section_icon_gw Greywater Frequently Asked Questions


Greywater FAQs

Can greywater be used for drip irrigation?

Drip irrigation tubing has very small emitters, which will quickly clog from particles in greywater. To use successfully use greywater in a drip irrigation system you’ll need to:

  1. Filter it.
  2. Have a plan to clean the filter (either automatically or by hand).
  3. Employ “greywater compatible” drip irrigation tubing.

Keep in mind that greywater filters do not remove salt or other chemicals which may harm plants, the filters remove particles to prevent clogging of outlets. There are two ways to filter greywater: manually cleaned filters and automatically cleaned filters. Manually cleaned filters are lower in cost than automatically cleaned ones, but require frequent maintenance, and thus are often the cause of system failure or abandonment. (Most people find it tiresome to clean a yucky filter month after month, year after year.)

For a long lasting system, it’s best if the filter is automatically cleaned. These self-cleaning filter systems are usually connected to the potable water supply so the pressurized water can “back flush” the filter. Having this connection to the potable water supply creates the potential for “cross contamination” (greywater being sucked back into the potable water from a drop in city water pressure) so a “back-flow preventer” is needed. This adds increased cost and regulatory oversight to the system.

If you want a filtered, drip-irrigation, system we recommend getting a maintenance contract with an installer when ever possible.

There are a few manufactured systems designed to use greywater in a drip irrigation system. See the Manufactured Systems page for more details.


Can I store greywater?

Do not store greywater! Learning to use greywater can feel counter-intuitive because the rules for irrigating with fresh water do not apply. You can store fresh water or rainwater for later use, but greywater should be used as soon as possible after it’s produced. In pumped systems with a temporary surge tank greywater should not stay in it for more than 24 hours. Unlike rainwater and fresh water, greywater has nutrients and organic matter from soaps and dirt. As these start to decompose they use up the oxygen in the water, which begins to smell very bad. It is possible to treat the greywater for storage, but this is impractical in most situations because fresh greywater is generated on a daily basis.

Can I use greywater for a pond, creek, or waterfall?

As greywater is not clean enough for safe human contact, it should not be used directly for a pond or any other type of water feature (fountains, waterfalls, creeks, etc.). A pond of greywater will not only smell bad, it could be a health hazard if someone, like a child, played with it and drank it. For greywater to be utilized in a pond or other water feature it needs to be treated first, such as with wetland plants. Because wetland plants evapo-transpire water, there will be less water to use in the pond. In most yards, there are other plants that need irrigation, and greywater can simply and safely be used directly to irrigate them, then less fresh water can be used for the pond since it won’t need to travel through a wetland first. If there is no other need for irrigation, greywater can be treated with wetland plants and then used to create various water features. (note: this type of system will be more difficult or impossible to get a permit for.)

Can I use greywater if I have a water softener?

Most water softeners use salts to bind with the metals in the water and make the water “soft.” This kind of water is not suitable to be reused outside as it is high in salt and can harm plants and soil. Alternatives to sodium water softeners are potassium softeners. Depending on the level of hardness and the way the water softener system is set up, some people are able to bypass their washing machine from the softener and then reuse that portion of their greywater. There are other options for softening water, such as magnets. We have no personal experience with magnets, and would like to hear from anyone who uses them.

Can I use the water from a dishwasher?

Dishwashers are not usually a good sources of greywater because the detergents for dishwashers are typically high in salt, which is harmful to plants and soils. If you are able to find a dishwasher detergent that does not have salt or boron in it, then the greywater can be reused. If you don’t have a sewer/septic option, and can’t find “plant friendly” detergents, direct greywater to a dedicated portion of the yard and plant with salt tolerant plants. If your state doesn’t consider kitchen water “greywater,” than a system using dishwater water will not be code compliant.

Do I need to use traps and vents in the greywater plumbing?

When ever possible, greywater should be diverted downstream of the fixture’s p-trap and vent (this is also required by most codes). In some situations it’s much more convenient to install the diverter valve before the p-trap and vent, and it’s safe to do so, here’s why:

In standard plumbing, drain flowing to the sewer/septic system needs a P-traps to prevent sewer gasses from coming up the drain and into the building. However, when a diverter valve is installed in the drain and the sewer/septic side is turned “off” (directing water to the greywater system) the sewer connection is physically blocked by the valve, preventing any sewer gasses from passing it. In this situation no P-trap is needed on the greywater line.

It’s common in a sink greywater systems to install the valve (and divert the greywater flow) in the trap arm of the sink, so that the user can control the flow of greywater from inside the home.

Vents release gasses from the sewer, prevent the water in the trap from being siphoned out, and help the water flow down the drain. All standard fixtures need a vent, but the greywater side of a diverted drainline can operate safely without one, because there are no sewer gasses. If you have a greywater line with no vent you may have slower draining and hear gurgling, but it will still function.

How can I protect the public health while using greywater?

There are three things to keep in mind to protect public health when using greywater.

  • Do not allow greywater to pool or pond; this creates habitat for mosquitoes and a place for people to contact the water.
  • Ensure greywater soaks into the ground and does not run off into neighboring properties or places people could contact it.
  • Don’t put greywater onto the edible portion of plants. Greywater should irrigate the roots, not be sprayed or dumped onto the plant itself. Greywater is not safe to drink, and thus should not touch the part of a plant someone would eat.
  • Do not create a “cross-connection” with your system. The greywater system should be totally separate from any potable water system. For more complex systems that supplement greywater with either rainwater or municipal water, the system requires cross connection protection of an air gap or other approved device (for example, and RP).


How can I work with my local building department to make permitting greywater systems easier?

If you live in a state with an existing greywater code that allows for simple, affordable systems, focus your efforts at getting a streamlined permitting process and working through barriers people encounter when they try to install a permitted system. If your state has had a recent state code change you can work to gain buy-in and implementation at the local level. Go through the permitting process yourself, or work an ally in your town, for example a green-minded council member or someone in the water agency. Work with the permitting agency (eg. building department) to create a simple permit application and check-list so the process is easier for future systems.

In states without a greywater code you’ll need to focus efforts at the state level: local regulators are hesitant to allow anything not explicitly allowed by the state.

Keep in mind that many local inspectors and health officials have no direct experience or training with greywater systems and their job is to both protect public health and to protect their agency from liability. Because of this, they may not be enthusiastic about permitting greywater systems if there are not many existing permitted systems in their jurisdiction. Even in states with “greywater friendly codes,” like Arizona, New Mexico, and Texas, and (for some types of systems) California, officials may not be familiar with the code. In your conversations with your local officials, it may be helpful to share permitted project examples from nearby places.

In states without codes, or with restrictive codes, the vast majority of people who want a greywater system install it without a permit. It is possible to ask for an “Alternative methods and materials” permit, which is intended to allow for new or alternative systems not covered under the current code. You could offer your “experimental” system to be monitored by the city, which could help them learn more about greywater systems and feel more comfortable allowing future systems.

If you need a permit for your project it’s better to contact the building department first, and explain to them what you’re trying to do and find out their concerns, that way you can present a design that will address their concerns.

See the Code and Policy page for more information.


How do I become a greywater installer?

To become a greywater installer, you need a combination of ecological landscaping/permaculture training and basic plumbing skills. There are many ecological landscaping training opportunities from Green Garden programs, Bay Friendly Landscaping, and others. For related skills, many excellent permaculture trainings are offered across the country, like at the Occidental Arts and Ecology Center. Community colleges and trade schools offer classes in basic plumbing skills. Hands-on experience and mentors are important, too. Greywater Action teaches a 5 day course for people wanting to be greywater installers.

How do I flush my toilet with greywater?

There are some simple, economical ways to flush a toilet with greywater. Here are two we recommend.

Easiest way: The bucket flush method. Lift the lid of the toilet. Dump greywater directly into the bowl. This will create a siphon affect and the contents of the bowl will empty.

Or, install a simple system like Sink Positive, a toilet lid with a faucet: flush water flows through the sink lid so you can wash your hands in the water as it fills the toilet tank.

Most other systems for flushing with toilet water are manufactured greywater systems, or high end systems. These systems are costly, economically and environmentally, as they rely on pumps, and chemicals or electricity to function. We discuss manufactured systems to flush toilet more here.


How do I protect the environment while using greywater?

There are two main rules to follow to protect the environment.

  • Send nothing toxic down the drain.
  • Do not allow greywater to enter a fresh water source, like a creek, stream, or river, or high groundwater table. Biodegradable material will compost on the land, but will contaminate a creek. Nutrients will fertilize plants on land, but will cause algae to grow and rob water of oxygen, harming aquatic organisms.
  • Use biodegradable products that are salt and born free (which harm plants and the soil)
How do I siphon water from my bathtub?

A siphon uses gravity and atmospheric pressure to move greywater outside. In order for this to work the landscape outside must be lower in elevation than the bottom of the tub. There are several ways to siphon greywater out of a bathtub. You can also read an article from Grist that shares several products on the market for siphoning.

  1. Use a hand pump to start the siphon. Find a pump at a marine supply house, from Grainger, or possibly a hardware store.
  2. Purchase a product made for this application. Siphon Aid is one.
  3. Start the siphon with the bathtub faucet. Here’s how. Get a hose or tube long enough to run from the tub, out an open window/door, and down to the landscape. Put one end of the hose on the faucet, cup your hand around it to force water from the faucet into the hose. Once the hose is filled with water drop it into the tub and the siphon effect will pull water from the tub outside. The product Siphon Aid fits snuggly onto the faucet making this method for siphoning bathwater a lot easier.


How do I use greywater if my house has a concrete slab foundation?

Access to greywater can be lost when pipes enter a concrete slab foundation. If your house is on a concrete foundation you still have some greywater options.

  1. Use the greywater from your washing machine, as you can access it with out needing to alter the plumbing.
  2. Use greywater from sinks. It is often possible to attach a 3-way valve to the trap arm of your sink, enabling you to send the pipe outside before it enters the cement foundation. This breaks some of the conventions of plumbing, but is fine to do in practice. The greywater side is not connected to the sewer, so no trap or vent is needed (all drains have traps on them that have standing water to prevent sewer gasses from entering the building.
  3. Elevate a tub or shower to access the plumbing.
  4. If there is a second floor, use the greywater generated from there.
How much does a greywater system cost?

The cost of greywater systems varies on how simple or complex it is to alter the plumbing, how large the yard is, and who is doing the installation. For simple systems much of the work is digging; digging mulch basins and digging trenches to bury pipe. If you’re on a limited budget labor costs can be reduced if you are willing to do much of the digging yourself, or find some eager friends or family who want to support greywater installations (and learn in the process).

These are rough average costs, exact costs will vary depending on the size and complexity of your site.

  • Laundry to Landscape
    •  Materials only $100-$250
    • Full installation $700-$2,000
  • Branched drain
    • Materials only $200-$400
    • Full installation $800-$3,000
  • Pumped system
    • Materials only $400-$600
    • Full installation $1,000-$4,000
  • Automated pumped system for drip irritation
    • (High-end residential) $5,000-$20,000
How should I use filters?

The most effective greywater “filter” is biologically-active soil covered in mulch! In simple systems, filters usually cause more problems than benefits. Filters need regular maintenance–not a fun job–and if the filter isn’t changed the system will fail. Filters remove large particles (hair, lint, etc), but not salt or dissolved chemicals. If you design your system in such a way that large particles won’t clog the system, then you don’t need a filter: Design so that larger particles in the greywater will be caught in mulch and compost, while the water soaks down to the dirt and irrigates the roots of plants. We recommend systems with no filters other than well-mulched soil.

High tech systems (into drip irrigation or for toilet flushing) do require filters. These systems need automatic cleaning of the filter to be long lasting.

We discuss several systems that filter greywater to be used for irrigation or toilet flushing on the Manufactured Systems page.


How should I use my pump?

The longest lasting, lowest-maintenance, most ecologically sound systems will not require a pump. If you can, use gravity to irrigate with your greywater! Make sure your system truly requires a pump before deciding to use on.

These situations do require a pump:

  • The only landscaped area needing irrigation is uphill of the greywater sources.
  • There is a long flat area of hardscape that must be crossed before reaching the landscape.
  • The yard is flat and the only irrigation needs are far from the house.

If you have to use a pump, look at the closest places you’ll need the water and then pump the greywater there. You never want to pump more than you need to (ie. don’t pump to the top of your property, or to your roof) If you pump to a high point and then gravity drain to the yard, it uses extra electricity and will be harder to control the flow of water to the plants. Pumps pressurize water and make it easier to spread the water out to plants; this benefit is lost if the system switches to gravity flow.

How to Choose a Pump

Look for an effluent pump that’s rated to pump 3⁄4″ solids (so it can pump out anything that gets down the drain), is fully submersible, and operates on 115/120-volt (not 230/240-volt) electrical power. A typical sump pump is not powerful enough for this system. Some people use smaller-sized pumps, rated to pump 3 ⁄ 8 ” or 1⁄2″ solids, though they aren’t as strong as 3⁄4″-rated units.

Is greywater legal?

Greywater policies differ state to state. Currently, the best policy is for the state of Arizona. They have greywater guidelines to educate residents on how to build simple, safe, and affordable, greywater irrigation systems. If people follow the guidelines their systems falls under a general permit and is automatically “legal”, that is, the residents don’t have to apply or pay for any permits or inspections. California had the first greywater code in the nation, but it had been very restrictive and usually made it unfeasible for people to afford installing a permitted system. Because of this the vast majority of systems in California are unpermitted. Using data from a study done by the soap industry, Art Ludwig estimates that for every permit given in the past 20 years, there were 8,000 unpermitted systems built. In 2009 California changed it’s code, making it much easier for people to build simple, low cost systems legally. Washing machine systems that do not alter the house plumbing can be built with out a construction permit so long as 12 guidelines are followed. Read more about codes and policies here.

What if I’m on a septic system?

Greywater, especially from the washing machine, is often kept out of the septic system to extend its life. Diverting some greywater from failing septic systems can be helpful and is a common practice in rural areas. Additionally, there are systems that can transform water inside the septic tank into irrigation quality water, which can be sent through a drip irrigation system. One such systems is called Sludge Hammer.

What should I communicate to my plumber?

A standard plumber has the skills to perform the inside portion of your greywater system. They have the skills to cut in a 3-way diverter valve to the drain pipe of your showers or sinks, and can send the pipe outside. However, most plumbers are not familiar with 3-way diverter valves because they are typically used for swimming pools, and so may want to use another method of greywater diversion. We advise you to request a 3-way valve as it’s the easiest for the user.

Many plumbers do not have landscaping skills, nor experience with greywater, and may not feel comfortable or interested in the outside portion of your system.

If working with a conventional plumber for the inside portion of your system there are a few things to talk with them about.

  1. Conserving elevation. Keep the greywater pipes as high as possible so they can exit the house over the foundation.
  2. Keeping the greywater separate from the blackwater until the greywater pipe exits the house. There is no need to plumb the greywater and blackwater in separate pipes (“dual plumb”) all the way to the main sewer line.
  3. Installing a 3-way valve to capture the greywater in a readily accessible place. You can show your plumber diagrams such as these to explain what you need: (from the book, “Create an Oasis with Greywater” ) Diagram 1   Diagram 2

A word of caution:

If you are sure you want a simple system be sure to communicate that to your plumber (or contactor). Some plumbers or contactors who haven’t had much direct experience with greywater systems may have a tendancy to create an overly complicated system that probably won’t work as well, or will take more maintenance than a simple system. It won’t hurt to ask if they have a greywater system in their own home!

What soaps and products can I use with my greywater system?

Plant friendly products are key when reusing your greywater. All products should be biodegradable and non-toxic. In addition, they should be low in salts (sodium) and free of boron (borax), two common ingredients that are non-toxic to people but are harmful to plants and/or the soil. Chlorine bleach is also harmful to plants and should be diverted with any other harmful products to the sewer or septic by switching the 3-way valve. Hydrogen peroxide bleaches are less harmful and can be used instead of chlorine. Another consideration with soaps and products is their affect on the pH of the water. While many soaps do not change the pH, some do. In general, liquid soaps do not change the pH, while bar soaps make the water very basic (opposite of acidic). Certain acid loving plants may not be happy with this kind of water. If you’re uncertain if the pH is being affected choose plants that are not acid loving to irrigate. Acid loving plants include ferns, rhodedendrons, and blueberries.

Products we recommend: (they are low salt and boron free, and pH neutral)

  • Laundry: Fit Organic, Puretergent, Oasis, Ecos, Biopac liquid detergent, Trader Joes liquid detergent, Vaska. There are also soap alternatives that are greywater friendly, like soap nuts, ozone treatment systems, and “wonder balls”.
  • Showers:  In a shower, shampoo is fairly diluted so it is not as important as in the washing machine to have the best products, but it is important to have products that are not harmful to our health, surprisingly many shampoos and conditioners contain carcinogenic chemicals. You can find out what’s in your products at the Campaign for Safe Cosmetic’s on-line database.
What’s different between designing a greywater system for a new construction vs. a remodel or retrofit system?

If you’re building a new house, or doing a full plumbing remodel, you may want to combine all your greywater into one line, and then have a collection tank and pump to distribute it more widely to your landscape.

In retrofit situations it doesn’t usually make sense to combine all the greywater pipes together because it can be very costly. Usually it’s more practical to do each fixture separately and use that water to irrigate the area closest to the fixture.


Which plants should I water with greywater?

In a simple greywater system you want to find a balance between the amount of greywater generated and the water requirements of the plants you’ll be irrigating. Since both these amounts fluctuate, the optimum design strikes a good balance. You want to keep the plants healthy while irrigating as many as possible (to save the most water possible).

Larger plants are better suited to be irrigated with a simple greywater system than smaller plants. Choose the larger plants, such as trees, bushes, berries, shrubs, and larger perennials or annuals. (It’s much more difficult to water lots of small plants that are spread out over a large area with simple greywater systems.) Be sure to use “plant friendly” products in the house, those free of boron and low in salts, then greywater is suitable for any plant that wants to be irrigated. Read more about plants and greywater on the plant page.

Will a laundry to landscape system hurt my washing machine?

A properly designed laundry-to-landscape system should neither harm a washing machine nor cause it anymore wear and tear than normal use. Factors such as washing machine variation and landscape differences result in no two systems being alike. Hence, recommendations for how to design a safe system do not guarantee that they are safe for your particular washing machine. Based on our experience, however, we have not encountered problems with any properly designed system for any washing machine.

Assuming that your washing machine’s pump is not worn out, laundry-to-landscape systems that follow these guidelines should not exceed the manufacturers recommendations for the pump.

  •  Use 1″ tubing on the main line (nothing smaller).
  •  Do not plug the end of the main line. If the 1/2″ outlets begin to clog a plugged end will restrict the flow of greywater and cause back pressure on the pump.
  •  Do not pump uphill. If your landscape is slightly higher than the washing machine, place a platform under your machine. If your landscape is uphill from the house, you will need to incorporate another pump into the system.
  • Do not travel more than 50 feet across a flat yard. Pushing water through a horizontal run of pipe adds strain on the pump. Depending on how many gallons per minute your machine pumps out, 50 feet is typically the same as pumping water up 1.5 to 3 feet.
  •  Do not install a laundry to landscape system if your machine has existing problems such as the water does not drain completely.

If your washing machine’s pump is struggling, or the water does not drain properly, the most common cause is a clogged pump filter. This filter catches all the large particles – coins, trash, paper clips, and so on – that get into the machine from the laundry. If the filter is clogged, the pump has to work harder to push the water through the debris. A good habit is to check the pump filter and clean it out on a regular basis. Here’s one example of how to clean a pump filter.

In his on-line book “Graywater Gardening,” the owner of a greywater company claims that laundry to landscape systems have broken washing machines in Australia. However, this claim is hearsay because he has never actually seen any of these systems or broken machines. Furthermore, there is a conflict of interest because his solution to the “problem” of laundry to landscape systems harming washing machines is the greywater system he is selling.

Will a laundry-to-landscape system void any warranties on my washing machine?

Warranties vary from company to company and policy to policy. Based on anecdotal evidence and conversations with people who have installed a laundry-to-landscape system, a washing machine’s warranty does not seem to be affected. If washing machines have required maintenance, the repair people have not attributed the problem to the greywater system. On newer machines the problem is usually electronic or a clogged pump filter. For individuals with existing laundry-to-landscape systems who have purchased a new machine, the company installer has disconnected and then reconnected the laundry to landscape system for them. We’ve only heard of one instance when a washer installer didn’t want to hook up the new machine to the diverter valve, saying it would void the warranty. In you have bought a new machine, make sure the connection the installer makes does not leak because they may not understand fully how the hose should be connected to the system.