works Department.

Though residential gray water systems reduce water consumption at the micro level, industrial-sized systems tend to yield higher economic and environmental returns. The LEED Platinum-certified Banner Bank building downtown is an example of a large-scale gray water operation that is already paying for itself. The building consumes 60 to 80 percent less water than other buildings its size due to a system that recycles water used in the building's 48 sinks. Developer Gary Christensen worked with Musgrove Engineering to design a system that collects stormwater from the rooftop and the 7.3 acres surrounding the site. Though they no longer collect off-site water due to the high amounts of debris, the building's gray water and treated rooftop stormwater are collected in a 20,000 gallon tank and used to flush all of the building's toilets.

"Usually what happens on large commercial buildings is that it's the payback period of, they might put in this expensive system, but on their water bill and their energy bill, within a couple of years, they've made up the cost of the system," noted Gilliland.

Dave Krick, local foods advocate and owner of Red Feather Lounge and Bittercreek Alehouse, is not only looking at installing a gray water system that could provide water for a rooftop garden, but he's also considering the heat recovery possibilities inherent in a kitchen gray water system. When incoming cold water used for dish washing or hand washing is pre-warmed by gray water, it can reduce heat energy consumption by up to 60 percent.

"We spend a lot of water just rinsing things off, and it's water that can definitely be reused," said Krick. "I'm totally interested in the [gray water] idea. I'm hoping that by the time we get to that point that enough other people will have done it."

Though many people in town are interested in gray water's potential, they seem to be waiting for someone else to develop a viable pilot that is both inexpensive and sustainable.

"There are a lot of people who are interested, but not a lot of people who have gone much beyond that," said Annie Moore, who's considering a gray water system. "I think by making [legal systems] so prohibitive, they encourage people to bootleg it."

That's not to say the city doesn't support water conservation. In 2006, Mayor David Bieter signed the U.S. Mayors Climate Protection Agreement, which aims to reduce greenhouse gas emissions 7 percent by 2012. Though the city has plans to improve water efficiency, gray water use is still mired in controversy. Many home owners would like to see updated, more lenient, gray water regulations, but it will probably take the city a while to change the code. In the meantime, people interested in installing more elaborate residential gray water systems, like Boise Sustainable Living Community member Jay Blackhurst, will have to concoct their own conservation plans and wait for the city to catch up.

"You can't wait for the establishment or the institutions to tell us when to do it, we just have to do it because it feels right," said Blackhurst. "We have to break through those barriers. It's easier to ask for forgiveness than it is to ask for permission."