The simplest way to do a drainback would be to use gravity to do it. From the drainback systems I've seen it simply requires that you have a tank large enough to hold all the water in the system, then mount the collectors higher than the tank. Set it up with no check valve in the system and no high points in the line where water can collect. All the horizontal lines would need to be mounted at an angle, which would be simple enough to do, you just mount the rack inside the collector at a 10 degree angle. Set the pump to fill the collectors in from the bottom going up, with the hot coming out of the top of the collector. With this setup, when the pump is not running all the water drains back out of the collector and into the heavily insulated tank. There are also several ways you can control the pump so that you don't have to worry about forgetting it, you can do it on a timer, or just direct run the pump from a solar cell, or you can control it with temp senders mounted inside the housing, or even set up a computer with a light/heat sensor that will turn it on and off according to actual conditions instead of a fixed time. This way there's no need for antifreeze, no worries about forgetting.