The harvesting system is made up of just a few major parts...
- Collection Area
- Gutter System
- 1st Flush Diverter (Roof Washer)
- Holding Tanks
This is simply the roof. My roof is made of asphalt shingles and while this is not good for potable water, it seems to be alright for wash water. I do have plans for a metal roof (Galvalume) but time and finances have dictated that I use what I have for now. There are numerous perceived problems for using an asphalt shingle roof for rain harvesting and I have read conflicting reports pertaining to the safety of water collected from such roofs. Some studies say that the water is no more polluted than that of a wood shingle or metal roof but my gut tells me that I don't want to drink the water from up there so I don't. In any case, all water collected from a roof harvesting system needs to be filtered before drinking..no matter the material.
The gutter system that I installed on my house is very simple. I bought the gutter materiel at Lowes and it simply clicks together. I spent around 50$ and had a few odds and ends left over which I saved for my next project. I have a shed roof with about 1/2 of the length being taken up by an awning. I installed a simple water break over the awning section to mover water down into the gutter which wraps around the side of the house (the shed area) and into a downspout which pours into the first part of my "Roof washer". The inlet here is just a large diameter PVC coupling with a fine mesh screen zip tied to the top of it. An angled setup that automatically rinses debris would be better but......well, hindsight.
1st Flush Diverter
OK. The water coming off your roof is going to be nasty. Bird poop, dead bugs, grit, pollen....all of these things are going to end up in your gutters when it rains and a First Flush Diverter or Roof Washer will help isolate all of these nasties before they hit your cistern. The diverter is simple to make. It is simply a PVC "T" with the top arms going from your gutter system to your cistern or holding tank. The bottom of the T is connected to a reducer fitting (enlarger actually, you want a larger diameter tube at the bottom) and a piece of PVC pipe to match. At the very bottom a matching 90 degree fitting and a threaded cleanout complete the shell. The magic happens inside. In the lower leg (the vertical PVC pipe) you install a rubber ball. As rain comes off the roof it pours into the vertical pipe first and as the water level rises so does the rubber ball. When the vertical pipe is full the rubber ball should be pressing against the top (the backwards reducer) effectively capping the lower pipe and allowing water to freely flow to the outlet which in turn enters your collection tank. There are numerous pictures on the net and this is a really simple project. Here is a list of items that you will need to make one exactly like mine..
- 2" PVC Pipe
- 2" PVC 90 degree (for the inlet from the gutters)
- 2" PVC "T" Fitting
- 2" to 3" (or 4") Reducer
- 3" (or 4") PVC Pipe
- 3" (or 4") 90 degree PVC Bend
- 3" (or 4") Threaded Cleanout
- PVC Purple Primer
- PVC Cement
- Fiberglass Screen (for a sediment filter)
- Large ZIP Ties (to attach sediment filter to the PVC 90 Degree)
- Rubber Ball
I will add some photo's below to try to help explain how to put this together but it's pretty simple and should cost no more than 50-60 $. Or you could buy a pre-made one here.....
You will need to figure out how many gallons you need to flush for the system to work properly as well. My roof is very small, about 200 square feet so I need to only divert the first few gallons of water (2.8 gallons I think). If you have a large roof you may need a bigger system. One option would be to add another washer in series....when the first on fills and lets water pass and the second one starts to work only allowing water to pass after both are filled. There are numerous articles online about how much water to divert but a very safe rule of thumb is 1 gallon per 100 square feet (this is actually overkill a bit). Below is a link to a calculator to figure out the volume of a cylinder. You can use this to determine how much water the vertical PVC pipe will hold....
Don't forget to drill a pinhole in the bottom of the vertical pipe so water will slowly drain out, resetting the system between rain events...
|Simple Sketch of my first flush diverter...don't forget the rubber |
ball inside and the pinhole at the bottom!!
Storing enough water is very important. Obviously. My cistern is a 125 gallon water tank located in a shed on the side of my house. The water enters from a 2" PVC pipe at the top (sealed with silicone) and there is a 1" outlet on the side, about 2" from the top (so really my tank holds about a hundred gallons). This outlet is plumbed back outside to two 35 gallon Rubbermaid brand "Brute" garbage cans which are tied together. These cans also have a small outlet near the top for overflow. I think that using a smaller (1") pipe as an overflow on the main tank was a design flaw but so far it has not rained so hard/much that the overflow could not keep up. It will be interesting to see what happens when I get that much rain though.....maybe have to re-do the overflow. Well, so far so good. A good rain fills the tank and a great rain fills the outside cisterns too. One thing to remember regarding your storage tank. Any light will cause algae growth so an opaque tank is better. My tank is not opaque but I have it housed inside a shed, in darkness. A few drops of bleach will kill algae but keeping the tank out of the sun works too....with no harsh chemicals. I live year round in my tiny cabin so another reason for the tank being inside is to keep it from freezing. This winter I plan to add a small vent and blower and heat the shed as my tank did freeze a couple of times last winter.
I hope this post helps. Collecting water is a neat way to add a little "green" to your house without spending a bunch of green. As water sources dry up and/or get more polluted this may become a necessity. It's nice to be ahead of the curve.
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