Now that we having running water in the house – and hot water no less, we decided it was high time to upgrade our grey water filtration system. Originally, we were granted planning permission after having a study completed of our land which ensured that it was suitable for a ‘Lit De Roseaux’, or reed bed system of filtration. The study outlined the exact measurements, tanks, locations and size of the filtration system. This was out of our reach in terms of cost and so we have essentially made a carbon copy of the system but utilising a different type of tank; namely a cast iron bath tub.
Although risky in terms of being signed off, we are happy to take that risk and feel confident backing up the system we have installed in terms of it meeting the exact requirements of the square meterage of filtration space, the types and amount of plants used, the materials under the reeds and the cleanliness of the water.
You might ask why we would take this risk, and you’d be right to. I know I did. The outlined plan from the company who undertook the study is actually for a black water system, which we do not use it for – choosing instead to compost our dry toilet contents. Composting of the toilet is totally fine with our local waste office. Meaning the proposed system was already overkill for the job in hand. We also ensure that no harsh chemicals go into our grey water. I make our cleaning products and use all natural soaps and shampoos. The harshest ‘chemicals’ that go down are diluted vinegar and bicarbonate of soda. These reasons gave us the impetus to implement our own slightly amended version of the water filtration system.
First item on the list was a cast iron bath tub. Enter our buddy Paul, who was working on a bathroom at the time and happened to mention he was throwing the large, old cast iron bathtub into the skip for his client. My hand was eagerly raised!! Paul so kindly transported it to our land, enabling us to chow down with the rest of the project.
Here is a picture of our back-of-a-beer-coaster design:
The general idea is to take the grey water from the house (kitchen, bathroom and urine), run it through a grease trap before it enters into the amended bathtub. By sectioning the tub into four (using a membrane) and forcing the water to go up, down and over, the length of time the reeds have to do their filtration thing is extended. At the bottom of the tub and in each section, we placed broken red ceramic tiles, a hangover from building the house. The tiles are untreated, porous ceramic and perfect for creating more surface area where organisms can grow. Each section was then filled with a mixture of 0-30mm gravel followed by a layer of medium-sized, highly porous volcanic rock. The porous nature of the rock is very important as it provides a breeding ground for organic matter and bacteria to take root, from which the reeds can feed, thus creating the natural filtration. Several layers of each were put down ahead of a final layer of gravel.
In the first section of the tub, we planted in standard reeds, which are sometimes used in isolation in some systems, but we decided to mix it up a little, adding in a variety of plant species to the next three sections, in line with the plants recommended by the local sanitation department here in the Charente. It has been a pleasure to watch the different plants flourish, flower and die back over the course of three seasons. The filtered water is now directed into the base of our HugelKultur vegetable beds, providing clean waste water to all our little veggies. I came across a plethora of designs for this final stage on t’interweb, including some standing beds which grew year-round salad leaves. I thought this could be a lovely idea in the future, but went for the easier option for now.
Regarding the efficacy of reed bed system and the quality of the waste water itself, we have been delighted with the outcome. It never smells and the plants only continue to flourish, a clear sign that this, now very passive system, is just working. If anything, I think I may have planted a few too many plants into the bathtub; 20 in total! They seem to come at go at differing times of the year, which is great, allowing some to take precedence over others before giving way to their buddies.
Here are a few pictures of the building process:
We both love this system, the passive, circular nature of it is immensely satisfying. From the water falling naturally on our roof, us then diverting into the house for a little bit, for it to then come back out via this filtration system and end up where it would have done anyway, feels like it is truly working in line with nature and not outside of it. This simple system really is far greater than the sum of its parts… including the bonus pretty pink flowers throughout the summer 🌸