Water Your Garden With Gray Laundry Water




About: By day I'm a mechanical engineer at a university laboratory. In my free time, I do my own projects.

For a long while I've wanted to be able to water our backyard ornamental garden with gray water. We already have a drip irrigation system and, while those are known for using water very efficiently, it still uses quite a lot of water. I researched gray water systems online and in books, but I didn't find any that would work similarly to a drip irrigation system by delivering the water to a large number of plants individually (actually, there are such systems, but they must be professionally installed and cost thousands of dollars).

Typical gray water garden systems deliver water to a few fruit trees or to large areas called "mulch basins" or they have water coming out of a hose that one can move around manually to different plants. What I wanted was a system that would take my gray water and distribute it to all of the places where the drip irrigation system goes. After almost six months of pondering this problem, last summer (2009), I hit upon a very simple solution that appears to work very well. I used it for a couple of months before our rainy season came, and then I switched the washing machine over to another water saving device, my laundry water recycler. Now the rainy season is coming to an end here in N. California, so I'll be reconnecting the irrigation system soon. Read on and you'll see how it works. I look forward to your comments and suggestions.

Step 1: Description of the Watering Technique

Although it took me six months to figure this out, the technique is extremely simple. First, I decided not to use any water from the kitchen for this gray water system, because of the difficulty of filtering out food particles. This system exclusively uses water from our clothes washing machine, which does contain a lot of lint, but that is easy to filter out. NOTE THAT, FOR HEALTH REASONS, IT IS NOT RECOMMENDED TO WATER VEGETABLES WITH GRAY WATER (fruit trees are OK though).

Drip irrigation systems water individual plants with little parts called "emitters" that allow the water to drip out. They are specially designed to not clog with roots or debris, but they require a fair amount of water pressure to operate and everything I have read about gray water systems warns that emitters will become clogged if you try and put gray water through them. However, there is another part, frequently used in drip irrigation systems that is the key to my system. It's called a 'barb x barb" connector and you can see a picture of one here (I'm not trying to endorse this vendor, it's just the first photo I found on the web). The barb x barb is made to connect a 1/4" diameter extension hose to a larger main line. In my system, I just put one of these barb x barbs next to each plant that will be watered. The first photo below shows one of  these "barb emitters" in action.

Each barb x barb has a hole that's maybe 1/16" in diameter, and this is large enough so that it won't clog (at least they haven't clogged after the first few months of use last summer and fall). In my first version of the system, I put the barb emitters at a slight upward angle, like in the photo. There were two problems with this: First, in some parts of the terrain, the pressure became low enough so that having the barbed emitter pointing up led to low or no water flow. Also, one of the nicest things about drip irrigation systems is that it delivers the water underground, so you get less evaporation. Putting the barb emitters straight down, sticking into the soil, would help the gravity/pressure problem and also the evaporation problem. However, just sticking the barb emitter into the soil could lead to clogging with particles or roots.

So, my second version goes as follows (see photos 2-5 below): I insert the barb x barb into the hose pointing straight down, then I wrap the middle section of the barb x barb with adhesive foam weather stripping. I then use a wooden dowel to poke a hole in the soil just under the barb emitter. I take a 3" length of irrigation tubing, fit it snugly over the weather stripping, and insert the tube into the hole in the ground. That way, the barb emitter has an empty space below it that is kept open by the tubing. I have had some of these in place since last fall and soon I'll check them to see if they are still working. Overall, I think the second version is a better idea, but there's something really gratifying about seeing the water squirting out of the above-ground barb emitters.

***UPDATE - the weatherstripping didn't hold up very well over the winter, so I'll need to find another way to plug up the hole. For now, I'm just leaving them - I have decided that pointing the x barb x straight down doesn't work in the long term, because the hole always fills up with soil, even when I put a piece of irrigation tubing inside the hole. Therefore, I recommend just having these "emitters" at an upward angle, as shown in the first photo.

Sometimes I don't have the main irrigation tube very near a plant. In those cases, I just insert a barb emitter nearby, and then insert a piece of 1/4' tubing to bring the water flow right to the plant (which is what barb x barbs are meant to do).

Step 2: Materials

Drip Irrigation Hose
1/4" irrigation tubing
32 Gallon Plastic Garbage Can
barb x barb connectors (one for each plant you want watered)

For each branch in your irrigation system:
-3/4" male to 1/2" female PVC pipe thread adapter
-1/2" male pipe thread to irrigation hose adapter
-3/4" metal nut
-3/4" rubber washer (or an old bicycle inner tube for DIY)
- 3/4" hose clamp for attaching the irrigation tubing

-One or two mesh strainers or any fine screen for a lint filter

If you need to move water more than a couple of feet uphill from you washing machine:
-sump pump
-sump pump hose
-5 gallon bucket

Step 3: The Holding Tank

Water exits the washing machine and is transferred to a holding tank, a 32 gallon plastic trash can, and from there it flows out into your garden with just the force of gravity. In my system, the water from the washing machine travels through a length of sump pump hose that enters the tank through a hole near the top.

In my garden, I have the tank about 2 feet off the ground, sitting on a wooden mount in the corner of my backyard fence. I think the actual height of the tank could even be lower and it would still provide enough pressure to deliver water everywhere in the garden. Having the water flow more slowly may be more like a drip irrigation system (though it will never get that slow), but having the water flow more quickly will clear debris from the tubes better. I don't know what the optimum flow rate is for this system, but I can tell you that my system has three irrigation branches with a total of 55 barb emitters and it takes just a few minutes for 20 gallons to flow out.

Note that plastic garbage cans are susceptible to UV damage from the sun so, for better longevity, try to keep your can in the shade. Mine is in the SW corner of the yard and I have a square piece of wood as a top, so the can gets very little solar exposure.

Each branch will have its own outlet from the can. Each outlet is made in the same way that I made watertight connections to a 32-gallon can in one of my other instructables. The only difference is that in that project, I used 5/8" connectors and in this one, you only need 3/4". So, instead of cutting a 5/8" hole in the can, just cut a 3/4" hole. Also, I have found that you don't really need rubber washers both inside and outside of the can. One washer on the outside, squeezed between the PVC adapter and the can wall, seems to do the trick.

After you've put in the connection, screw in the elbow adapter, applying teflon tape to the threads first, and then use a small hose clamp (also with teflon tape around the adapter) to attach the end of your irrigation tubing to the tank. You may want to also insert a valve in each line. This could be handy if you want to water some parts of your garden more than others, or if you want to store water in the tank before releasing it to the garden.

Step 4: The Plumbing

If, like most people, your washing machine is in your house, at least 6 or 7 feet higher than your garden, then you can run a hose directly from your washing machine to the top of the holding tank. If that's the case, then you can skip steps 1 and 3 below. Instead, you'll want to run a hose (not garden hose, but something of wide diameter, such as washing machine hose, or sump pump hose) to your holding tank. If the distance from the washing machine to the tank is not too long, you can even have the washing machine pump the water uphill a couple of feet.

1. My washing machine is in the basement, about 6 feet below the garden level and maybe ten feet below the top of my holding tank. So, unfortunately, I need to use an electric water pump to move the water some of that distance. I use a submersible sump pump that cost around $60. First, I have the washing machine hose connected to some sump pump hose, out through a hole in the wall of my house. I measured the electricity that the pump uses and it's about 20 Wh for ~40 gallons of water.

2. The water exiting the washing machine hose passes through a piece of fiberglass window screen, which catches most of the lint from the laundry water, to a  gravel filter in a 5-gallon bucket. You can't have too much filtering of the water, because once debris starts accumulating in the system, the performance starts to degrade. I became lazy about the. Filtering for a while and I ended up having two flush out the entire system.

3. The bottom of the gravel filter bucket has an outlet that passes the water through a mesh kitchen  strainer into a second 5-gallon bucket inside of which sits the sump pump. The pump has an automatic float switch, so as the washing machine empties into the sump pump bucket, the pump turns on when the water level gets high enough. The outlet of the sump pump has another length of hose that travels across my yard and up to the top of the holding tank. I have a final sheet of fiberglass mesh that catches any debris still remaining in the water.

Step 5: Planning and Laying Out the System

Before you start building, you should decide where is the best place to put the tank and  map out where in your garden you will put the irrigation hose. This is similar to planning a drip irrigation system, except that you will have to take gravity into account. If at all possible, you want to avoid making the water in the tubes go uphill, although my system has one or two small "humps" and it still seems to work OK.

I made a sketch of the locations of my plants and the paths for my irrigation lines, and then marked where I wanted to put in barb emitters, sometimes giving larger plants two or three if they require more water. This took a while, as I wanted to choose the simplest paths that would pass by as many plants as possible. I then followed my sketch and  laid out the irrigation tubing in the garden and staked it down with U-stakes. Note that each branch of your system should have its own outlet from the holding tank. Initially, I had three branches coming off of one outlet and I found that they competed with each other for water pressure (the branch with the most slope won).

Now it's time to insert the barb emitters into the irrigation line(s). First, decide if you're going to have your barb emitters pointing at an upwards angle (or maybe just horizontal), or if you want them to come straight down (my version 2 technique), or maybe a combination of all three, which is what I currently have.

I have a special tool that pokes a hole in the tubing. The barb x barbs are kind of difficult to push in, so I made a simple tool for that - a piece of wood with a hole for one end of the barb x barb. It gives me more leverage to push them into the wall of the hose (see Step 2).

If you are using version 2 emitters, then you'll have to follow the installation instructions from Step 1 for each barb emitter.

Try out your irrigation system to see if you get good flow to each plant. You may have to alter the terrain a little bit if you have some uphill sections that are lowering the pressure.

Step 6: Using the System

You'll want to purchase some laundry detergent that is suitable for your garden. There is plenty of information on the Web about this topic. The first one I used may have caused an Abutalon plant to become sick (I'm not certain), but all of the other plants in the garden seemed to do fine with it.

So far, the only maintenance necessary is to clean the lint filter every few loads of laundry. Like all irrigation systems, the tubes and barb emitters should be checked periodically for damage or blocking. I need to take a look at my version 2 emitters and see if the hole beneath them stays clear over time.

March 28, 2010
It appears that the adhesive weather stripping in the version 2 emitter holes did not hold up well over time. I think the idea of plugging the top of the hole is a good one, but I'll have to come up with another material. For now, I'm just leaving the top of the hole unplugged.

One issue I have is that I don't know which plants are receiving more water and which less. With emitters that point straight out or upwards, it would be possible to measure the flow rate, but that would be more difficult with the down-pointing ones. I guess I'll just have to keep a close eye on the plants and add more emitters to plants that seem to need more water.



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    20 Discussions


    1 year ago

    Have been using washing machine water (gray water) for almost 30 years on everything including vegetable & fruit plants. The soil filters the water and the roots absorb the filtered water. If you choose to use environmentally safe detergent that is fine as well but I have used all sorts of detergents and have never had any issues. The detergents actually assist in fighting pests. No ants, aphids or anything else. My red crawlers (earthworms) are very healthy. The vegetables and fruit trees and plants have deep green foliage. And you do save quite a bit on your water bill. Happy Harvest...


    3 years ago on Introduction

    Hello, thanks for the post. Looks like a good system. As you've seen, one of the problems with using an open-flow type drip system like you have is that there are pressure differences due to length of pipe and elevation differences. Seems like maybe you've solved this problem, but another idea is to use 1/8" poly tubing as your emitters. In the early days of drip irrigation, pressure would be regulated by using different lengths of small poly. Friction in the small poly would cause back pressure, and accordingly, you could regulate pressure by changing the length of the small tubing coming off of the 1/2" poly. You would still have an open tube which would minimize clogging. The distribution tubing would have to be small diameter so that there would be frictional pressure loss. The down side of this, of course, is that you now have longer pieces of spaghetti tubing everywhere! Anyway, thanks again. I may look into doing something like this!


    4 years ago

    Now that we are in the worst drought season , is so nice from people like you to share with us , how to use the gray water instead to let it go, beside saving water we are saving Money !!!


    9 years ago on Introduction

    Wow that's really cool!  I wish i could use this on my veggie garden, but like you mentioned - not a good idea!!  thanks for sharing

    3 replies

    Reply 4 years ago

    You can use it on your veggie gardens if you use environmental friendly soap ;-)

    More recently, someone who knows a lot about gardening told me that she thinks it's OK to use gray water for a vegetable garden as long as you don't spray it on the leaves (i.e. as long as the water is delivered to the base of the plants. If that is true, then perhaps you could use this to grow vegetables. I think the jury is still out about what is actually safe or not safe to do with various types of gray water.

    I have been using greywater in my ornamental AND edible garden for some time now, but I do it with soaker hoses and drip systems so it actually does not get on the plants. Plants do well and I do not really see a problem with health issues, considering what I know gets into my greywater which basically is detergent i.e. liquid soap for the dishes and a mild non bleach soap for clothes.

    I do not care that much about foodscraps in the grey water other than that it might block my hoses. Therefore most of my grey water from the kitchen goes to a basin in which food scraps sink and it is pumped into the garden through a filter.
    My bathtub empties on the lawn and the trees whenever I pull the plug.

    I live in a fairly wet country though, but especially in the summer i would consider it a waste to just let it flow down the drain to the summer.

    Cost is part of the equation as water is cheap here. Most of my bill is because of taxes and levy's so I cannot make my solutions to be expensive. To give an example: By using my water wisely, I have been able to cut down from 60 m3/year to 30 m3/yr and now 15 m3/year. However, every m3 saved, saves me about 1 euro on my water bill.

    If I were to buy a rainwaterbarrell to collect rainwater, that would set me back about 200 euro's (yes, expensive) for say a 150 liter barrel. I would need to save 200 m3 water to even break even, which would be 1333 full barrels. That is just not worth it.

    Using graywater with relatively cheap hoses and a 15 euro pump is therefore more rewarding. For storage I use some 5 euro cement buckets that can contain I think 100 liters. I have seen some 1000 liter vessels that apparently are used to store foodstuffs and those come at 10 euro, at the local ebay but these just take up too much space. Yet, I think about buying one and just digging it in.


    FYI: The Laundry Drum has been superseded by the Laundry to
    Landscape system. This system takes advantage of pressure from the washing
    machine pump to send the water to several outlets up to 100ft away from the
    machine. It can also serve outlets up to the height of the top of the machine.
    There is an Instructable on this system at: https://www.instructables.com/id/Laundry-to-Landscape-Greywater-System/

    The web information hub, and an instructional video for this
    system are at http://oasisdesign.net/greywater/laundry/.


    5 years ago on Step 4

    You’ve got a good little system working and it sounds like it costs practically nothing to put together. I would disagree that the gravel filter is an unnecessary component – it’s surprising how grit and dirt can find their way into things and cause clogged-up pipes and blocked drains. Of course we can’t avoid these issues no matter how well a filter system we put together, but every little bit helps reduce the amount of time we spend dealing with it.


    7 years ago on Step 6

    Hi I am so glad to hear other people are doing this. My washer sits on a hill inside our house. The garden it waters is outside the wall and the garden is all ornamental and all runs downhill. We connected a short regular garden hose out the wall exit, then my husband added a soaker hose through the whole garden away from the house but weaving through all the bushes. We do laundry one day a week, usually one dark load, one white load. All the gray water is plenty to keep all the plants on the north side of the house perfectly watered. This is great in S. Ca. When it gets hotter out, we have a small pump we put in our bathtub, and pump all that gray water out to the front yard using a regular hose, and running it out to a sprinkler head on the lawn or in the flower beds. All our garden foods are watered w/reg. water. We have cut our water consumption by 30-40% by using gray water systems on both sides of the house. We also have exchanged out much of the original grass areas for indigenous plants that are drought tolerant!
    Thanks for sharing how to do it if you are not as lucky as we are and need pumps to lift water up and out of the house! Ours was also just trial & error, and seeing what worked and expanding it where we could! Hope you get others on board!
    We heard of some of it through a book about using gray water called "Damn Nation' also a good source for building gray water systems.


    8 years ago on Introduction

    Here is my question................By using the washer used water......... I read through this and only see where it states using a certain washing compound so as to not harm the plants. Did you happen to come across any filtration system during your ventures of researching? The reason I ask is......if your spouse or a person uses bleach or some other agent in the machine then your plants may want to vine their way to you for payback. So........knowing that most chemicals will separate from the water over some time.......maybe helping this process along would develop a cleaner water supply. Not sure if a salt filter or charcoal type would work enough to clean the water. I do know the grass sure will grow and the weeds love it when the washer water is dumped onto the ground.

    2 replies

    That's a very good question. First, we never use chlorine bleach in our household, because it is so toxic and bad for the environment. Instead, we use a non-chlorine bleach on our laundry and that doesn't seem to bother the plants. Now, sometimes we do need to use other detergents for "special" loads of clothing. In that case, the system has a pair of ball valves that divert the water down the regular sewer drain. I should add this information to the instructable. As far as having a chemical filter, I don't have enough knowledge of chemistry, but I think the easiest solution is to have a set of diverter valves and everyone in the household should know to send the water down the drain whenever they are not going to use a plant-compatible detergent.

    I don't think chlorine bleach is necessarily bad for the environment or plants.

    Here is an explanation on chlorine bleach: http://www.howstuffworks.com/question189.htm

    And here is an explanation on the rinse cycle neutralization of chlorine bleach: http://www.clorox.com/blogs/dr-laundry/2011/10/17/neutralizing-rinse/

    Chlorine is in our water. We drink it. And water plants with it. A chlorine bleach cycle will probably be safer than detergents, which can be more harmful due to its chemistry of bonding to dirt/grease. I would drink a chlorine cycle glass of laundry water than a detergent cycle. Living things can tolerate everything in moderation - arsenic for instance.


    8 years ago on Introduction

    What I have read about graywater is different. They say if you use it, make sure it stays off the plant and is aimed at the ground. It is only when the water gets on the plants that it might be hazardous to people and especially if you do not properly wash the food before eating. Think about it...compost has bacteria. It is constantly used to feed the plants. Also when you look up what to use and not to use in composters, they warn many things will make a strong odor and attract predators and insect pests.

    Any clean watering system can even be a problem is you have it hooked into the house watering system without a backflow valve. With appropriate measures it is safe to use bath and shower water for watering if you do not use chemicalized hair and body care products and aim the water to emit gently (so it doesn't splash) and apply to the earth and not the plant itself..


    8 years ago on Introduction

    no need for the barb, just drill through the black poly with a 2 - 3 mm drill bit. At the end of the run of poly put an elbow & a short length (20 - 40 cm) of poly pointing straight up. This will provide a bit of back pressure so all holes will emit water. The run of the poly needs to be flat to slightly down hill. Easiest filter I've found for the amazing amount of fluff coming out of the washing machine is a length of pantihose leg tied over the outlet hose. It needs to be changed every three or four washes.


    8 years ago on Introduction

    Reading various systems. Your tank looks nicely set up. I want to know what is that beautiful plant that is growing under your storage tank in step 3? I would love to get one of those growing in my garden.

    2 replies

    Unfortunately, I don't know what the plant is called. The flowers are a BRILLIANT orange and they last for only a week or two in the spring. I've seen it in our local nursery, so I'll post the name if I find out.


    Clivia. We have some ourselves here in Waitakere City (two more weeks 'til we're part of the Auckland "supercity" :[ ).


    8 years ago on Introduction

    Thanks for the response, if your plant blooms again could you get a close up pick and post it. I might know what it is but need a closer picture of the blossom. Would greatly appreciate it. Again, nice job on the tank and all.