Frequently Asked Questions
What is greywater?
Greywater is the water generated from the use of the shower, bathtub, hand sink, laundry, kitchen sink, and dishwasher.
Is greywater different from wastewater?
Yes. Household wastewater, also known as sewage, is composed of two distinct sources:
“blackwater” is wastewater contaminated by feces or urine, and includes wastewater arising from toilet, urinal, or bidet.
“greywater” is the remaining wastewater coming from the laundry, bathroom and kitchen.
Why should I reuse greywater?
Greywater is a significant water resource, provided it is managed in an environmentally responsible manner, and public health and the health of the household are protected. By capturing greywater and using it in an appropriate manner as an alternative to your water supply, you can reduce your water consumption. Your water account will reflect this reduction in water use and there will also be positive environmental outcomes.
Is greywater safe ?
Yes, If greywater is handled properly, not stored, or sprayed its very safe, there are eight million greywater systems in the US, being used by 22 million users. In 60 years, there has been one billion system user-years of exposure, yet there has not been one documented case of greywater transmitted illness.
How can I reduce the risks associated with greywater reuse?
The following measures will reduce the health and environmental risks associated with the use of greywater;
• do not use sprinklers to distribute greywater;
• use subsurface irrigation systems;
• do not spray greywater directly onto food plants;
• do not use greywater on lawns.
• do not allow greywater to enter the stormwater system;
What about kitchen sinks and dishwashers?
These sources produce a kind of difficult greywater because of the heavier amount of food particles. Extra effort must be made to create a very direct steep flow to avoid any clogs.
Often only one side of the kitchen sink is captured that leaves one side going to the septic system.
Do I need a plumber?
If your greywater system requires connection to the sewage system, i.e. to the pipes below your sinks, shower or bath, a licensed plumber should do this work. Its best to use a plumber familiar with greywater so they can work to make the system work as well as possible
What soaps are best for greywater systems?
Plant friendly products are key when reusing your greywater. All products should be biodegradable and non-toxic. In addition, they should be free of salt (sodium) and 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 cleaning and beauty 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 salt and boron free, and pH neutral)
Laundry: Oasis, Ecos, Biopac liquid detergent. There are also soap alternatives that are greywater friendly, like soap nuts, and "wonder balls".
How much does a greywater system cost?
The cost of greywater systems varies on how simple or complex the plumbing is, how large the yard is, and who is doing the installation. On the low tech systems much of the work is digging, digging mulch basins and digging trenches to bury pipe.
These are rough average costs for materials for low tech systems, not including labor.
Laundry to Landscape- $250-350
Branched drain- $300-500
Pumped system-very expensive, and aren't usually recomended for residential systems.
For the low tech systems labor costs are usually a few hundred dollars and could go up to a thousand dollars in larger, more complicated situations.
High-end, high tech, residential greywater system costs
Sand filter to drip irrigation: $5,000-10,000 depending on complexity of the plumbing and if there is a compatible existing drip irrigation system. (including labor, these systems are not easy to do yourself)
What about filters.
The most effective greywater "filter" is biologically-active soil covered in mulch! In low tech 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.
Can greywater be used with drip irrigation
Drip irrigation requires very clean water without particles in it. The emitters for a drip system have very small openings, and will be quickly clogged from the hair, lint, food, and other gunk in greywater. To make greywater compatible with drip irrigation it must be well filtered. (note: these filters don't take out salt or chemicals, only particles.) To work well, the filter for the system must be automatically cleaned. If a system relies on a person to remember to clean or change the filter and they forget, then the entire drip system can be ruined.
To prevent possible "cross contamination" (greywater being sucked back into the potable water from a drop in city water pressure) a "back-flow preventer" is needed. These systems require a pump, electronic controllers, and a backflow preventer (to protect the city water supply).
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. Greywater should be used immediately as it's produced, and if the system has a temporary surge tank the 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.
Which plants should I water with my greywater?
Low tech, simple greywater systems are best suited to water distinct plants. It's usually easy to water trees, bushes, berry patches, shrubs, and large annuals. It's much more difficult to water lots of small plants that are spread out over a large area. Many kinds of fruit trees do prefer deep waterings and then having the soil dry out. Incorporating different "zones" into the GW system allows for this. You can alternate between a groups of trees every other week. Some kinds of trees are fine and happy getting watered all the time. It will also depend on the drainage of your site. A percolation test should be performed to see how well water drains in your site, this will also determine how much you need to spread out the greywater so there is not pooling or runoff.
Read more about plants and greywater on Greywater Action's plant page.
Is greywater legal? YES new legislation here >> New Greywater Policy
Greywater policies differ state to state. The best policy was for the state of Arizona. They have greywater guidelines to educate residents on how to build simple, safe, efficient, 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. This code is now entering the public comment period and will be finalized at the end of 2009.
You can read the CA code here>> New Greywater Policy
Do I need to use traps and vents?
When ever possible, greywater should be diverted after the P-trap and vent. At times, you may find that is difficult or impossible to do. For functionality, P-traps and vents are not always needed for greywater, though systems that do use standard P-traps and vents will not be code compliant. P-traps are needed for any pipe connected to the sewer. They prevent sewer gasses from coming into the building. If you have a 3-way diverter valve on your system and the valve has turned the greywater side ON, and the sewer OFF, then no gasses can come into the house because the valve blocks off the sewer connection. In this situation no P-trap is needed on the greywater line. This situation occurs at times in kitchen sink installations where the 3-way valve is added to the trap arm of the sink. 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 drainline can operate with out 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 do I become a greywater installer?
The skills needed to be a good greywater installer are a combination of ecological landscaping/permaculture and basic plumbing. 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 program for greywater installers. See the installer's page for more info.
How can I work with my local building department to ease legal greywater reuse?
Many local inspectors and health officials have no direct experience with greywater systems, and often little training. Their job is two-fold: to protect public health, and to protect their agency from liability. Because of this, they may not be enthusiastic about permitting greywater. In states that have laws that do not require permits under certain circumstance, like Arizona, New Mexico, and Texas, and now California, the officials may not be aware of the code. It can be helpful to share with them other examples. You can download the codes from Arizona and New Mexico on the About greywater page. On the City of Santa Barbara's website there is a schematic people can use. Interviews with the health department in Arizona reveal that there have been no complaints from neighbors related to greywater since 2001, the year the code changed.
In states without codes, or with restrictive codes, the vast majority of people who want to reuse their greywater do so with out a permit. The alternative is to explore an "Alternative methods and materials" permit, which is intended to allow for new or alternative systems not covered under the current code.
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.
Can I use the water from a dishwasher?
Dishwashers are not a good sources of greywater because the detergents for dishwashers are high in salt. Salt will destroy the structure of your soil over time. If you are able to find a dishwashing detergent that does not have salt or boron in it, then the greywater can be reused. If you have to use the dishwater greywater, send it to a dedicated portion of the yard and plant with salt tolerant plants. Dishwashers are not included in most greywater codes (Montana is an exception), since the kitchen sink is excluded entirely.
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.
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. 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.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)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.
Conserving elevation. Keep the greywater pipes as high as possible so they can exit the house over the foundation.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.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 2A 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!
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.)
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.
How to 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.
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 is a product that can transform water inside the septic tank into irrigation quality water, which can be sent through a drip irrigation system