What laundry detergent should I use for greywater applications?


When your laundry water is going to the soil instead of to the sewer (or a septic tank) you need to make sure that detergent is friendly to soil life. Your big brand detergents are a no-go. And even the various eco-detergents, even ones marked “biodegradable”, are not appropriate for the soil because they are essentially salt-based. They play well with aquatic life, bless them, and they’re a great alternative to more toxic detergents if your laundry water is going to the sewer, but they aren’t good for soil microorganisms. Surely you’ve heard that salting the land is a bad idea? You don’t want to salt your garden. Those salts will build up in the soil and can cause salt burn on tree leaves. (This appears as leaves with browning tips, as if they’ve been sunburned.)

It’s worth adding that the drier your climate, the saltier the soil, because there is not enough rain to help percolate it away–so if you live in a dry climate it’s even more important to be careful with salts.

Homemade detergents–the ones based on soap and washing soda–are also not an option, again because of their salt content.

This leaves you with two options, at least as far as we know. If you know another detergent which is specifically formulated for greywater use, please let us know.

1)  The first is a laundry detergent called Oasis Biocompatible, sold by Bio Pac. This is what we use. It’s a basic, colorless, odorless, super concentrated liquid detergent, specifically formulated for greywater use.  It works very well, but doesn’t have the bells and whistles of “whiteners” and “brighteners” found in grocery store brands. To me, this is a plus.  It is not found on supermarket shelves. I have seen it in some health food stores, but we order it online. This is not too bad of a deal because it is concentrated, so a gallon bottle lasts a long time.

2)  The second option is soap nuts. Soap nuts are the dried fruit of the soap nut tree–they look a little like a cross between a date and a hazelnut. They are full of natural saponins (soaping agents) which are released in the wash. These saponins have been tested and don’t harm soil life.

You just drop 3 or 4 of the nuts into a little muslin bag (which comes in the box), and throw that bag in the wash with your clothes. They activate better in hot water, so some people will opt to soak the bag in a cup of hot water first–like making tea–and then dump the water and the bag into the wash.  Other people stew the nuts in water and make soap nut tea, which can then be used like liquid soap, for both hand washing and laundry. There’s lots of info online about soap nuts if you poke around a bit.

I just remembered that I posted here back in 2010, asking for feedback on the nuts, and got lots of it. So you might want to check that out.

If you’ve never heard of soap nuts, the whole idea might seem strange. But remember, all soap really does is help water work better, and they release soap. The real washing power is the agitating water in your machine.

Incidentally, both Oasis and soap nuts are fine for HE washing machines.

ADDENDUM: Option #3:  Thanks to commenters Kay and Matt, I’m going to add a 3rd product to this list: Ecos  Laundry Detergent. It claims to be greywater safe, I checked the ingredients and saw no salts, and Matt says he’s used it for a year successfully. Sounds good to me! Also in the plus category, this Ecos seems easier to find in stores than Oasis. Addendum to the addendum: Ecos contains sodium coco sulfate which some folks do not consider biocompatible.


Pure castile soap, like liquid Dr. Bronners, is okay for the soil, but it doesn’t really work as a laundry detergent. You can use it as such for the occasional load, but you will find your clothes turning grey with extended use. Sometimes, however, if I’m dealing with a musty or stinky load of laundry, I’ll put a squirt of scented Dr. Bronners into my machine along with my Oasis or soap nuts, since Oasis is odorless, and soap nuts have a bit of an organic scent (which doesn’t linger on the clothes).

Laundry additives:

You also need to be careful with laundry additives when your laundry water is going to the garden. No bleach, obviously. Bleach alternatives, like OxyClean, are also suspect because they are often based on sodium percarbonate. Check the ingredients and scan for the word sodium. If you see it, it’s best to avoid the product. For this same reason, no baking soda (sodium bicarbonate) either, or washing soda (a sodium salt of carbonic acid).

Vinegar is okay, lemon juice is okay, and I don’t see how small amounts of hydrogen peroxide would hurt anything, though I’d want to do more research if I made it a regular part of my laundry rituals.  I’m suspicious of the various specialty stain removers. If you’re just squirting one spot on a shirt, obviously it will be greatly diluted in the wash water, but really, who knows what is in these stain formulas? When you use greywater you really learn the meaning of “closed loop” — you have to live with what you put out there. So, the decision is yours in the end.

So how do you use your “nuclear option” type laundry additives? Read on, dearies.

The Importance of a Three Way Valve:

It is well worth the time to install a diverter valve by your machine which allows you to choose whether your wash water will go to the sewer or the garden. If you have one of these, you can do loads with bleach or what-have-you and send that water to the sewage treatment plant.

Also, if you are washing diapers, this valve is an absolute necessity. All diaper wash water should go to the sewer. Soil is a great cleanser, but you don’t want to push your luck by depositing fecal matter around your garden.

(Addendum here, too: I spoke a little too absolutely above. It is possible to reuse that water, but you need to do so very carefully.  Diaper water is blackwater, not greywater, and needs to be handled in specific ways  Perhaps we’ll do a separate post on that later.)

Finally, during periods of heavy rain you may just prefer not to send any more water to the garden, and this allows you to make that choice.

A few words about other greywater applications:

If you’re using greywater from your shower, most soaps and shampoos are okay. Though again, I’d remember the closed loop principle and try to use soaps and shampoo from the more natural end of the spectrum.  Again, good ol’ Dr. Bronners, soap or liquid form, is something I’d feel good about sending out to the landscape.

Bio Pac also makes a concentrated soap which is a sister to the Oasis Detergent called Oasis Dishwash/All Purpose Cleaner. This is an all purpose soap that you can even use in the shower. This would be a good product to use for more casual water recycling–so when you’re cleaning house, say, you can safely dump a bucket of dirty water outside and know that it won’t harm your garden.

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  1. Amazing information! I never thought of this before :) I am going to file this away to my very useful stuff folder and share with my farm friends.
    Thank you!

  2. Thank you for the info! Could you or your readers please chime in with what you use for dishes? Most of our dishes go into our super high-efficiency dishwasher, but I’d like a way to reroute the sink water when I’m washing pots and pans. Dr Bronners is fine for handwashing and mopping floors, but I need something with more oomph for my dirty pots.

  3. Hydrogen peroxide will have some bleaching effect (though it works wonders with blood). I’ve got a few pieces of clothing with lighter areas from using it. Definitely test or research before applying it straight.

  4. The BioPac site won’t let us order the laundry detergent directly from them. Instead it says “UPS has been destroying cases.” What the?

    • It can be a bit frustrating sometimes to find Oasis detergent. Sometimes Amazon has it and sometimes they don’t (right now they don’t but they had it late last year when we last ordered it). I’ve always managed to find someone selling it online.

    • ??? That is very strange! But we’ve always managed to get it. A slight correction to Mr. H. — we bought our last bottle through Amazon only two weeks ago, but not via Amazon itself but a retailer called Nutricity. I suspect it will come back in stock soon.

  5. Well, I still love my soap nuts. I keep meaning to try making soap from conkers (Horse Chestnut, Aesculus hippocastanum, naturalised in the UK) but as well as being hard work, I have read that it may discolour the clothes, so it’s not very high up my to do list. One of my Rainbow Guides made soap from some after we collected lots at a meeting, but I’m not sure her dad will be doing it again this Autumn after grating dozens of conkers to do it!

    Yes, the soap nuts are imported (the usual criticism), but they’re dry, so they can be shipped rather than flown; they’re fair trade and I bet the miles clock up on all the ingredients in even eco-products anyway.
    I use them in the dishwasher too now and just compost them when they’re soggy.

  6. We’ve used ecos successfully for more than a year in our laundry to graywater system. As another commenter posted, it states that it’s graywater safe and it’s available at our local whole foods.

    We actually push the cloth diaper graywater out to the landscape. It’s for non-edibles, discharges to mulch basins below the surface, and is not in a place that gets foot traffic – so why waste the nutrients?

    • Good point about the diaper water, Matt. I spoke too absolutely when I said not to use it, probably because subconsciously I didn’t want to get into explaining the ins and outs of it all. It can be used, yes, if you’re very careful, and have done your research. It sounds like you’re dealing with that black water safely by keeping it underground in deep mulch basins.

      I wouldn’t want to encourage someone new to greywater using diaper blackwater inappropriately in their enthusiasm. For instance, we know of someone who hooked their blackwater to sprinklers. Sprinklers!!!

      My new slogan: “We must respect the poo.”

  7. @Kay and @Matt

    Thanks for the tips about Ecos. I checked the ingredients and yep, no salts, so I’m going to amend the post to include it.

  8. My interest stems from treating water and sending effluent to field, or wetland areas and the effect SAR presents, as such your article applies. I would like to caution statements made about what is sent to treatment as that invariably ends up in nature and we can only treat to the influent quality. Sodiums, chlorine and such are harmful to the biological process, get the picture. Stop Sodium and allow some phosphates, that we can manage globally much better

  9. Thank you for this awesome post! I’m looking into Ecos, my local co-op sells it which is great. However, in the ingredients “Sodium Coco-Sulfate (coconut-based surfactant)” is listed. Is this not a bad type of salt? Thank you!

    • Caitlin–thanks for spotting this. I’ve updated to post to note that some folks do not consider sodium coco-sulfate to be a biocompatible ingredient.

  10. I just recently discovered a website on ‘garbage enzymes’ made by using 10 parts water, and 1 part brown sugar and 3 parts vegetable/fruit waste, fermented 3 months. Sounds weird, but here is the link to this. I am excited about it. I just had my first batch, added a small amount to the toilet to clean (excellent), used it to clean drain, and added to hand soap as recommended. It is also useful for insecticide, garden fertilizer, etc. It seems it might be something that would also be useful for those who are doing the graywater systems.


    They also believe this helps clean up the environment. A wonderful idea, and certainy, another great reuse for our garbage. Once fermented, you can still throw the strained organic solids into the compost heap or your garden directly,

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