Greywater Irrigation and Rainwater Harvesting Systems
A ReWater® system creates numerous environmental benefits including:
Water conservation comes from reusing half the water from inside a residence, and also by using that water at least 30% and up to 60% more efficiently than sprinklers in our underground drip network.
According to numerous studies on greywater usage including the renown American Water Works Association's 1999 National Residential End Uses of Water report, a typical person produces 39.1 gallons of greywater per day. An average home has 3.2 people in it, which results in the production of 125 gallons of greywater per day. This equals 45,668 gallons of greywater per year per home with the average of 3.2 people living there.
This water is then used in our underground drip irrigation network. According to a 1998 USDA, C.R. Camp, analysis of all available studies on underground drip irrigation, underground drip irrigation is at least 30% more efficient than spray irrigation, which the vast majority of residences would otherwise use for irrigation. This 1.3 efficiency multiplier means the 46,000 gallons is equivalent to 59,369 gallons of greywater available at the same 3.2-person average residence. A 32-room hotel would have the equivalent of 593,690 gallons per year. To find out how much you would have at apartment buildings, condominiums, and other multi-family residences, please see our cost benefit analysis. By entering the life-span of the system, you can use that spread sheet to calculate savings over the life of your system. By entering an approximate number of years for a ROI in that same spread sheet cell, and then adjusting those years until the bottom cell equals approximately zero, you can calculate the date of the payback from your system.
Some water districts provide financial incentives for such systems, either in the form of a discount on the new water connection fee or in a water conservation voucher or rebate of some sort. Unfortunately, most water districts still do not have any type of incentive for this. In California, state law requires that the rate they charge must consider the actual amount of water they have to provide.
Waste water reduction comes from the fact that you've reused half the water from inside your residence, or perhaps more from some commercial types of buildings, thereby keeping out the same volume of water from the sewage treatment plant, reducing that plant's cost of operations, mainly by reducing energy demands, and decreasing chemical discharges into the environment. If your home is on a septic system, you reduce impacts to your precious leach fields by up to 50%! This is accomplished by not only removing the sheer volume of water and placing it at the root zones for plant usage, but also by introducing greywater's inherent solids, which are almost exclusively organic, into the upper layer of the soil, which has a high degree of microbial activity. There, indigenous microbes in the soil ingest those solids, producing mainly fulvic and humic acids, which are literally plant food.
Some sewer districts have formal rate reduction schedules for our systems, especially in their commercial rate schedules. All that is usually required for receiving the reduction is a greywater meter and documenting the use for them. Most residential sewer rate schedules are based on your fresh water usage in the supposedly non-irrigated winter months; with that type of rate schedule, the lower your winter water use is, the lower your year-round sewer bill automatically becomes. In California, state law requires that the rate they charge must consider the actual amount and type of wastewater they have to treat.
With a ReWater® system in operation, the laundry surfactants (surface acting agents, molecules which bind to water on one end and oil on the other) found in greywater that normally would have gone to the city sewer plant to ultimately be discharged into the environment are broken down by soil during greywater irrigation. Conventional sewer plants can not break down surfactants. 100% of the science collected from generations of septic tank leach fields proves that soil is the only known method for breaking down surfactants – there is no dispute on the science.
On the other hand, many recent studies, prompted by EPA’s realization that fish living near municipal sewer discharge plumes were sexually mutating, show that the most common types of municipal sewage surfactants mimic the human female hormone, estrogen. In the late 1990s, numerous agencies and universities underwrote studies to see if that was in fact the case, and it is. Those surfactants come mainly from laundry detergents. This particular issue of proven surfactant science is so new it is typically known only to EPA scientists and wastewater and drinking water activists, but because humans can mutate from “gender benders” like estrogen as well as fish, it should be everyone's concern.Return to Top
Irrigation run-off pollution, which contains animal feces, fertilizers, pesticides, and silt, is the single largest source of water pollution in Southern and Coastal California. Our recycling systems use all water underground, eliminating irrigation run-off pollution entirely, helping to keep the landscape's surface dry, which helps stop the initial part of most rain run-off events as well. Builders are under tremendous pressure these days to reduce run-off, and traditional methods of trapping run-off are expensive and land-consuming. Now, there's an inexpensive solution!
A 2005 California Energy Commission report indicates that over 19% of all electricity used in California goes to pumping water around the state. Numerous studies, including one by UCLA Architecture and Urban Planning Professor Murray Milne, 1978, show that at least 25% of all the energy consumed by the "City of Lights", Los Angeles, goes to pumping water there. San Diego uses an even higher percentage than Los Angeles. By reusing half the water from inside a home in southern California as you do with a ReWater system, you've cut down on the energy required for that home by about 12.5%. That's a lot of carbon not floating in the air for us to breathe every day.
When the monetary values of all the benefits from greywater irrigation are combined, greywater irrigation is the least expensive method of water reuse. The State Water Resources Control Board has determined that greywater can cost less than $600 per acre-foot. Most water reclamation projects cost far more than that per acre-foot - their proponents claim they don't, but they subtract the cost of the massive subsidies they are receiving, which the public ultimately pays for, usually through big state water bonds. The real cost of those centralized water projects is actually enormous monetarily and environmentally. For example, compare greywater irrigation to desalinization, which costs over $1,500 per acre-foot, some authorities say as much as $3,000 per acre-foot, all due to increased energy costs.
Because greywater is used in underground drip irrigation systems, roots grow downward to collect it. Thus, plants are stronger and more able to withstand nature's forces when irrigated via a greywater system. By applying water at the surface, sprinklers promote just the opposite effect. Note the remains of a large sprinkler-irrigated tree after a big wind and chainsaw:
Also, greywater contains shampoo, and the most common ingredient in shampoo is ammonium laureth sulfate, which is also sold as a soil conditioner. This ingredient loosens the debris, oils, and dried sweat in your hair, and it loosens the same type of constituents from your soil, allowing the soil to remain open, letting water pass through it freely. Good percolating soil is important for plants, as it allow their roots to grow unimpeded, and to uptake water and nutrients faster.
Water storage projects used to be taken for granted - if a new dam was thought needed, it was built with few questions asked. No longer. Greywater irrigation takes up no additional land and its accompanying flora and fauna, and is less expensive per acre-foot than water storage projects being implemented by public agencies. In the picture below, of Diamond Valley Reservoir in Hemet, California, 800,000 acre-feet of water are stored at a cost of $2.1 Billion ($2,625 per acre-foot), plus O&M. While greywater irrigation doesn't provide emergency storage of drinking water supplies, in the real world where people irrigate landscapes even during water emergencies, greywater irrigation systems do provide a serious and cost-effective buffer in times of need, with no land costs.