Introduction: 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.