Myself, I'd probably do a pile of research and end up using a used electric car battery and some cobbled together electronics and it would take me years to get right. It's taken a surprisingly long time to get something as simple as the rain water system right, but I finally have designed a filter that switches to flushing itself clean by reversing the water flow when the tank is full. Just pipes, no electronics. I've been standing there in the rain, watching it work..