Filter Your Laundry Graywater With Marsh Plants!




About: Ordinary guy with no special skills, just trying to change the world one backyard invention at a time. See more at: On Twitter - @300MPGBen and at

A while back, I started using greywater, waste water from my clothes washer, to flush my toilet. The system works well, and saves TONS of water, but I still wanted some way to filter the water first, preferably with a biological system.

I keep a large aquarium, and I also compost, so I thought that some of those same principles could be applied in my laundry room.

So, I converted my laundry tub into a constructed wetland!

To get  started, you will need:
Space next to your washer
A laundry tub
Drain Pipe
Hole Saw/Drill
Sand, pebbles, stone, dirt
Landscaping fabric
Wetland Plants
Your wife's permission!

Step 1: Work Area - Tub Space

To get started, find the space next to your clothes washer.
In this space, I originally had a wash tub, but replaced it with a large barrel to hold laundry water. The original water-lines and drain are still there.

In this case, we are NOT going to use the drain, but rather, install a new pipe that leads to a water storage unit.

Measure where the center of the drain is on the laundry tub, and then mark that same distance on the floor. Drill a hole through the floor there (making sure a floor crossmember isn't directly below) with a 2" hole saw.

Slide a drain pipe through the hole. If you have a full basement, you can slide the pipe in from below later. If you only have a crawlspace, like I do, you will have to put a short piece of pipe through BEFORE you install the laundry tub.

Step 2: Install the Wash Tub

Put the wash tub back in next to the washer.

Hook up the water lines to the faucet.

Glue a threaded connector onto the end of the new drain pipe, so that it can thread directly to the washtub drain. 

Thread the new pipe into the bottom of the wash tub.

Step 3: Install Layers of Filtering Media

We will now layer materials in the tub.

First, hop in your home-built electric car, and drive to the local landscaping supply store. Get yourself some big stones, little stones/pebbles, sand, dirt (if you don't already have some,) and landscaping fabric.

In my case, the cheapest bulk way I could buy materials was by the 5-gallon bucket, so I brought a few with me. 

Layer up materials in the bottom of the sink in the following order.
1) Big stones over the drain (to keep other smaller things from getting in there and clogging it up.
Then add a small piece of landscaping fabric over that, pinned-down by a few stones.
2) A layer of the big stones. One or two stones deep is fine. This is for good drainage.
3) A layer of pebbles. (It should make a more or less solid layer. The pebbles should be big enough to not fall through the spaces between the bigger rocks.)
The landscaping fabric. (My piece was about 3' by 4'. Fold the edges like a Chinese take-out container)
4) A layer of sand, about 2" thick
5) A layer of dirt, about 2" thick

The landscaping fabric is there to prevent the sand from working its way down into the drain. Since the fabric is floppy, you will have to hold it back out of the way while you add the sand and dirt. If you have 2" spring clamps around, those work well to pin the fabric back too.

Step 4: Plants!

Now it's time to get some plants.
My plan was to use plants that like to be wet pretty much all the time. I have plenty of marsh plants in my area, including my front and side yard, so I just grabbed a shovel and some buckets.

You might want to visit a gardening center that carries pond and wetland plants and see what they have available.

I dug up some marsh grass and cat-tails. The marsh grass has an AMAZINGLY thick mass of roots, which should work well for filtering.

Place the plants in the tub, and fill in around the edges with a little extra dirt. I also added a few other little plants around in there.

Step 5: Hook-ups

Now, you can put the washing machine hose back in to the laundry tub.
When doing laundry, the waste water will irrigate the plants, filter through them, the sand and gravel, and down the drain to the other components of the existing greywater toilet-flushing system.

Make sure to use an eco-friendly laundry soap, and don't use any harsh chemicals, like bleach.
I do still have a dedicated laundry drain right behind the washer. If I did need to, I could always temporarily switch the drain hose back that original drain.


Step 6: Video Demo

Here's a video, just to show you a little better what I am trying to do with this system.

I have also started a blog on my home water conservation, solar power, gardening, and other ecological adventures at 

I updated the system to a 50 gallon stock tank tub. That holds more water than the smaller tub that I had, and it "reaches" from the drain out to my crawlspace hatch, so I can see what the water level is.



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30 Discussions


We frequently wash with very hot water, how do the plants handle the heat? Do you just not wash with hot water?

1 reply

We just wash with cold water. I suppose that if you needed to, you could have a tank that the wash water empties in to and stays there for a while as it cools. (If you live in a cold climate, that heat would then go to at least help heat your house a little.)
You could then open a valve and drain the now cooled water down to the plants.


7 years ago on Step 6

Makes me wish I had a washer to experiment with this idea, great job.


7 years ago on Step 6

What if you simply filtered the water to use again in your washing machine? It's hard to tell if the water is clean enough but I imagine the vegetation and the fabric clean out any particulates you may have from washing really really dirty clothes and other than that it would just be clean water with maybe a hint of soap.

then you could just use the same water over and over and over again for washing clothes, or if you wanted to get really fancy you could use a valve or something and use the water for the toilet occasionally (when you wanted to change out the water)

either way awesome idea


Reply 7 years ago on Step 6

No. No mosquitos.

There was one time when I was sort of redoing the plants, and I just had some landscaping fabric in there. It would get wet and not dry. I got fruit flys for a few days because of that.

With the regular setup of plants over sand-filter, everything is fine.


9 years ago on Step 6

For the threaded port on the side have you thought of modding the plug to allow the Pex pipe to go through it?

2 replies

Reply 9 years ago on Step 6

I could do that, but it is just so easy to simply put the pex tubing over the top.

The other odd thing is that the drain plug really isn't all the way to the bottom, I can actually get the tube lower than it would be connected to the drain.

That drain plug might make a good spot for an overflow. Instead of running a pipe straight out from it, I would put an elbow on there and have pipe go up to just short of the top of the  greywater tank, then over and out.

I would just need to make sure there is an air break so that it wouldn't siphon ALL the water out if the tank overflowed.


Reply 8 years ago on Introduction


I did end up doing exactly what I said above.

One time, my wife was doing laundry and not paying attention at all, and flooded the crawspace a bit...

I put a PVC pipe going into the drain port on the side of the tank. That splits up to a manual drain with a valve on it, and output to the pump, and a pipe that goes vertically up to just shy of the top of the tank, with a tee that's open to the air to prevent siphoning.

Should the tank get too full ( too many loads of laundry in a row for example... ) it will start going out the overflow drain before it would run over the rim of the container.

I have still not added any sort of "automatic filling valve" to the system. The single biggest idea of this system is to save water, and keep it as simple and passive as possible.

Should the toilet get flushed too many times compared to how much laundry we have done, the water level can drop too low. On the rare occasions that it does, I just run a little water from the laundry tub faucet straight down into the graywater tank...... Then I notice it was about time to do a load of laundry anyways.....


Reply 9 years ago on Introduction

 Seems ok so far. I haven't had it set up like this too long yet though.

I believe soaps are typically high in phosphorus, which the plants should tolerate pretty well (this is what causes algal blooms). But the plants are really there to provide microenvironments with high oxygen around the roots. These microenvironments and the ones that form around and in between the pebbles provide oxygen for the aerobic bacteria that do the actual work of breaking down the greywater.

I use an eco-friendly, all-natural soap (locally made!) and the plants have no problem with it.

As QuestionConvenience just stated, what this is all really about is setting up the right environment for plants and microrganisms to thrive to help prevent the formation of bad bacteria and keep particulate matter out of my pump.

I'm just trying to imitate the way that nature uses wetlands to clean and filter water.
So far, it's been working very well.


9 years ago on Step 6

 Right now, the cat-tails are over four feet tall!

I measured, and when they were shooting up, the grew faster than an inch a day!

The marsh grass isn't doing as well. At first, it shot right up, and looked green and healthy. But then it flopped over and looks to be turning yellow.

Other plants are now growing in there as well. I am happy that these "weeds" seem to be springing right up!

The water in the holding tub stays very clean and clear-looking.

2 replies

Reply 8 years ago on Step 6

Do they need much light? Usually a laundry room doesn't have much.


Reply 8 years ago on Step 6

My laundry room only gets good light late in the day.

I did later replace the marsh plants with "spider plants" and some other plants that grow well in lower light.

I also installed an LED strip light under the upper cabinet, and had that on a timer. It takes almost no electricity, but still gives the plants some light. It's mostly just for winter use when the days are so short.


8 years ago on Step 5

Is bleach a harsh chemical? In the concentrations used for laundry, the plants may not mind it that much.

1 reply

Reply 8 years ago on Step 5

I get itchy skin if bleach is used on my clothes.
Same with chlorine pools.

Half the problem is that people tend to use TOO MUCH of household chemicals.

For me, it's just easier to not use them at all.


8 years ago on Step 6

I love it !!!!!!! I do have a question though . I have been tryingto come up with a simila way t filter my grey water for watering our garden. This woudl be a large scale filtering as my garden is 3 acres. We use eco friendly soaps (challeneg to convert wife) for awhile now , but still at times use bleach. Do you have any advice for someone needing to double check themselves or add a measure of safety to a large water collection system? My ultimate goal is to have a system in place that wil capture all rainwater and grey water to use for watering my garden. The only thing hiting sewer would be toilet water . ANy help greatly apreciatted.

1 reply

Reply 8 years ago on Step 6

I would imagine that an outdoor "constructed wetland" would fit the bill. Check out any and all books by Art Ludwig. He has books on graywater AND constructing cisterns for rainwater holding and irrigation. Also, do a web search for Graywater Guerrillas and visit Hope that helps! -Ben