Permaculture - Home-made filtering system for the gray water (lesson 39)

Gray water from the shower or sink can be used to water the vegetation in gardens, at least in the case when you do not use strong detergents. We mentioned this in a previous permaculture lesson. I also noted then that it is better to use it for watering ornamental plants and avoid a situation in which the water is directed at parts of vegetables or fruit that are consumable (such as lettuce leaves or berries). But what if our garden is filled almost exclusively with food plants?

Even then the use of gray water for irrigation is possible, but it requires prior filtering. The most convenient way is to buy a special filter system, but it is an expensive solution. Moreover, as permaculturists, we do not like to rely on technology in situations where natural solutions are available - technology requires maintenance, produces garbage, requires the replacement of equipment from time to time.

A much better way is to create small wetlands in your backyard that act as natural filters. This will be labor-intensive and space-consuming (much less than you expect), but the solution is essentially perpetual, and once established wetlands require almost no additional maintenance effort.

DIY step by step

Building a domestic wetland is time-consuming but quite easy. In fact, all you need to do is dig a shallow pond, fill the ground with gravel and sand, and plant all around with swamp and water vegetation.

1. Choose a place that is below the pipes with gray water. Thanks to this, gravity will allow you to transport water without the need to install a sewage pump.

2. Dig a small ditch. The wetland should be able to hold the volume of gray water for three days and be 30-60 cm deep. The shape of the purification system is not important. You can create one or more ponds of any appearance - you can easily ensure that this space remains not only functional but also has high aesthetic value.

3. Cover the whole with a plastic pond liner. If you have high clay soil in your garden, you can skip this point.

4. install plumbing. Take care of the pipes supplying water from the house and discharging it further into the water reservoir or directly to the garden. Cover the pipes and the bottom of the swamp with fine gravel.

5. cover everything with a centimeter of sand or good-quality soil and plant water-purifying plants (listed below)

6. Drain the water into the purification system. The water should be passed through our little swamp in such a way that it never completely covers the gravel from the bottom. In this way, we will avoid the additional multiplication of mosquitoes, which is especially important in regions where there is a risk of contracting malaria. It is possible (but not necessary) to install a water level control box. It is a small tank to which the gray water inlet pipe is directed. It has an upward curved outlet pipe leading to the purification system.

7. Water cleared by vegetation, microorganisms, sand, and gravel should be discharged into our garden thanks to irrigation pumps. Remember that living in cold climates where the vegetation planted around your purification system hibernates for the winter, the water is not purified during the coldest period. You should then direct it to the septic tank or sewage system, avoiding watering greengrocers with it.

8. Drain wetlands every month for 2 or 3 days to help plants take root better.

Plants that are worth using for the construction of a home purification system:

At least 60% of all plants in the tank should be selected from this group:

Bulrush	Canna Lily	Cattail
Soft rush	Reed canary grass

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The remaining 40% can be selected from plants supporting cleansing functions:

Arrowhead	Chokeberry	Comfey
Cranberry	Daylily	Elderberry
Hedge hyssop	High-bush blueberry	High-bush cranberry
Horsetail	Lotus	Ostrich Fern
Pickerelweed	Sedge	Spike rush
Sweet flag	Taro	Umbrella palm
Water canna	Yellow iris

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