How to Build a Grey Water Wetland
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.
2. Trench the grey water PVC pipe to your wetland area. This pipe should gravity flow to your site.
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.
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.
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.
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)
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.
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.