Before we can recycle greywater, it has to be kept separate from its foul-smelling sibling, blackwater—the highly contaminated and more difficult-to-treat wastewater that issues from toilets and kitchen sinks. “The concept of separation sounds simple, and it is,” says Ron Flax of Rodwin Architecture in Boulder, Colo., “but it requires planning.” Flax knows, because he was project manager on the hyper-ecological Edge House, which featured Boulder’s first permitted greywater-recycling system.
Just like all sewage disposal, greywater piping is gravity fed and requires a downhill route to the point of treatment or stub-out. “This can mean having to build extra-wide plumbing walls to accommodate a double sewage line,” explains Flax, especially when multiple greywater sources have to be combined. Greywater sewer lines require their own venting as well.
The sewer side of the equation requires no special type of pipe. But reclaimed greywater headed for reuse—especially when in the home—must flow through clearly marked purple pipe, as specified by both the Uniform and International Plumbing Codes (UPC and IPC). Many PEX manufacturers nowadays offer a purple pipe labeled “non-potable.” But when Flax installed the first greywater system in Boulder, “We couldn’t find purple pipe, we had to paint it by hand, and affix ‘non-potable water’ labels to the full length of every pipe.”
On the treatment end, you will find many engineered greywater systems for sale, but the features of an individual system may not comply with the specific requirements of your area. Generally the requirements include a sealed, gas-tight reservoir of 50 gallons or more. The reservoir will have to have a valve that clears the greywater into the sewer system automatically if left standing for 72 hours, and the reservoir will require its own vent. You will have to provide makeup potable water to keep the system functioning even when there’s no greywater available. The makeup water will require its own backflow preventer to keep greywater from being drawn back into the freshwater supply.
Mike Vale, who designed and built the Water Legacy greywater treatment system installed at the Edge House in Boulder, says one of the recurring errors in greywater installation is not providing space for the water heater–size treatment appliance. “Allow plenty of room around the treatment tank, so you can easily get to it for servicing,” says Vale, who now manufactures and sells the Water Legacy system nationwide. Recycling tanks are located in the same utility closets where water heaters may go, in basements, laundry rooms, or even garages or outdoors in warm climates.
When specifying a greywater recycling system, it pays to check with the building department first to make sure the system you intend to use meets local requirements. Then carefully blueprint the plumbing tree, forestalling hours of skull-peeling, head-scratching problems at the jobsite.
The greywater sources you can legally recycle vary by jurisdiction, but Florida’s regulations typify the usual assortment: bathtubs, showers, lavatories, clothes washers, and laundry sinks. Together, these represent about 40% of the water waste discharged in the average home, according to EPA estimates.
Drought-stricken areas, such as California and Arizona, have recently jumped head-first into greywater permitting, and, in some cases, even provide tax credit incentives for homeowners to install the systems. Since June 2010, Tucson has required builders to plan for and stub-out greywater plumbing for future hookup.
The most aggressive states encouraging greywater recycling include Arizona, California, New Mexico, and Texas. But even traditionally conservative areas, such as Nebraska, have rolled out the grey carpet. Georgia’s statewide plumbing code adopted in 2009 permits the use of filtered and disinfected greywater for toilet and urinal purposes and for subsurface irrigation.
Unlike many high-end energy-saving measures, which can provide handsome dividends, the payback for indoor-quality greywater treatment discourages many from making the investment. Even the least expensive systems may require a five- to 10-year payback at a water-savings rate of $20 to $30 per year.
In the U.S., combined water and sewer bills average about 2 cents a gallon, or less than 0.5% of household income, according to the EPA. Because of the protracted payback, sometimes beyond the lifespan of the greywater system itself, many people installing water recycling measures do it for purely environmental reasons. But for those with large irrigation needs, or with private sewage disposal systems, it can make financial sense.
In drought-prone areas such as California and Arizona, where landscape watering can represent nearly 70% of a household’s consumption, according to a 2010 study commissioned by the California Homebuilding Foundation, low-tech, outdoor-only greywater recycling systems make good economic sense, especially when punitive over-consumption fees go into effect. Payback varies by usage, with high-consumption homes such as those with orchards or large yards obtaining ROI in as short as three to five years.
For those on private disposal systems, the reduction in effluent from diverting greywater from leach lines also can make it possible to build on a lot otherwise too small for a standard septic system. In fact, some systems exist that treat combined black and greywater for subsurface irrigation, such as the Puraflo wastewater treatment system.
For now, greywater in the U.S. is still in its beta-test phase. Like early solar panels, greywater recycling systems have to prove themselves before they become a standard branch in the garden-variety plumbing tree.
But costs are slowly coming down, and just like alternative energy, municipal subsidies are helping the industry inch forward. In some areas, such as San Francisco, permissive regulations allow homeowners to install the smallest, simplest, and least costly systems without a permit. In most cases, these systems are also the ones that make the most economic sense.
Fernando Pages Ruiz is a green builder and author based in Boulder, Colo.
To see images of the Edge House, click here.
To view an additional case study, from Chapman Cos. in Santa Fe, including a greywater diagram, click here.