Our First Greywater Installation Begins
Last month we got started on our first greywater project, one of Austin’s few whole house residential water conservation efforts to date. This is part one of our coverage on this environmental trendsetter.
While greywater recycling that simply diverts laundry room washing machine outflow from the indoor sewer drain to outdoor distribution has been in use for a long time, whole house efforts that collect and reuse everything but toilet, kitchen sink, and dishwasher output require a carefully engineered approach in order to effectively treat waste that contains concentrated amounts of nutrients, particularly phosphates and nitrogen.
Planning Needed To Avoid Problems Later
Simply collecting greywater without any further action simply turns an experiment into a nightmare, as the oxygen needed for aerobic breakdown is quickly used up while the resulting congealed mess turns into a greasy, smelly scum.
The best way to treat greywater is also the simplest: introduce it as soon as possible into a biologically active layer of topsoil, where naturally occurring microbial activity can begin the process of decomposing the unwanted contents.
The rough-in’s finished. It’s critical that stub outs for hookup are clearly labeled as grey or blackwater – these definitely can’t be mixed!
Our project home will collect all the discharge except for toilet (blackwater) and kitchen/dishwasher waste in a 70-gallon underground tank. From there it’s automatically pumped through an above ground sand filter before being distributed through a drip irrigation system of low pressure emitters.
The end result is an overall reduction in downstream sewage treatment of up to 90%, as water that’s not considered hazardous is recycled rather than adding to the demand of Austin’s rapidly growing population on local plant facilities.
According to Wilson Plumbing General Manager Chris Siebenthaler, “We expect the average amount of reduction from the municipal waste water treatment stream to be between 85 and 90-percent of water use. At the same time, that recycled water will fulfill the owner’s irrigation needs, further reducing demand on our potable water resources.”
The Cost-Benefit Analysis
In addition to reusing greywater for irrigation, the homeowner is also installing a rainwater collection system in the form of seven, 900-gallon tanks, for a total of 6,300 gallons that would otherwise end up as runoff. Together, the two systems – greywater recycling and runoff capture – will significantly lessen the environmental impact of the home’s footprint in terms of water consumption, disposal, and treatment.
In the most basic terms, the home’s owner will significantly reduce both his use of municipal water use and his contribution to the wastewater stream by recycling a big percentage of what otherwise would flow down the sewer and storm drain, and by capturing rainwater runoff to be used in place of treated tap water for irrigation and pool filling.
As for the cost, plumbing during rough-in on new construction doesn’t add that much to the overall budget. The collection, filtration, and irrigation systems, all of which are added after construction’s finished, represent the biggest portion of the overall cost. The good news is that when completed, inspected, and approved, there’s a $5,000 rebate available as further incentive.
In states like California, which are under extreme pressure to reduce consumption because of dwindling resources and growing demand, some municipalities are now requiring that greywater – and even blackwater – recycling be included in new construction. We expect that at some time in the not too distant future Austin will also consider how current and developing technology can be utilized to further help conserve water resources.