The water falls on the roof. The roof has dust and pollen on it. It runs into the rain gutters which have leaf debris and sometimes grass growing in them. It goes down through pipes which have accumulated lots of old black (rotten?) leaf litter in them, and then back up again into the first water tank. The first tank has rotten leaf debris at the bottom (it gets cleaned out about every 7 years), and insects (wood lice) seem to live on the underside of the concrete lid (every time I open it, many fall off into the water to sink and drown).

The water overflows into the next two tanks. Those are for the fire service.

I draw water from the middle of the first tank. It goes through a course filter. Then through a fine filter. Then it comes out my taps.

Water in mountain streams runs through dirt and rotten leaves before it gets to the stream. And most people know that mountain stream water is drinkable.

My neighbor told me that nothing bad lives in the middle. Don't drink off the top, or from the bottom, but from the middle nothing bad lives there.

I've heard stories of people finding dead possums or dead rats in their water tanks. They weren't getting sick from their water, but were disgusted by the finds.

The tanks don't get any sunlight inside of them. The water looks pure. It tastes pure.