How to Build a Grey Water Wetland

Resilient Life Public Resilient Life
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How much almost clean water is wasted down sinks, washing machines, and showers? At my house, my wife and I use thirty to forty gallons a day, but the typical household can use up to 200 gallons. It is poor house design to not take into account reusing grey water in a safe effective way. I decided to rectify this situation at my own home. Please bear in mind that you may have local codes and ordinances against grey water systems.

1. The first step required some indoor plumbing to route my sinks, showers, and laundry into a pipe that could be sent to the wetland outside. Also, a valve was installed to allow me to turn the system on and off, as in the winter the plants will not perform their filtering function when they are dormant.

Valve to Turn off Grey Water in Winter

2. Trench the grey water PVC pipe to your wetland area. This pipe should gravity flow to your site.

Grey Water Exit from House

3. Size your wetland area. According to the permaculture book, Gaia’s Garden a wetland area should be able to hold three days of grey water. A busy household running 200 gallons a day would need a 4 foot by 10 foot wetland that is 2 feet deep. This size would hold 600 gallons. Even though my household uses a fraction of that amount, I went much bigger with a 10 x 10 that is about 18 inches deep. I wanted more volume, because I wanted to make sure that by the time that water got into my fish pond the water was really clean. It may be overkill, but it wasn’t that hard to dig a bigger hole when you have an excavator on site.

4. Dig your shallow wetland pond. The shape is unimportant, so choose what is practical and what looks nice. Make sure the floor is level, as you do not want material accumulating on one side.

Underlayment and Liner Installed

5. Add the pond underlayment. This is important as cushioning from any rocks making holes in your liner. Add the liner and hold in place at the top with rocks.

6. Cut small slit in liner to allow inlet PVC pipe to enter wetland. Liner should fit snugly on pipe. Seal liner to pipe with pond sealant.

7. Install inlet pipe with a tee at the bottom of the pond. Install perforated PVC across the bottom of the wetland to spread the grey water as it enters the wetland.

Inlet for Wetland

8. Set your spillway exit point and depth. Make sure it is at least 2 inches lower than the pea gravel level, so mosquitoes do not breed. I used a PVC pipe through the liner as my spillway exit point. I put a grate on the side with the pea gravel, and I put a larger rock in front of the grate, so it stays clean.

9. Fill in 6 inches of 1-1.5 inch round river rock at the bottom. Dump it in slowly so you don’t damage your piping. Then fill the rest of the wetland with pea gravel.

Wetland Exit Pipe

10. Send you cleaned water to a useful site. This could be a swale, a pond, a rain garden, or any other site that could benefit from the regular water. I sent my spillway to a silt pond, that overflows to a fish pond.

11. Add plants to the wetland. In the video below I mention that I planted reeds for my cleanup plant. To be specific, it was variegated reed canary grass. This grass can be invasive. If you use COMMON REEDS, Phragmites australis, the roots can puncture a liner. I would recommend NOT using this type of reed. Incidentally, I recently pulled out the reed canary grass because of their invasive nature. I was concerned about the plant spreading into the bordering food forest, as this plant can grow in water and land. I replaced the plants with:

Juncus Effusus Spiralis: Corkscrew Rush
Scirpus Tabernaemontani: Zebra Rush
Iris Pseudacoris: Yellow Iris (This plant is not as good as the rushes for cleaning the water, so it cannot be a major part of the wetland)

Grey Water Wetland

//www.youtube.com/embed/p-usRfEPG10?list=PL0ZP4j0ePR4ab4rc_3uLaGcloO7Bd_AY4

See part 1 of the installation of a grey water wetland system that overflows to a lined silt pond, that overflows into an earthen fish pond.

//www.youtube.com/embed/4ZNGrJTeCEM

See the final part of the wetland and silt pond project. Also, see a very nice waterfall spilling into the feature fish pond.

In the video, I mention that I planted reeds for my cleanup plant. To be specific, it was variegated reed canary grass. This grass can be invasive. If you use COMMON REEDS, Phragmites australis, the roots can puncture a liner.

~ Phil Williams

Phil Williams is a permaculture consultant and designer and creator of the website foodproduction101.com.  His website provides useful, timely information for the experienced or beginning gardener, landscaper, or permaculturalist. Phil's personal goals are to build soil, restore and regenerate degraded landscapes, grow and raise an abundance of healthy food of great variety, design and install resilient permaculture gardens in the most efficient manner possible, and teach others along the way.

This is a companion discussion topic for the original entry at https://peakprosperity.com/how-to-build-a-grey-water-wetland/

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Please check with your state's invasive plants list before deciding what to plant.  Iris pseudocoris (yellow iris) is on the Connecticut invasives list, but it might not be invasive in some other state. 

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The whole idea of "invasives" is a major bone of contention in permaculture circles.  Personally, I fall on the side that there is no such thing as "invasives" – instead you have opportunistic plants, species that are evolved to establish themselves quickly and proliferate under certain stages of succession.  For example, purple loosestrife is often classified as "invasive," but in reality it is just evolved to do very well in areas of high nutrient concentration.  Autumn olive is "invasive," but in reality it moves into degraded areas taken back to ground-zero succession, establishes itself quickly, and pumps nitrogen into the soil through its roots (which eventually improves the soil and causes succession to pass it by).
Much of what is published by states as "invasive" lists is highly subjective.  It's better to know the basic characteristics of a plant and either work them into your design accordingly, or exclude them based upon those characteristics.

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What about Phragmites which restricts water flow in wet areas, creates monocultures, and out-competes native cattails, shrubs, and grasses? I've seen acres and acres of nothing but phragmites. Landscapes that use to be a beaver floodplain which provided food and habitat to numerous wildlife species, is now a limited, solidified wetland. Not ideal.
Also, have you ever seen Kudzu? What a nightmare. I've had the pleasure of killing acres of it and it is something we New Englanders are so fortunate to not have to deal with. It smothers everything! Trees, understory, EVERYTHING. It also creates habitat for a little beetle call the "Kudzu beetle" that stinks and burns something awful when squished on your body. I hope to never have to see and walk through Kudzu again.

I'm a big fan of Autumn Olive (I would plant it), but it can be very aggressive in edgy areas. Purple Loosestrife is okay as my honey bees love the loosestrife crop. I also have a theory that the introduction of honey bees are one of the reason why loosestrife and some other invasives have been so successful. Not a lot of research on that though.

The most important part of recognizing a species as invasive is that they are non-native plants and that replace, out-compete (lack or pests or predators), and can even alter the health of the soils and the surrounding environment. Some blend better than others like burdock or bittersweet nightshade. Plants like phragmites, knotweed, bittersweet, and kudzu are bad news invasives. 

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I would add that Norway maple, although it is a slower motion catastrophe, seems to be very successful at invading hardwood forests here in the northeast and then reaching the canopy and crowding out other species including understory species.  I'm not sure it will be able to be quite so dominant in existing mature forests, though.
Various honeysuckle and buckthorn species seem to be able to totally take over the understory of at least some moist forests.

Multiflora rose seems to be aggressive when the forest is young, but fades as the canopy matures.

Burningbush and Japanese barberry never seem to become dominant with the possible exception of highly disturbed woodlands.

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Yes, Norway maple as well as black locust are really taking over early successional New England forests. Both make a great crop for honey bees, but they are absolutely replacing the native canopy.

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It's not uncommon for the plants that do the best job of cleaning the water to also be aggressive and on invasive lists. I think it is important to have some understanding of growth habits and how you plan to manage what you plant. I agree with wildlife tracker on Autumn Olive. I also like Black Locust. These are examples of plants that are welcome to invade my property. Tree of Heaven is another story.  

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https://www.eomega.org/omega-in-action/key-initiatives/omega-center-for-sustainable-living/the-building