Greywater: What Is It And How We Use It
by 2021 apprentice Matthew Raybon
One of our compost toilets where the sink greywater flows onto our orchards
What is Greywater
Greywater is the “waste” water that comes from all household plumbing that is not a toilet. This includes, the shower, bathtub, sinks, and hoses. In most of the contemporary world, greywater is seen as wastewater and is combined with sewage to be chemically treated and dumped into the nearest waterway. In the average household, non-toilet uses make up around 2/3 of water used. This adds up to about 30-50 gallons per person each day. Greywater’s cousin, blackwater, which is the water used by the toilet, makes up the rest of the water used in the typical household. This amounts to around 15-30 gallons of water per person each day (Van Der Ryn, 81). Read about our compost toilets or our biodigester and how these are a more sustainable solution for toilets.
All of our shower grey water is directed to orchard spaces
Woah! That is a whole lot of water. Now, imagine a world where that thing that we currently refer to as “waste” is highly revered as a RESOURCE! A precious thing worthy of a second life where it can aid in enriching the soil and fueling our journey towards a more holistic life. As it turns out, this is more than possible for the average household to pursue and achieve with a little bit of research, design, implementation and maintenance. Using our greywater as a resource hits many principles in permaculture.
Designing your greywater system
To many people the idea of using something that we typically think of as waste to help grow food or water our plants seems unsafe. While greywater is unsafe to drink, if handled and used properly, it is perfectly safe for certain applications. In order to begin designing the appropriate greywater system its necessary to ask a few simple questions:
What is the volume of greywater being produced?
What is the source of the greywater? Is it a kitchen sink or a washing machine?
What is the intended application for the greywater? Are you irrigating an orchard or a vegetable garden?
Once we have answered these questions we can move on to designing and testing a system. At Rancho Mastatal we use a series of very simple low maintenance systems to distribute our greywater as irrigation for our ourchard spaces and ornamental beds. Most of our greywater is coming from our four kitchen sinks and two washing machines. As the water leaves the sink or appliance, it enters into a simple system of surface level PVC piping which utilizes the natural slope in the landscape to direct the greywater to various orchard spaces and ornamental beds. Once the water arrives at the intended zone it is important to distribute the water within the field or garden in a way that does not contribute to erosion or oversaturate one particular plant or tree. Think of a greywater system as a gravity fed, all natural fertilizer delivery system. We want it to feed our trees, but in moderation. In most cases this can be easily accomplished with a combination of branch drains, swales, and detention ponds which will slow spread and sink the water into the different areas.
Branch Drain System
Since our kitchen is particularly active (serving anywhere between 14-30+ people at a time) we use a simple branch drain which splits the grey water into three different pipes. Then these pipes each drain into separate swales. These swales allow the greywater to infiltrate the soil, feeding an orchard space full of bananas, breadfruit trees, and chaya.
Banana Circle
In another application, three less active sinks combine with the rainwater runoff from the roof of the food smithy and main house. This water collects in two small nearby ponds. Around the ponds, in the berm, we have planted a few varietals of banana as well as some Katuk for easy salad access. The greywater that collects in those ponds is diluted with the rainwater from the roof. As it slows and sinks into the earth it helps break down the mulch creating rich and active soil. These are often refered to as banana circles, but you can plant anything on the berms besides bananas.
Things to Consider
When designing your own system its important to consider the different sources of greywater. Kitchen sinks typically contribute the majority of the organic material of your greywater production. In nearly all situations this includes some volume of oils or grease. It’s important for the maintenance of your system to have some sort of grease trap installed in order to prevent the plumbing from clogging. Here at Rancho, we have a greywater and grease trap maintenance check scheduled on our calendar every month. This ensures that the system is maintained.
When utilizing greywater from your washing machine, it is important to consider what sort of soap or detergent is being used and what the environment is that the water will be entering into. Fortunate for us in the tropics, our ecosystem is extremely resilient. This makes it able to mitigate many of the chemicals that go into typical detergents. That said, it is best to avoid boron based detergents and detergents that tout their “softening” abilities.
When it comes to managing the human or synthetic inputs going into the greywater, the strategy that always wins is twofold. First- be conscious of the quantities that are being used. Second- be sure to dilute the greywater with fresh water! In our case at Rancho Mastatal, we experience high levels of rainfall throughout the larger part of the year. Thankfully, this heavily assists in diluting of our greywater inputs.
Applying Greywater
While greywater has the potential to be an incredible resource, it is important to manage and use it properly. As a general rule, its best when directly applied to the soil particularly in orchard type spaces. Here is a brief list of guidelines for applying greywater in food producing spaces:
Guidelines for applying greywater in the garden:
Apply directly to soil; avoid overhead sprinkling
Deliver greywater to relatively flat areas or an earthwork designed to slow and spread the greywater
Use branch drains and swales to disperse the greywater
Apply mulch and compost to areas receiving greywater to facilitate decomposition (stack functions)
Greywater is typically alkaline, so avoid using it on acid loving plants
Mix freshwater in with greywater irrigation - Dillution is key!
When selecting soaps and cleaning agents be conscious of what those things are made of
Try to avoid boron based detergents and detergents that tout their softening powers
Be conscious about your usage of chemical inputs
Dilution is key! Through the use of a mixture of freshwater (rainwater or otherwise) and grey water, the rich micro biome in your garden or orchards soil will be able to effectively process and integrate the greywater inputs.
Want to Learn More
Join us for our annual Permaculture Design Course to get inspired and hands on education in subjects such as greywater, natural building, agroforestry, and general good practices to designing a more sustainable home and environment.
Swale digging: Water management on the farm is key. Many hands make for much lighter work!