Greywater is household water collected from sinks, washing machines, and showers that can be reused for landscape irrigation. Here’s what to consider before converting your plumbing.
Water from bathroom sinks, bathtubs, showers, and washing machines is classified as greywater and, depending on local and state regulations, can be diverted to irrigate landscaping. The water that dishwashers and kitchen sinks produce, on the other hand, can be contaminated with food and can’t be used in greywater systems. Toilet water is off-limits as well.
A simple, low-tech greywater system can be professionally built for $1,000 to $2,000 by installing a three-way valve to funnel water from a washing machine to a hose or pipe that disperses it to the landscaping. More elaborate setups can cost about $10,000 and reconfigure a home’s plumbing to redirect water from bathroom sinks, bathtubs, showers, and the laundry that would otherwise drain to a sewer. The greywater is sent to an irrigation system, sometimes equipped with a pump, to distribute it to plants and trees throughout a yard. Given that complexity, it’s advisable to hire a company that specializes in installing greywater systems and designing irrigation systems.
Whole-home systems can save 10,000 gallons to 50,000 gallons of drinking water a year. Those savings provide a hedge as climate-driven droughts become more intense and frequent. In California, for instance, outdoor irrigation accounts for as much as two-thirds of water consumption in single-family homes. During the state’s record-breaking drought, some utilities and municipalities have imposed water restrictions and steep fines for violating rationing; greywater helps keep plants blooming without blowing your water budget.
Greywater presents some challenges. It can’t be saved for later, as it contains nutrients from soap and detergents that if stored break down and emit a foul odor. That’s a problem when homeowners go on vacation: Greywater stops flowing, and the garden goes dry.
Soap and water nutrients also clog drip irrigation systems, so using untreated household water requires the installation of dedicated lines to distribute the greywater. One solution: adding filtration that allows greywater to be piped into a home’s existing irrigation system. Then when you’re gone and not producing greywater, the irrigation system can tap municipal water.
Greywater does require certain landscapes, and so people have to be willing to say goodbye to the lawn and embrace trees and native and drought-tolerant plants, says Laura Allen, co-founder of Greywater Action, an educational organization in the San Francisco Bay Area.What on Earth?
Regulations generally prohibit using greywater in conventional sprinklers that spray lawns with jets of water. If homeowners want to retain their thirsty turf and use greywater, they must either hand-water the grass or install a drip tubing system beneath the lawn. Experts say replacing a lawn with drought-tolerant landscaping is the best way to slash water consumption. Cities in dry regions often offer subsidies to finance such conversions.
Greywater is particularly well-suited for irrigating trees, shrubs, and other larger plants, Allen says. Fruit trees in particular tend to thrive on the nutrients in greywater. It can be used in vegetable gardens, but, because contact with the edible parts of plants must be avoided, greywater shouldn’t be applied to root vegetables such as beets, carrots, and onions. (You can still grow those veggies by irrigating them with fresh water.) Be sure to use plant-friendly biodegradable soaps and detergents that are salt-free.
Rules governing the use of greywater vary by state and locality.
Regulations are getting better overall in dry states and states that have experienced water shortages, and generally speaking, Western states have updated regulations to make greywater legal, Allen says.
In California and some other Western states, installing a simple laundry-to-landscape greywater system can be done without a permit as long as the homeowner follows health and safety guidelines. Reconfiguring plumbing for a greywater system usually does require securing a permit.
Greywater can be a challenge in the Midwest.
Many of those states don’t have any legal pathways for greywater systems, Allen says.
She also notes that many water utilities in Western states offer rebates and other incentives to offset the cost of installing greywater systems.