Collecting Rain Water

A friend of mine who lives off grid is replacing his current mobile home and building a 2000 sq ft house. The alternitive power system I have installed will handle the home just fine for electrical needs. He would like to collect rain water in large tanks we will put under ground. The water will be used for live stock, washing cars, and garden. Also emergancy back up supply after filtering and treating. I am looking for information on these devices that keep leaves and debri from entering the tank. They also provide a single dump cleaning to clean out bird dropings and insects on the first pail full before the rest of the water from the roof enters the storage tank. Has anyone used these or seen these devices in use. I am shopping for a trouble free system. Also any information on collecting and using rain water for consumption would be helpful. The internet has many but I would like to talk to someone that is using a system currently.

captarcandspark