Hello all, I was hoping that you could help me put together the elements of a water reclamation system for my rooftop garden. Here are the specifics:

I have a carriage house in Brooklyn, NY. It has a 1,500 square foot roof. The roof is almost 100% covered with skylights, deck and planters. I'd say it's about 20% skylights, 60% deck, and 20% planters.

(Before anyone brings up a green roof, I went with a decked roof because I have no yard -- this roof is my only outdoor space, so ipe and pavers for me.)

Currently, there's a drip irrigation system that's attached to the city water supply. I, of course, pay for that water... and then pay again as the city charges a sewer charge that's dependent on the amount of water you use.

(This sewer charge galls me because the vast majority of water I use to irrigate never ends up in the sewer.)

Ok, next piece of background is that the drainage for my roof -- both rain and any overflow from the irrigation or occasional hose-watering runs to 2 downspouts and down the back of the house to a concrete paved area between me and the apartment building behind me. It all ends up in a ground drain that I suppose ultimately connects to the city sewer... although it drains so slowly that I think the pipe is collapsed and the water is just absorbed by the ground underneath my building and the building behind me.

So here's what I have in mind.

1. Some tanks or other storage behind my house that hold the water that comes off my roof. I actually have room for quite a few tanks. My land back there is the width of the house -- 50 feet -- and 5' deep. So I could connect up a long series of these tanks and hold a LOT of water.

2. A pump that sends the water back up to the roof whenever the irrigation system calls for water. The pump would have to energy efficient enough that I'm not paying a whole lot more for the electricity than I'm paying for the water. Also, because my house is 2 stories tall, and the area behind the house is down 1 excavated story, the pump will be sending the water up over 30'.

3. Some sort of valve/switch that recognizes when the tanks are empty and sends water from the city water instead.

Lastly, the acquisition and installation cost of the whole system has to be low enough that it pays for itself over a reasonable number of years.

So... any ideas? Anyone want to point me in the right direction or point out the flaws in my design?

Thanks in advance and no suggestion is too out there. Bring it on.