Rain Water Collection System (possible Greenhouse Frame)





Introduction: Rain Water Collection System (possible Greenhouse Frame)

About: I'm a Multimedia Designer and Web Developer. I have a background in Graphic Design, Programming, Animation, Illustration and Sculpture. I have done freelance Motion Graphic and video work for over seven year...

Free clean water for anybody, anywhere.

Nobody should ever be without clean water. Any region in the world with a few inches of rainfall can capture that rain water, filter it, purify it, and put it to good use. My friend has an urban farm where she grows fruit, vegetables, and herbs. But there was no reliable source of water on her land and she had to have water hauled in. So I designed and built this simple structure on her land to capture, filter, and store rain water for agricultural irrigation. With additional filtration and sterilization, this system could also be used to provide safe drinking water.
Now I'm putting the plans and instructions online so that anybody around the world can build their own off-grid stand alone rainwater collection system. This particular structure is 128 square feet, measuring 8 feet wide, 16 feet long, and 8 feet 6 inches tall. We contacted the local building department and they told us that we don't need a permit for any structures less than 200 square feet.

Step 1: Posts

I used 10 foot long 4x4 posts buried 48 inches deep in the ground with concrete. The posts are spaced 8 feet apart from each other. The front posts are cut 7 feet 5 inches tall, and the back posts are cut 6 feet 5 inches tall.

Step 2: Beams and Braces

Beams are horizontal 8 foot boards that sit on the posts. Braces are the smaller 4 foot long boards at 45 degree angles that provide support.

Step 3: Rafters

The rafters are 10 foot long 2x6s with a 6 inch overhang on the low end, and about a foot of overhang on the high end

Step 4: Purlins

Purlins are long thin strips of wood that measure 1 1/2 x 1 1/2 inches and 8 feet long. They sit on top of the rafters spaced 1 foot apart. Purlins provide support for the roof pannels, as well as a surface to drive the roofing nails into.

Step 5: Roofing

I used corrugated asphalt roofing panels from a company called "Ondura" They measure 6.5 feet by 4 feet and they are very flexible and easy to cut and work with.

Step 6: Gutters, Pipes, Containers

The metal gutters are only needed on the low pitch of the roof. There is a filter in the gutter to keep leaves and debris out of the water. I attached a 3 inch PVC pipe to the downspout of the gutter using a two part epoxy called JB Weld. The PVC pipes direct the gutter water into three water containers. Once the water fills the first container, it will flow up into the pipe to the second container, etc... Each container can hold 255 gallons of water, so all three hold a total of 765 gallons of water. We could continue to add as many containers as we wanted.

Step 7: Collect Free Water!

We will attach irrigation lines to the containers to water our crops this summer. This system could be cheaply and easily replicated anywhere in the world that has a few inches of rainfall, especially in places with no groundwater for a well, or in situations where the cost of drilling a well would be too cost prohibitive.

To prevent algae from growing in the water in the container, just make sure that no sunlight can get in the water by painting the outside of the water container white, or by covering the container with tarps that block light. That being said, I have watered plants with algae water in the past and nothing bad happened, but I wouldn't reccoment it...

Also, it is important to drain the containers during freezing temperatures, otherwise the water will expand and crack the plastic.

Step 8: Download My Free 3D Model to Edit and Build Your Own!

Head over to my website and scroll all the way down for a download link to an editable SketchUp file of this project!

Step 9: Optional: Enclose Walls to Make Greenhouse Nursery

In the future, we would like to enclose the walls. I build the high side facing south, so we could put big windows covering the whole wall to create a greenhouse using transparent plastic roofing panels. The north, east, and west walls can be framed using strong pallets, clad in painted plywood. The inside of the pallets can be stuffed with straw for insulation.



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    14 Discussions

    like comment above check w/city,state,epa...I lived in swfl I moved /owned house/land in more rural area in everglades where it rains almost everyday @3pm . I set up simple water barrels 2 water my plants/vegetables & drip hose bc I'm disabled & allowed me 2 still have a garden...then I get a 10k fine for illegal water collection? wasn't a city law,state but an epa/dfw? said I could interfere w/ecosystem from a 40 gallon tank 2 water plants etc since I can't bend down...lawyer had 2 come & take pics was ok if canoe caught rainwater , boat, buckets even a pick up truck bed w/tarp neighbors used as a pool but not an enclosed filtered system...finally dropped fine after neighbors all parked pick up trucks in my lot w/tarps & hoses having a pool party while I had a orange sticker on water collection w/10k fine ...made the news crap people even sell rain water 2 orchid collectors 2 water ghost orchids from where I live but they didn't want me using rain water.....NTM I was on well water uggg

    I want it in my garden ! Awesome :)


    1 year ago

    After the first few minutes of dirty rain from cleaning the atmospheric pollution and the dust on the roof, rainwater is very clean. Actually, it's distilled water when created.

    Use Ondura corrugated asphalt roofing sheets if you want, but my experience is that they are fragile. Even some of the ones in the stack at Home Depot are damaged on the corners just from being in the store. If the roof it distant from possible tree branch attacks, it will be OK, probably. Despite what the company says (even with a regular roof that has decking beneath), you certainly shouldn't walk on an Ondura panel.

    When I bought Ondura (c. 2000) it was sold with strips (like purlins) of wood that conform to the corrugations. You can see them in this video. The pdf installation instructions don't mention them. They also advise using their own brand of expensive nails that each come with a captured rubber washer.

    I don't have a strong recommendation for the roofing material for rain collection. If the water is just to be as gray-water (watering plants, flushing toilets, etc), any roofing material will work. I suppose translucent fiberglass may be good for a greenhouse.

    1 reply

    We only used Ondura because we are on a tight budget. You're right, Ondura panels are MUCH more fragile compared to metal roofing, and I wouldn't recommend walking on them either. But there aren't any large trees near by, so there's no risk of falling branches.

    This is my first time trying Ondura, and I really feel like this type of roofing is only good for small things like sheds and chicken coops, not a whole house (not even a tiny house)

    In retrospect, I may have been able to save money by just using exterior grade plywood covered with tar-paper as the roofing... It would least be a walkable surface... But this project was just an experiment, and it does what it's supposed to do, irrigate our crops.

    you want to make sure to check all local and state/federal laws if you decide to do this, in some places it is illegal to collect rain water

    1 reply

    We did ask the building department before this build. We showed them my 3D plans and told them that it was specifically for rainwater catchment. They didn't know what to think about it, they just told us that as long as it was under 200 square feet, we wouldn't need a permit. We are in Michigan, and there aren't any draconian water collection laws like in other places.

    Hi, nice design but what about the stored water? It gets bad and smelly in a while, how long it can be safely stored? What if the temperature drops below the freezing point? It will work during the summer months when there is a high demand of water or in areas where there is warm temperature the entire year, otherwise it will have to be dried out once in a while.

    5 replies

    That's totally right, the water can go bad if you don't filter out the leaves and debris before it enters the tank. Otherwise, any organic matter will decompose in the water and it will smell. Also, to prevent algae from growing, just make sure that no sunlight can get in the water by painting the outside of the water container white, or by covering the container with tarps that block light. That being said, I have watered plants with algae water in the past and nothing bad happened, but I wouldn't reccoment it... Also about winter, It is important to drain the containers during freezing temps, otherwise the water will expand and crack the plastic. I will edit the article to include this important information!
    You would usually only be watering plants in spring, summer, and fall,
    though it's a shame not to be able to collect all the snow melt from winter...

    Thanks for sharing experience, i am thinking for a long time to bury the containers under the ground to prevent freezing and collect the water the year round, add a 12v water pump and solar panels, i need it for bathroom and wash dishes as well( not for drinking though) and how long will it stay clean enough this is the only knowledge i am missing. I have the centralized water as well so drinking water is not an issue but i just want to be independent from those guys as much as possible :)

    Smart idea to be more independent from the city water!

    It sounds like what you're talking about is an underground cistern. Here in Michigan, the frost line is 42" deep, but I would probably bury a cistern a little deeper just to be safe! Even if the water is totally clean going into a cistern/tank, it is still a perfect environment for bacteria to grow. According to this article http://www.well-water-report.com/2012/10/how-to-ke... people add a very small amount of chlorine bleach to the water tank to keep bacteria from growing. 4.5 liters (1 gallon) of household laundry bleach (5.25 per cent) for each 4,550 liters (1,000 gal.) of water. I haven't tried this personally because I am afraid it might be bad for our plants. Also, this youtube video has a very detailed explanation of how to filter and purify rainwater that includes an electric UV sterilizing light.

    That might be a bit overkill for us, but this guy wants to be able to drink his rainwater.

    Thanks, bleach is not what i would like to use, probably some tablets instead..the system in the video looks great. I will definitely consider that.

    regarding the leaves and other impurities, i have seen a first level filter sometime ago on the net, maybe you can add it to your system:

    I am not the best image editing guy though.. :D


    Good idea, I should add a first flush diverter for the first couple of gallons of water to clean off the debris from the roof before it even enters the tank. My piping design is really minimalist right now, but I'm researching some other piping designs online for ideas for an upgrade.

    That's a neat setup :) We're putting up a greenhouse later this month and I need to figure out a system that will work for that.

    1 reply

    Is it a glass greenhouse or a plastic hoop house? We have a plastic hoop house, and we are brainstorming ways to collect the rainwater that lands on the hoop house for irrigation.