Working with greywater sources

Greywater is defined as water that has already been used in a household water supply that does not come from the toilet. (Toilet water is blackwater) Water from sinks, showers and washing machines qualify as greywater. It is too dirty for people and pets to drink but not too dirty for plants to drink as the plants are able to filter out the nasty from the water and just use the good stuff. A properly designed greywater system in essence, is a biological filter for your home’s wastewater.

Creating a greywater distribution system can be very simple. A bucket under a handwashing sink catches the draining water, at the end of the day you take the bucket out and dump the water onto a tree. That’s it! The concept relies entirely upon redirecting the greywater that would have otherwise ended up in a wastewater system onto a secondary source such as a shade tree, that can then add further value to a home.

But it does not stop there, the concept can be refined and elaborated upon to create a system that works time and time again without any additional user input and requires minimal maintenance. These are the systems that I design and install and it just takes a little more information from the basics to get there.

Construction of wetland for cleaning and distributing high amounts of laundry water
Construction of wetland for cleaning and distributing high amounts of laundry water

Important Safety Considerations

First off, greywater is only one step away from blackwater, ie. poo poo water, so we need to address and understand some health and saftey concerns and state regulations before beginning the design. Texas is not a highly regulated state but there are in fact, state regulations regarding the distribution of greywater, mostly regarding spetic tank sizing. That should tell you something right there about the importance of a correct design. The State of New Mexico also has some additional regulations that are worth reading as they are more specific about the actual practices of using the greywater.

An interesting point to note about Texas and New Mexico regulations is that a common source of greywater, the kitchen sink, is NOT allowed in greywater reuse systems. Think for a minute about everything that might end up in a kitchen sink like animal blood, grease and larger pieces of vegetables. What if you just did an oil change on your car and you need to wash up? Having the kitchen sink drain to the septic helps keep potentially toxic water out of the greywater system and out of the biological filter that you are building in your greywater treatment plan.

Pro Tip

If you are happy to DIY then I highly recommend to buy this book by Art Ludwig, there is no better resource with regards to greywater technology. Create an Oasis with Greywater
Most of my designs are based entirely upon or modified slightly from the concepts in this book and Art’s decades of experience in greywater systems. For immediate satisfaction you can browse the site to dig deeper into the information.

First things to consider

The following are expectation checks for Terlingua greywater systems just to get you started before you start designing.

  • Designs are best before construction begins. A newly conceived outdoor shower or washroom is an excellent candidate for greywater reuse. An existing fully plumbed in-slab system that drains to septic is not.
  • If you leave your homestead for several months at a time, create a backup plan for the plants that depend on your greywater system. This could mean a neighbor using your clothes washer or a system designed only for annuals.
  • Our soil is salty and alkaline and greywater irrigation increases the salinity by the addition of pee, sweat and soaps (yes you do pee in the shower and almost all “natural” cleaners contain sodium laurel sulfate) Soil quality will degrade over time without periodic flushing of salts or replacement of all soil, only conceivable in a containerized bed.
  • Grewater is best if it infiltrates the soil immediately, holding onto greywater by draining into a holding tank or letting it pool at the surface is not good practice.

Should you grow food with greywater?

The chance of contamination from greywater goes up the less water is filtered and the closer it comes to your mouth. The best practice is to leave greywater for growing shade, not food. You should balace your risk tolerance on a scale of 1-10.
1 (least risk) = using greywater for sub surface watering of landscape plants
10 (most risk) = directly pouring greywater on lettuce plants and not washing the leaves before fixing a salad.
Somewhere in between is using greywater for an edible fruit tree such as a pomegranate– you must be the judge and I will make no claim that I told you either or.

Garlic grown with pure rainwater only


Data compiled by the EPA indicates that, as a national average, landscape irrigation is by far the largest single use of water at both residential and commercial sites, using 59% and 35% of water, respectively (EPA, 2013) In hot climates, outdoor use ranges from 59%-67% compared to 22-38% in cooler climates (AWWA, 1999). There is no doubt that water is our most precious resource so if we can use rainwater and use it twice then we can achieve a much greater efficiency in our landscapes. Using greywater to water roots, which then grows to provide shade to our living areas just makes perfect sense.

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