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Natural water filter for rooftop rain water

About 15 years ago I read about a way to purify water without special filters or chemicals. It was a system that took water and ran it through a 10' or 15' planter with a variety of plants. The combination of plants, soil and gravel worked to purify so that water that went in one end of the planter was purified by the time it came out the other end.

If I remember correctly the system was designed by Japanese naturalist and was being used in high rise offices.

There was also a system that used a variety of plants, fish and waterfalls to purify water for a natural swimming pool. I remember that the landscape architect that was using this system commented that his mother did not like swimming in a pool where the fish were nibbling on her toes.

I'm looking for something like this to purify rooftop rain water to use the water for a small fish pond.

Any in0put would be appreciated.



Comments (8)

  • 17 years ago
    last modified: 9 years ago

    are you talking about green roofs?

  • 17 years ago
    last modified: 9 years ago

    this may be a dumb question but isn't rainwater pure as it is?
    that's why people use rain barrels-to capture pure rainwater to use on sensitive plants for one example.

  • 17 years ago
    last modified: 9 years ago

    Rain water would be clean if the air - and roofs - weren't dirty. The air contains water soluble contaminants, and your roof gathers particulates.

  • 17 years ago
    last modified: 9 years ago


    my grandfather was ingenius man when it came to rigging things up. my grandparents lived in the high mountains of oregon where the rain falls practically everyday. they didnt have running water so my granfather used the gutters of the house and a few odds and ends to set up plumbing. he put palm size gravel all along inside the gutter to prevent large debris from going down the spouts, the rocks were level with the gutter rim so all he had to do was run a broom over it when the leaves built up. he capped off the gutter spouts with mesh and filled them to the top with alternating layers of sand , fish tank size gravel, and some sort of charcol/carbon. i dont remember exactly what that stuff was. i also remember him putting a large handfull of cleaned sheeps wool before the sand to keep it in place. the bottom of the spout was at about 4ft off the ground and flowed into a half barrel. there were holes drilled into the mid-level of the barrel that hoses led off from. the backside of the house with a spout on each corner was uphill from the front of the house. so it was a simple matter of gravity to get the water into the house. one of the hoses led to a white semitransparent 50gallon plastic drum that sat in a small clearing to collect sunlight during the day. that heated the icey water enough to bathe, even if it was 20 degrees outside. the water by evening would be almost 76 degrees on a good sunny day. he also set up a similar sytem for the pigs. he used 5 umbrellas in a sort of mobile to catch water, they were all angled so the water went to a hole cut in the bottom. this drianed into an upside down milk can with its bottom cut off. it was filled with stones and wool and sand and carbon and had a mess screen on top to kep out large debris. the other end of the jug was sitting in a wood frame suspenped above a long water trough.the only part of the trough that was outside of the pig house was covered by a frame so it worked really well to keep the water clean. even for being in a pig house it was clean enough to support a population of minnow bait fish.

    as far as the plants go im sure you could ommit the filled drain and have the spout feed into some of the long planter boxes. cut a 4 inch pvc pipe in half leghtwise to form 2 long troughs and hang the planters with one avove them and one below. you can line the bottoma of the planters with materials like sand, gravel and cotton gauze or aquarium filter pads. this will trap all of the small bdebris and create a biological filter. its a mini ecosystem of microbes.
    planters should be lined in layers from the bottom:
    1 cotton about 1 inch thick(will be compressed)
    2 clean sand (aquarium grade is chemical and pollutant free)
    3 pea size gravel 1/2 ich thick -unpainted rough surfaces
    4 dirt and plants.- i prefer coconut fiber
    coconut fiber has less sedimentary debris after water runs thru it a couple times and doesnt erode as fast.

    i would think crushed pumace would be a suitable substitute for the sand and gravel, as well as any other highly porous material. you want to make homes for all the micro-organisms to create the filter. the porous material also traps small debris and the cotton or aquarium filter pads will catch small sediment and plant material that the rest missed. it will also create a large base for the microbes.
    if you want acces to the cotton make a fine mesh basket that will fit in the planter on top of the cotton, place the other layers inside the basket and when its time to change the cotton simply lift the basket out of the planter. however, a good setup will never need to be cleaned.
    you can put as many planters in a row as you can hang from the eaves of the house this way. the pvc 1 will water the planters. give it a very slight tilt so the water will go all the way to the end.drill a small hole every 2 inches or so for the water to drain into the planters the planters will then drip into the other half of the pvc which will not have holes. it will flow directly to the collection container. ie pond, bucket, barrel, fountain. you can also line the pvc 2 with plants and gravel like a long planter for added filtration.

    i have many more ideas about how to collect and filter water. i will post again another time:)


  • 17 years ago
    last modified: 9 years ago

    the water by evening would be almost 76 degrees on a good sunny day.

    Not my idea of "warm enough to bathe," but to each his own. ;-)

    You want to be careful with these homebrew schemes. If the water is for human consumption, make sure you have some way to prevent bacterial and fungal contamination from becoming a problem.

  • 17 years ago
    last modified: 9 years ago

    I think what you're referring to was written about it the early 1990's in Garbage magazine (defunct now).

    More recently, MIT came up for this for use in the developing world (and USA, too, I guess!)

  • 15 years ago
    last modified: 9 years ago

    i saw something in this inspirational GREEN film
    that was using plants, fungi, soil, fish, algae, ,and beneficial bacteria
    i myself am trying to get to the source on this topic
    i'll post here if i find out

  • 3 years ago

    Thanks for sharing! Every family deserves a water purifier. I use waterdrop for years, very space-saving and durable. Check out the link for more information.