Water your Trees with Greywater

Ludwig’s Laundry to Landscape plans.

Root Simple reader MJ pointed out that I neglected to mention greywater as a way to deal with our drought challenged trees here in California. So, on this greywater Monday, I thought I’d round up some previous posts and links on the subject.

Laundry to Landscape
International greywater guru Art Ludwig has a set of free plans on his website Oasis Designs for a laundry to landscape system. I’ve built this system at our house and at a neighbors’ and can attest to its ease of construction and functionality. Make sure you read through Ludwig’s directions in their entirety or else you’ll blow out your machine’s water pump. And note that some California cities such as Pasadena have classes and rebates for greyater parts.

The Confusing World of Detergents
The combination of a dry climate and alkaline soils means that we have to be very careful about the sorts of detergents we use with greywater. Regular soaps and detergents will raise the pH of your soil. Your trees will look great for a few years and then suddenly die. Unfortunately, finding a soil-friendly detergent or soap is more complex than it should be. You can’t trust manufacturer’s claims of greywater compatibility. Here’s what Kelly concluded in a 2015 post:

As of today, we are still only able back three products without reservation for use in greywater:

• Oasis Liquid Laundry Detergent
• Bio-Pac Laundry Detergent
• soap nuts

ETA 8/14: Also, it looks like Fit Organic Laundry Detergent is safe as well. Thanks, Judy!

Sorry folks, I know that’s not a lot in terms of choice.

The following eco-friendly detergents are often listed as greywater compatible, but we have reservations about them. We recommend you research these products more on your own, and consider your own greywater system as well as the specific plants and soil you are irrigating before deciding whether these should be used or not.

Ecos: Contains sodium coco sulfate

Vaska: Has a D+ rating on the Environmental Working Group’s product safety database.

Lifetree: Has a pH level of 7

Dr. Bronner’s liquid soap: Fine for greywater use in general, but it simply is not a laundry detergent–it’s castile soap. You can wash your clothes with it, but the results won’t be spectacular.

The bottom line is that we only trust the detergents and soaps that Ludwig himself designed: Oasis Biocompatible Laundry Detergent and Dishwash soap.

Here are Brad Landcaster’s thoughts on soaps and detergents. Let me also note the utility of Landcaster’s books and website when it comes to all things water conservation related, especially how to grade and configure tree plantings to optimize rainwater irrigation.

One last and rarely mentioned issue, is if “greywater” should be one word or two or, in the neologistic spirit of “apisoir,” perhaps we need to invent a sexier word for reusing our water. Greenwater? Freewater? Leave a comment!

Leave a comment


  1. Are you irrigating with your wash or rinse water? Normally, I only use the rinse water for irrigation, so was less concerned about salts. Wondering if I should be.

    • Both, and yes you should be concerned about salts if you live in a dry climate. Get the Oasis stuff and you won’t have to worry.

  2. I know nothing about greywater but have you checked out Charlie’s Soap? Their ingredients are SUPER simple (though I have no idea if its greywater safe).

    • I’m also curious about Charlie’s Soap. Both my husband and I have had skin reactions from even eco-friendly detergents in the past, but have used Charlie’s Soap for more than a decade.

    • It’s because 7 is on the high end of what cultivated plants like vegetables prefer. In our climate it would be more optimal to have lower pH water such as rain which, unfortunately, seems to be rare these days.

    • I hear you about the rain, we are also in the Southwest and having a dry winter!
      I’m mainly asking about the pH because 7 is about the lowest I’ve been able to find in a detergent. For example, I just looked up the MSDS for the Fit Organic detergent mentioned above, and it lists a pH of 11.8 … I work with textiles, so I know that alkaline conditions can be damaging to wool and silk (as well as not great for your plants). If you know the pH of the other recommended soaps, it would be great to compare.

  3. If you look on EWG’s site there are quite a few with a A rating. We have been using BioKleen cold water detergent for years and it works well. Our graywater system does not include laundry water though, we use the septic tank.

  4. Thanks for the detergent/dishwash soap suggestions! It is a real struggle finding truly biocompatible products, far too many tote being natural, or made from plant-based ingredients but that does not necessarily mean breaking down in an environment friendly way. I always end up spending half an hour looking at every label when I buy dish soap and still being dissatisfied. Our 15 year old saturn peach tree hasn’t looked so great these years, and I wonder if the decade of bathwater from my brother’s second story bathtub did it in, or if that is the life span of peach trees, I swear I read it somewhere… I’m tickled to get a mention, I’ve been a reader for many many years. 😉 Lastly, I want to mention that though graywater use is -awesome- and severely underutilized (I mean, what a great idea for a startup, it is a wonder there is no one making a successful business with graywater systems in L.A. – mark my words, I predicted slab marble ice cream would be a hit, then two years later the first coldstones started popping up), it faces an upward hill battle in a lot of places. Our friend’s retired parents in Colorado say it is illegal to use graywater in their area, so they had to install their system under the radar. Pretty ridiculus.. I am happy to see some public places use graywater to flush their toilets with, so perhaps we can slowly inch forward with progress.

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