Yes, I admit my comments are more aimed at the theoretical ideal installation. I guess that using these tanks you would have to build an underground enclosure with a concrete load-bearing roof. (not simple or cheap)
Hi,If you are keen to keep the quality of the water as high as possible then excluding light from the tanks will discourage growth of stuff in the water. One effective way of keeping light out is to bury the tanks. Buring the tanks will also keep the water at a more even tempreature. I have read that using copper rainwater goods (gutter and downpipe) helps to sterilise the collected water
Really nice design
Nice instructable. Definitly captures the spirit of the site. I think the three dollars is fair. Cordless drills with clapped out batteries are abundant. I often see them at the tip and usually have one or two lurking around at home. Could always adapt a 12v motor from a car and run on the pc supply.