Goal
Provide instructions for building your own low cost, expandable rain water collection system. The design is built with standard 32 gallon plastic garbage cans, as opposed to expensive, dedicated 55 gallon rain barrels.
Advantages
1. low cost
2. expandable
3. simple break down for temporary storage (transport, seasonality)
4. easy to clean
5. lower maintenance vs. rigid pvc pipe
6. parts readily available
Parts
1. accessible downspout
2. gutter diverter (from Amazon - Oatey 14209 Mystic Rainwater Collection System)
3. water recepticle, such as 32 gallon garbage cans with lids
4. rain barrel fittings (from Amazon - RainPro Solid Brass Rain Barrel Bulkhead Fitting, 3/4 Inch Female Straight Pipe Threaded) - 2 per garbage cans positioned after first garbage can, plus 1 for the first garbage can
5. hose faucet ¾” male threaded
6. flexible hose 1” OD, ¾” ID
7. nylon hose barb adapter (watts A-625) 1” ID x ¾” MIP (from Home Depot)
8. nylon hose barb splicer (watts A-590) ¾” ID x ¾” MIP (from Home Depot)
9. cinder blocks
10. standard 32 gallon plastic garbage cans (trash cans)
Tools
1. knife
2. adjustable wrenches
3. drill with 1 ¼” spade bit (Irwin 88820)
4. hack saw
5. teflon tape
Design Considerations
1. raised height for access and greater pressure difference for low volume applications
2. splicer for easy maintenance and cleaning
3. expandable
4. top cover of input can be moved temporarily
5. visible overflow / movable
6. easy to check collection volumes
7. looks more attractive than pvc setups
8. forego drain installation at bottom (although we lose a little draining height at 3”)
9. connections at bottom to fill in parallel and raise spigot water pressure
Installation Notes
1. cut the downspout at least 2 ft higher than top of collection vessel
2. use cardboard to protect home when you cut the downspout
3. may need to file inside of diverter if you have an older, metal downspout
4. attach all direct plastic adapters to connections to fittings before attaching to garbage cans
5. support both sides when tightening fittings – do not overtighten
6. use care when attaching/detaching hoses
7. be gentle when turning spigot on/off
8. keep lids closed to avoid mosquitos
9. ensure overflow water will not accumulate against your house
Yield and Limitations
I can easily get over 100 gallons from about 500 sq ft portion of the rooftop in a single morning of hard rain. The question is "what can you do with the water?" We have a home with a composite shingle rooftop. The water should not be used for irrigating food crops, as most roofs are built with toxic materials. Even if the water is not in contact with the roof for long, there will still be roofing materials that get dislodged with the rain and will sit in the rain barrels and gutters. So the answer for us is to use the water for ornamental plants only.
If you want to hook the collected water to low volume sprinklers or hand watered applications, you should either position the garbage cans at least 12 feet higher than use level, or invest in a water pump.
IMPORTANT: this system does not use a water tight seal between the lids and garbage cans, Therefore, it is critical that you plan where overflow water will be diverted. I have water drains installed in the alley beside my home. If you do not have such drainage lines installed, be sure to both: a. install the system on a side of your home where the slope is pointed away from your home and b. ensure you are not simply diverting water into your neighbor's property.
General Instructions
1. Measure and confirm your down spout size is compatible with the diverter.
2. Cut and insert the diverter per instructions. I had to file my diverter slightly to fit our old, metal downspouts. I suspect it will fit nicely out of the box for plastic downspouts.
3. Drill a hole in the lid of the garbage can and insert the white tubing. If this is your first time using a bit spade and drill, you will gain confidence with starting on a lid. Drilling holes in the garbage cans is almost as easy - just let the spade bit do the work.
4. You might need to cut excess white tubing slightly, but I recommend keeping at least 1-2 feet extra length in case you wish to reposition the lid onto a secondary garbage can manually.
You can manually test the collection system at this point and get some sense of how much water your rooftop can collect during an average rain. If you wish, you can also simply collect one garbage can at a time, although it is quite possible your garbage can will overflow, in which case you should plan ahead for where this extra water will flow. For example, do you have drainage lines nearby? Is the area immediately surrounding the garbage can slanted away from the house?
I drilled a hole in the bottom of the first collector garbage can and fitted a simple ball valve spigot. Each garbage can should be mounted on cinder blocks for increased water pressure and to allow ample distance for filling portable watering cans and buckets.
Remember, the walls of the garbage cans are relatively thin, so use caution when turning the water on/off. I also recommend greasing the valve every year to ensure smooth operation.
Expanding Your System
Want to collect more water? Expand your first garbage can by drilling on the opposite side and match the depth with an additional garbage can. Install the adapter to the fittings before tightening securely to garbage cans.
Optional: A plastic splicer (shown above connecting two pieces of tubing) was used so I can more easily reposition, disconnect and clean individual cans.
Installing multiple garbage cans will not only increase your collection quantity, but it will also increase the resulting water pressure coming out of your spigot.
The last garbage can in your system should have one adapter at the bottom and one adapter on the opposite side top.
I attach a tube to this last garbage can into an "overflow" garbage can, which allows me the chance to divert water into a final garbage can which I monitor when I am home.
Too Much Water or Preparing for Winter Snow
Again, your system can be completely full in a matter of a few hours, or even a single hour if it's really pouring. You can manually disconnect your system by unplugging the white hose and inserting the red plug which comes with the diverter. I always store the red plug nearby so I can disconnect and reconnect the system as needed.
If you are going out of town or your system is full, use the red plug to disconnect the system. Water from the downspout will travel down through the lower downspout as it did before installation.
If it is the end of the fall season and you need to prepare for winter freezing temperatures, you can disconnect the white tubing and insert the red plug for the winter cold. All garbage cans can be easily disconnected, cleaned and stored for the winter.
Final Thoughts
I hope you enjoyed reading about this expandable, relatively inexpensive design for collecting rain water. I looked at other designs which used PVC tubing inserted at the bottom of each collection vessel. I thought this was a difficult system to build and maintain.
The system above is easy to expand, disassemble and reposition without having to worry about PVC cracking or leaking. Like I mentioned earlier, the next challenge will be finding a way to move the collected water to your garden. Alternatively, with a pump, you might also be able to wash your car at home again.
Please do your best to save the world's precious resources.
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