rain harvesting

Last summer we got a cheap IBC tank for rainwater collection (for veg garden watering). I did a "quick and dirty" hookup as soon as it arrived, so as to not waste the opportunity of a massive downpour due that day. We simply placed the IBC next to an existing water butt fed from a house...

My idea is to have filtered rainwater, pumped from a ground level tank up (8 meters) to the cold water tank in the loft. With the idea of having a raised float system to top the tank up before the mains water float kicks in. Ensuring the inlet for the mains water is above the water line as per...