Rain collection system questions for garden irrigation


Old 03-08-10, 02:58 PM
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Rain collection system questions for garden irrigation

Ok, I am planning on installing a series of twenty 50 gallon rain barrels on the flat roof of my mom's garage for a total of 1,000 gallons of storage (it is a 3" thick steel reinforced concrete roof with steel reinforced concrete 'joists' underneath - it can handle the weight). I want to use barrels piped together in order to allow me to spread the weight out rather than having a single tank. I also chose this approach rather than an underground tank, because this is something I can do myself at little cost, without having to replace my lawn. Water rates go up in the summer, and we could be on water restriction at the drop of a hat, so I want to be able to store enough water to sustain her fruit/vegetable gardens and flower beds through possible drought.

Now I have already planned out how I want to plumb the barrels, and I have planned on installing gutter guard, a debris filter, and a first flush filter in the fill line. It will also be set up to automatically divert to the drain field when full, and it will be drained and bypassed during the winter.

My first and most important question, is this "storage tank" will be 13 feet above the ground. Does anyone know if gravity feeding from this height will give enough pressure to feed the sprinkler heads? I will be using 3" pipe to interconnect the barrels, and 2" drop/feeder line, branching off to the individual 1/2" or 3/4" valve controlled garden lines. I would like to do this without a booster pump if at all possible.

Second, for the electric valves, do they require any minimum pressure behind them to operate properly? I would hate to install this and then find the gardens flooded because the valves didn't close.

Does anyone see any potential problems with a setup like this?

Thanks for your input!

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Old 03-09-10, 06:05 AM
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Nope, you will not have enough pressure to run a sprinkler head. You will have less than 6 psi not including pressure loss due to friction in your plumbing. I would use large diameter plumbing to minimize friction loss and use a booster pump to get the water up to a useable pressure.
Old 03-09-10, 01:10 PM
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I am curious how you were able to confirm that the roof will be able to support the additonal 8'500+ pounds of dead load. NJ building codes call for snow loads from 20 to 40 pounds per square foot so it is quite possible you will be within the load limit. I'm just curious how you found the load capacity of your precast roof.
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