California is facing one of its worst drought in record history. The dam that keeps water for most of Northern California (and parts of Southern California) has seen such record lows that a part of California history of the gold rush can be seen.

Now, onto the actual topic. How does one create a loop system for shower/bath greywater usage? I honestly don't know where I got it from (but it ain't the CNN article,) but a guy created his own loop system where when the water drains, it goes back to the heater to be reheated and to be reused. This very idea save him so much that the first month that he began using it, the water company in his area was a bit suspicious with how low his water usage was. I've been trying to find a nice guide for it, but am a bit confused.

The concept is that, instead of wasting shower water that isn't particularly dirty, why not just filter and reuse that water instead?

If anyone is familiar with water-looping and computers, the concept is similar, except that we need to add a filter that cleans the water for reuse.

Here is a simple diagram to show the idea that I want to do, but not sure how to get it done.