Green Your Garden with Greywater

September 26, 2016  |  Blog


Author: Ted Labbe. Long long time depaver, current board member and backer of all things greywater.

Portlanders love their gardens. But have you ever stopped to consider how much water your garden consumes? Our abundant fall-winter-spring rainfall comes out of sync with the summer garden irrigation season. Peak water use by City of Portland residential customers is in July through September when water use increases by 30-50% to feed those thirsty veggies, fruit trees/shrubs, and lawns. Even a small bed of veggies and a few fruit trees can consume 5,000 gallons of water over one irrigation season. That is a lot of pristine Bull Run drinking water!

Peak water use by City of Portland residential customers is in July through September when water use increases by 30-50%


Portland’s Water Use vs Rainfall

That’s one reason why Depave promotes naturescaping, integrated with thoughtful rainwater harvesting techniques (like rain gardens), at our project sites. Native plants are adapted to our climate and can thrive without supplemental irrigation. Using mulch and soil amendments we can boost water storage in our soils, which is the cheapest and most effective place to store all that rain – for the benefit of our plants and everything else downstream.

But many of us love our home-grown veggies and fruit and we know they need summer irrigation to thrive. Portlanders with green thumbs often jump to rainwater catchment and storage in tanks as the fix for their garden irrigation needs. But it can be tough to find space to store all the water you need for a whole season of garden irrigation. Large tanks also can be cost-prohibitive and unsightly.


Shut off valve

What if you could get a second use from the water draining your shower, sink, and clothes washer and use it in your yard? You can. It is called GREYWATER. And since 2011 it has been legal in Oregon to use your own greywater, if you follow some simple procedures.

Used wisely, greywater is safe for you and your plants. During the summer you redirect greywater to your yard. In the wet season you shut off your system and send all wastewater to the sewer.

But won’t the soapy wastewater hurt my plants? Nope. You must switch your clothes washer and dish soaps over to plant-friendly ones (those without salts, boron, or bleach), but there are a variety of good ones to choose from. Regular body soaps are fine. The only no-no is dishwasher effluent, since there are no boron/salt-free soap options. The other stuff in your wastewater is actually beneficial for your plants.

You can’t use the water from your toilet (that is “blackwater”), or store your greywater for more than 24 hours – it will stink! All greywater systems need some basic periodic maintenance. So it isn’t right for everyone (and every site). You need to consider the site, the users, and plant needs.

Greywater isn’t a panacea, but it is a compelling part of a well-rounded water conservation and (re)use strategy, that includes water-efficient appliances, drip irrigation, rainwater catchment, naturescaping, human behavior changes, and more.

Greywater is being designed into new construction in drought-stricken regions across the world. But there are affordable DIY retrofit systems that you can implement at home with a minimal investment of time and resources. One of the simplest is the laundry-to-landscape (L2L) system and uses the pump in your clothes washer to deliver wastewater to your plants. A branched drain system uses just gravity and pipes (no pumps or other moving parts) to water your thirsty fruit trees. There are also more elaborate designs with pumps and filters that cost more and can require more maintenance.

These low-tech systems are not good for lawn or low-growing food plants that could potentially contact the ground (ex. strawberries). But they are perfect for fruit trees, berry bushes, upright veggies (tomatoes, broccoli), and more.

The first step is to assess your home water use, and implement water conservation measures like low-flow faucets and showerheads. (Plus maybe replace that old water-hog of a clothes washer?) Then design your system to match your plant’s water needs with the knowledge of your greywater flow and site constraints. There are lots of tips and tricks to learn about and some of the best greywater resources are listed below.

After you assess your water use and yard, implement water conservation measures, and design your greywater system, you need to get a permit from Oregon DEQ here. For any home-interior plumbing work you may also need a permit from your City building department. Then you are ready to build!

At this stage you may be thinking: “Great! Who can I hire to help me design and build my system?” Unfortunately, right now there are not many seasoned residential greywater system installers in Oregon and even with the recent drought there have been few systems permitted. This is one reason why Depave is helping host informational and how-to workshops: to build a local community of greywater practitioners, proponents, and resources for those interested.

Depave is helping host informational and how-to workshops: to build a local community of greywater practitioners


Laura Allen teaches Portlanders about greywater in Aug 2016.

We think greywater is perfect for Portlanders with green thumbs. It is good for our pocket books, our plants, and the planet. It can help close the loop on our wasteful residential water use patterns. Folks that implement greywater systems begin to carefully scrutinize their soaps and are less prone to simply dump random stuff down their drain.


Portlanders dig in during the Aug 2016 hands-on greywater workshop.




Depave is so excited about the possibilities for greywater in Portland (and the synergism with our work-to-date) that we hosted two workshops in August 2016 introducing greywater residential reuse and the DIY retrofit systems mentioned above. The workshops were taught by Laura Allen, author of The Water-Wise Home and a co-founder of Greywater Action). To host these workshops we partnered with Greywater Action, Recode, Oregon Tradeswomen, and East Multnomah SWCD. The workshops were a great success and we are contemplating more in 2017. Tell us about your interest in follow up greywater workshops here.



Greywater Action’s website is a great place to start learning about greywater and DIY home systems. A co-founder of Greywater Action, Laura Allen, has a great book with more details, tips and tricks if you want to learn more: The Water Wise Home is available from the Multnomah Co Library or Powell’s Books. This is our favorite book on greywater – it is the easiest to understand and use.

Get local (Portland metro region) info on water saving tips, learn about rebates, and find out where your water comes from through the Regional Water Providers Consortium.

Brad Lancaster’s comprehensive water harvesting website has lots of info, links, and photos on greywater systems here.

Art Ludwig, the creator of the original L2L and branched drain designs has a great website on greywater do’s and don’ts here. He also has a book: The New Create an Oasis with Greywater available from Multnomah Co Library and Powell’s Books.


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