Watermark H2O's Logo

Watermark H2O

Located in Santa Cruz serving all of California

Call us at (408) 690-7581
Watermark H2O's Logo

Watermark H2O

Located in Santa Cruz serving all of California

(408) 690-7581

About Greywater Reuse


Greywater is water from your bathroom sinks, showers, tubs, and washing machines. It is not water that has come into contact with feces, either from the toilet or from washing diapers.

Greywater may contain traces of dirt, food, grease, hair, and certain household cleaning products. While greywater may look “dirty,” it is a safe and even beneficial source of irrigation water in a yard. If released into rivers, lakes, or estuaries, the nutrients in greywater become pollutants, but to plants, they are valuable fertilizer. Aside from the obvious benefits of saving water (and money on your water bill), reusing your greywater keeps it out of the sewer or septic system, thereby reducing the chance that it will pollute local water bodies. Reusing greywater for irrigation reconnects urban residents and our backyard gardens to the natural water cycle.

The easiest way to use greywater is to pipe it directly outside and use it to water ornamental plants or fruit trees. Greywater can be used directly on vegetables as long as it doesn't touch edible parts of the plants. In any greywater system, it is essential to put nothing toxic down the drain--no bleach, no dye, no bath salts, no cleanser, no shampoo with unpronounceable ingredients, and no products containing boron, which is toxic to plants. It is crucial to use all-natural, biodegradable soaps whose ingredients do not harm plants. Most powdered detergent, and some liquid detergent is sodium based, but sodium can keep seeds from sprouting and destroy the structure of clay soils. Chose salt-free liquid soaps. While you're at it, watch out for your own health: "natural" body products often contain substances toxic to humans, including parabens, stearalkonium chloride, phenoxyethanol, polyethelene glycol (PEG), and synthetic fragrances. (To learn more about what’s in your products, go to the Cosmetic Database and see how they rate for toxicity). http://www.safecosmetics.org/

Our philosophy

We believe that for residential greywater systems simple designs are best. With simple systems you are not able to send greywater into an existing drip irrigation system, but must shape your landscape to allow water to infiltrate into the soil. We recommend simple, low-tech systems that use gravity whenever possible, instead of pumps. We prefer irrigation systems that are designed to avoid clogging, rather than relying on filters and drip irrigation.

We promote greywater reuse as a way to increase the productivity of sustainable backyard ecosystems that produce food, clean water, and shelter wildlife. Such systems recover valuable "waste" products--greywater, household compost, and humanure and reconnect their human inhabitants to ecological cycles. By modeling "appropriate technologies" for food production, water, and sanitation in the industrialized world, we hope to replace the cultural misconception of "wastewater" with the possibility of a life-generating water culture.

We believe more complex systems are best suited for multi-family, commercial, and industrial scale systems. These systems can treat and reuse large volumes of water, and play a role in water conservation in dense urban housing developments, food processing and manufacturing facilities, schools, universities, and public buildings. Because complex systems rely on pumps and filtration systems, they are often designed by an engineer, are expensive to install and may require regular maintenance. If you are interested in learning more about more complicated residential or commercial systems please contact us at www.watermarkh2o.com

Basic Greywater Guidelines

Greywater is different from fresh water and requires different guidelines for it to be reused.

  1. Don’t store greywater (more than 24 hours). If you store greywater the nutrients in it will start to break down, creating bad odors.
  2. Minimize contact with greywater. Greywater could potentially contain a pathogen if an infected person's feces got into the water, so your system should be designed for the water to soak into the ground and not be available for people or animals to drink.
  3. Infiltrate greywater into the ground, don’t allow it to pool up or run off (knowing how well water drains into your soil (or the soil percolation rate of your soil) will help with proper design. Pooling greywater can provide mosquito breeding grounds, as well as a place for human contact with greywater.
  4. Keep your system as simple as possible, avoid pumps, and avoid filters that need upkeep. Simple systems last longer, require less maintenance, require less energy and cost less money.
  5. Install a 3-way valve for easy switching between the greywater system and the sewer/septic.
  6. Match the amount of greywater your plants will receive with their irrigation needs.

Types of simple systems

From the Washing Machine

Washing machines are typically the easiest source of greywater to reuse because greywater can be diverted without cutting into existing plumbing. Each machine has an internal pump that automatically pumps out the water. You can use that to your advantage to pump the greywater directly to your plants

Laundry to Landscape(aka Tank less laundry systems):

If you're looking for system that gives you flexibility in what plants you're able irrigate and takes very little maintenance, we recommend the laundry to landscape system.

In this system the hose leaving the washing machine is attached to a valve that allows for easy switching between the greywater system and the sewer. The greywater goes to 1" irrigation line with outlets sending water to specific plants. This system is low cost, easy to install, and gives huge flexibility for irrigation. In most situations this is the number one place to start when choosing a greywater system!

From the Shower:

Showers are a great source of greywater- they usually produce a lot of relatively clean water. To have a simple, effective shower system you will want a gravity-based system (no pump). If your yard is located uphill from the house, then you'll need to have a pumped system.

Branched Drain:


Greywater in this system flows through standard (1 1/2" size) drainage pipe, by gravity, always sloping downward at 2% slope, or 1/4 inch drop for every foot traveled horizontally, and the water is divided up into smaller and smaller quantities using a plumbing fitting that splits the flow. The final outlet of each branch flows into a mulched basin, usually to irrigate the root zone of trees or other large perennials. Branched drain systems are time consuming to install, but once finished require very little maintenance and work well for the long term.

From the Sinks:

Kitchen sinks are the source of a fair amount of water, usually very high in organic matter (food, grease, etc.). Kitchen sinks are not allowed under many greywater codes, but are allowed in some states, like Montana. This water will clog many kinds of systems. To avoid clogging, we recommend branched drains to large mulch basins. Much less water passes through bathroom sinks. If combined with the shower water it will fall under the shower system, if used alone, it can be drained to a single large plant, or have the flow split to irrigate two or three plants.

Constructed Wetlands:

constructed wetland

Wetland planter ecologically disposes greywater from an office with no sewer hookup. If you produce more greywater than you need for irrigation, a constructed wetland can be incorporated into your system to "ecologically dispose" of some of the greywater. Wetlands absorb nutrients and filter particles from greywater, enabling it to be stored or sent through a properly designed drip irrigation system (a sand filter and pump will also be needed). Greywater is also a good source of irrigation for beautiful, water loving wetland plants. If you live near a natural waterway, a wetland can protect the creek from nutrient pollution that untreated greywater would provide. If you live in an arid climate, or are trying to reduce your fresh water use, we don't recommend incorporating wetlands into greywater systems as they use up a lot of the water which could otherwise be used for irrigation.

Pumped Systems:

If you can't use gravity to transport the greywater (your yard is sloped uphill, or it's flat and the plants are far away) you will need a "drum with effluent pump" system. The water flows into a large plastic drum that is either buried or located at ground level. In the drum a pump pushes the water out through irrigation lines (no emitters) to the landscape. You can also use one of our Water Wise Aqua2use Greaywater diversion Device plug & play system if you have an elevation issue that are relatively easy to install in most cases and is reasonably priced. These systems have a pump head of up to 25’.

pumped system

Indoor Greywater use

In most residential situations it is much simpler and more economical to utilize greywater outside, and not create a system that treats the water for indoor use. The exceptions are in houses that have high water use and minimal outdoor irrigation, and for larger buildings like apartments.

There are also very simple ways to reuse greywater inside that are not a "greywater system". Buckets can catch greywater and clear water, the water wasted while warming up a shower. These buckets can be used to "bucket flush" a toilet, or carried outside. There are also simple designs like Sink Positive, and more complicated systems like the Brac system. Earthships have an interesting system that reuse greywater inside with greenhouse wetlands.

Plants and Greywater

palnts greywater

Kiwi fruit irrigated with greywater. Low tech, simple greywater systems are best suited to specific, large plants. Use them 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. (Like a lawn or flower bed) Read more about recommended plants to water on the following Page: Choosing plants and irrigating with greywater

Choosing plants and irrigating with greywater

Great plants for greywater


Apple tree irrigated with greywater. Whatever your water source, grow plants that produce food, provide habitat to wildlife, or create other beneficial uses like mulch, fertilizer, fuel, or building materials!

Fruit trees
Most fruit trees thrive on greywater, and there are many delicious options! They can tolerate frequent watering and once established they can go long periods with no water.

  1. Choosing a fruit tree: To start, use root stocks that are resistant to local diseases (ask at your local nursery or Cooperative Extension) and plant trees that are known to grow well in your area. Your tree will also do better if it has good soil; adding compost may be helpful.
  2. Drainage: Next, consider the drainage of your site. If drainage is poor, you will need to plant the tree on a mound and water it less to prevent diseases like crown rot. When planting trees ensure that the crown of the tree is above the mulch basin to prevent crown rot.
  3. Salt: Fruit trees are generally salt sensitive and should not be irrigated with water from powdered detergents or other products containing salts. If your greywater source contains lots of salt (dishwasher detergent, for example, is high in salt), add salt-tolerant plants to your landscape, or irrigate frequently with rainwater to flush salts from the soil. Plants that thrive on recycled or reclaimed water (highly treated wastewater) are good choices for high-salt greywater.

Other plants
Other perennials that thrive on greywater include edible shrubs and vines such as raspberries, thimbleberries, blackberries and their relatives, currants, gooseberries, filberts, rhubarb, elderberry, passion fruit, kiwi, hops, and grapes. Blueberries love acidic soil so you'd have to be careful if irrigating them with greywater, and use pH neutral soaps or acidic mulch.

Where to irrigate trees


Greywater discharged in drip line of tree. A trees' feeder roots extend well past the drip line (the outer edge of the branches). If the drip line is 10' from the trunk (for example), dig a mulch basin 15' from the trunk. (Do the best you can if a foundation or sidewalk is in the way). Plan the system so you can extend the irrigation zone outwards every few years as the tree grows.

Quantity of water

You can either send a lot of greywater to trees that love water, or spread it out more and water trees that need less. A mature tree can absorb huge amounts of water, but it can also live just fine with little extra watering. For example, a medium sized fruit tree (10 ft. canopy diameter) in coastal California is recommended to receive about 12 gallons per day, or 84 gallons a week, and the same tree inland needs about 20 gallons/day, or 140 gallons a week for optimum production. We've observed several similar sized trees in coastal CA that receive a fraction of that and fruit prolifically! Many established fruit trees are never watered in backyards and survive just fine; with just a little greywater they'll begin to fruit more.

As you can see, irrigating with greywater is not an exact science. We usually split up the flow from one fixture (like a shower) to irrigate 4-6 trees, depending on the amount of water, the size of the trees, and the drainage of the site.

A simple diverter valve allows you to irrigate 2 zones of fruit trees. Some fruit trees prefer less frequent, deep watering’s, allowing the soil to dry between irrigating. Incorporating different "zones" into the greywater system allows for this. You can alternate between groups of trees every other week. Some trees, however, are fine and happy getting watered all the time. This partly depends on the drainage of your site. A simple home 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.

How to irrigate with greywater

Greywater can either be discharged on the surface of the ground, over mulch, or it can be discharged below the ground. If greywater is discharged directly onto the bare ground it can clog the soil by filling the small air gaps in its structure. It will drain slowly, often causing pooling (something to avoid). Mulch prevents this from happening. Mulch can be any type of wood chips, straw, or bark. The new code in California requires the point of discharge to be under 2" of mulch or other barrier.


  • Discharge onto mulch.
  • Have an air space between the pipe and the ground. This will prevent roots from growing back into the greywater pipe and clogging it.

Homemade mulch shield on the left.

mulch mulch

Greywater from a shower discharges into a valve box a few inches above the mulch level on the right.

Greywater Policy

Greywater policies differ state to state. The best policy is form 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 its code, making it much easier for people to build simple, low cost systems legally.