Laura Allen remembers getting her first water bill. She was in her early 20s, sharing a California house with some friends, and they’d just planted a garden at their new home. When the bill came, it shocked them; the tab was much higher than they expected.“That bill sparked questions for us,” she says. “It really caused us to think more about our water use and consumption, and to realize that we could be using it in smarter ways.”

Fortunately, Allen, who would later become a leading expert on graywater irrigation, just happened to be taking a plumbing class at the time for her own edification. “That was why we felt empowered to do something,” she recalled. She attached a pipe to the washing machine to direct its wastewater to the garden — an illegal act, at the time — and her very first graywater system was born.

Allen and the collaborative she later founded were instrumental in getting graywater legalized in the state. Now, almost 20 years later, she leads Greywater Action, a group that offers graywater-system installation workshops and helps develop graywater codes and incentives across the country.

Graywater irrigation is not only a West Coast thing. Over the years, Allen has noted increasing interest from landscape contractors all over the country who want to learn how to install these systems. One state is even making graywater reuse a building requirement. In February 2017, Hawaii began specifying graywater reuse systems in all new construction projects.

“Any professional who wants to stay current, who wants to be part of the solution, who wants to offer positive options for their clients — graywater’s really attractive to that type of landscaper,” Allen says.

Living in regions experiencing long periods of drought, such as Texas or California, coupled with tightening water restrictions, has heightened people’s interest in graywater. Bob Hitchner, chief sales and marketing officer for Nexus eWater, notes, “People understand there’s a value in having their own source of recycled water on-site.”

Leigh Jerrard owns Greywater Corps, a company that designs and installs graywater systems in Los Angeles County. He’s noticed a definite uptick in business since starting the firm eight years ago. “We had four or five years of drought, and so people became very conscious about water conservation.”

Even after the California drought was declared over in early 2017, concern about climate change and fear of future droughts has kept consumer interest high. The recent, devastating wildfires may become another factor, if people start thinking that graywater irrigation might help keep their landscapes wetter and more fire-resistant.

The western drought caused many small businesses to spring up around graywater system installation. “In the retrofit market, there are companies very focused on providing graywater solutions for residential use,” Hitchner says.

Graywater irrigation for both residential and commercial applications is a relatively new industry with room for more players. It’s gaining more visibility, even popping up in some unusual places. For instance, the Half Moon Bay Brewing Co. in California raised eyebrows in 2015 when it unveiled an India pale ale made with treated graywater.

This certainly appears to be a trend that will keep growing, and it presents an exciting opportunity for contractors who want to get in on it while the industry is still pretty much on the ground floor.

Learning how to install graywater systems can be a great way to grow your business while at the same time, help conserve our most precious natural resource. “I think it’s still a very specialized market,” Hitchner says. “The question landscape contractors should be asking is, when do they need to get into this market, and how?”

The basics

Graywater is non-potable wastewater from washing machines, showers, bathtubs and bathroom sinks. This water can be treated or untreated before it’s reused. Treated graywater can be stored indefinitely, while untreated graywater must be dispersed within 24 hours because of anaerobic bacterial growth (and, not to mention, some funky smells). Most graywater systems use untreated water.

It shouldn’t be confused with reclaimed water, partially treated wastewater that also can’t be used for drinking, but may be used on landscapes. Many municipalities use it to irrigate public golf courses. Reclaimed water flows through the same purple PVC pipes used for graywater.

Nor should graywater be mistaken for blackwater, which is what’s flushed down toilets. That is never allowed to go anywhere but the sewer. Many states classify kitchen-sink effluent, because of its high bacterial count, as blackwater; others consider it graywater.

If you’re seriously thinking about making graywater system installation a part of your business, the first step is to check your local laws and ordinances. “Regulations vary from state to state and can be dramatically different across state lines,” cautions Allen.

Make sure you don’t run afoul of your local water district or health department. In some states, anything more complicated than a simple laundry-to-landscape system will require a permit, because you’ll be altering a building’s plumbing system.

Your local water district may be offering financial incentives that’ll be an extra selling point for your customers. In Cupertino, California, for example, up to $400 is available in rebates to cover the cost of materials. In Tucson, Arizona, owners of single-family residences who install permanent graywater irrigation systems will be reimbursed up to $1,000 in costs.

If you’re going to install graywater irrigation systems, you’ll also need to know how to install subsurface drip. Because of the presence of bacteria and trace amounts of fecal matter in bath and laundry graywater, it’s almost always against the law to distribute it though conventional irrigation systems using rotors or spray heads.

The spray nozzles aerosolize the droplets, which then could be breathed in by children, the elderly, or people with compromised immune systems. Pooling and runoff of graywater is also prohibited for the same reasons.

Calculating a solution

Once you’ve checked the guidelines governing graywater reuse in your area, it is recommended to talk to your clients to find out exactly what they expect to get from such a system. Using graywater in this way is still a new concept for many so it may be important to educate your clients.

“Sometimes people think they’re going to get something like a spigot outside that they can just connect a hose to, and water with graywater instead of the tap,” Allen says.

“That’s not at all how it works.” She advises system installers to discourage unrealistic expectations by being clear in the initial consultation.

The next step involves asking some basic questions about the residents’ habits. How many times a week is laundry done? How many people live in the house? How many baths or showers do they usually take in a week?

“We call these ‘personal calculations,’” says Allen. The national average for water usage is 17 gallons per person per day, but every household is different. Doing these calculations will help you determine how much graywater will be available for irrigation.

Another personal calculation, especially for residential clients, involves determining how much they’re willing to change the kind of home cleaning, laundry and personal hygiene products they use. For instance, many laundry detergents contain large quantities of sodium, chlorine or boron. “All of that is eventually going to end up in the soil,” Jerrard said. “It’s not going to kill the plants immediately, but over several years, you’ll get a buildup of salt and other substances.” On the other hand, the phosphorus in laundry soap is beneficial to plants.

Specially formulated laundry detergents and other soap products that are safe for use with graywater systems are available, but a consumer may have to do some hunting to find them. Shampoos and body soaps are less concerning. “But we do want people to pay attention to what goes down their drains,” continues Jerrard. “I would argue that if you’re afraid to put it in your dirt, you should be afraid to put it on your skin.”

Plant choice will also be affected. Graywater irrigation is well-suited to fruit trees, shrubs and bushes, according to experts, but acid-loving, pH-sensitive plants such as blueberries, ferns, camellias and rhododendrons call for pH-neutral soaps and detergents. Also, untreated graywater should never come into contact with any of the edible parts of edible landscaping plants. But that shouldn’t be a problem when irrigating with drip, which is usually the only method for distributing graywater.

Established lawns aren’t well-suited to graywater irrigation because of the aerosolization problem, unless retrofitted with subsurface drip.

This could be a good time to broach the subject of replacing the turf with drought-resistant plantings that could then be drip-irrigated with graywater. In general, though, graywater irrigation is confined to shrub and flower beds.

Types of systems

The three major types of graywater systems are: laundry-to-landscape, branched-drain and pumped. All of them are set up similarly to modified drip systems. One-inch piping with half-inch outlets should be used to direct water to the plants. However, emitters or tubing less than half an inch in diameter should be used to avoid clogging. Putting a filter in at the connection point is a good idea, for the same reason.

A laundry-to-landscape or L2L system is one of the most popular and easy-to-install systems. A washing-machine discharge hose is hooked directly to a three-way diverter valve that allows the laundry water to be sent to the landscape, or to the sewer or septic system. For instance, if someone does a bleach load, or washes diapers, that water needs to go directly to the sewer system. The only catch is that the homeowner must remember to flip the diverter lever over each time.

A shallow trench must be dug for the pipe that will channel the laundry water to the plants. “Because you’re relying on the washing machine’s discharge pump to push the water out, you have some flexibility as to where you can direct it,” Allen says. About 50 feet of distribution is achieved on flat areas and more if the water courses down a slope.

Branched-drain systems are a bit more complicated to install. These send bath and shower water through 1.5-inch standard drainage pipes and divert it to the landscape through a series of increasingly smaller pipes or branches. To install such a system, you’ll need access to the plumbing pipes. Check local ordinances before you start; some states mandate that a licensed plumber do this part of the installation.

In a house or building under construction, installing a brancheddrain graywater system is pretty straightforward. Most of the time, though, you’ll be dealing with retrofits, and plumbing challenges may be encountered, especially with bathrooms.

Most plumbers will connect all the bathroom drainpipes — shower, bathtub, sinks and toilets — to one outflow pipe. But for graywater, two pipes will be needed. One pipe will take the toilet effluent to the sewer, and the other will funnel the tub and sink runoff to the graywater system. “We call it ‘dual plumbing,’ where you basically have two networks of drainpipes underneath a house,” Jerrard says.

The branches should terminate in a mulched landscape bed or mulched basin around a tree, shrub or other large perennial. The mulch will help biodegrade any solids present in the water. Flow splitters will help ensure even distribution.

“The wood chips perform several functions, including preventing runoff by containing the graywater and allowing it to percolate out laterally, soaking the wood chips and spreading it throughout the mulch bed,” says Jerrard. Up to eight mulch beds can be irrigated at a time.

Branched-drain systems depend on gravity, so pumps aren’t required. But the property’s grade has to slope down by at least 2 percent. These systems require more trenching and design work, but once they’re installed, are easy to maintain. “There are no moving parts,” says Allen, “so there’s nothing to break. These are really great systems.”

A pump system is used when a landscape is uphill from, or a good distance away, from a structure. The graywater can be directed to a temporary storage tank for later distribution (within 24 hours).

A more advanced pump system may include a filter, and regular maintenance will have to be done to manually muck it out. This cleaning process is critical. “A filter is designed to capture particles, but if they aren’t cleaned periodically, the whole system will eventually fail,” says Allen.

Some of these more advanced systems feature self-cleaning filters that use either compressed air or a potable water source to backflush debris out of them. However, introducing a potable water source to a graywater system creates the potential for a cross-connection, which should be prevented at all costs. Toavoid contamination, it is advised a backflow device be incorporated.

More advanced — and much more expensive — systems are available that work like small water treatment plants. The treated graywater they produce can then be stored indefinitely, and, in some areas, distributed via spray nozzles. These types of systems are more challenging to install, and come with strict guidelines.

Experts are predicting a much drier future worldwide. That makes efficient irrigation a must-do moving forward. As irrigation professionals we are uniquely positioned to provide our residential and commercial clients with sustainable solutions that conserve both water and money.

The author is marketing coordinator at the Irrigation Association and can be reached at