I've been using rainwater for a long time. Back in 2001 we rigged a rain catchment when we were living on a sailboat, and we were hooked. Great tasting water and plenty of it, at least here in the tropics.
We built a house in 2013 with roof runoff collection and a pair of cisterns under the house. A pump at the lower level sent water up to a tank located about 12 meters above the house - so there was always water pressure from that 350 liter reserve. We added a 200L first-flush drum to catch the first debris-laden water draining off the roof.
When we moved in 2021, of course we bought a house with a cistern - but it had no roof drain collection, so we had to retrofit that. The first flush tank is a bit larger now at over 400 liters.
Rainwater from a roof can have bacteria and parasites in it, but during storage, almost everything settles to the bottom of the cistern. One thing that does not is Giardia cysts, so it is wise to filter the water with a one-micron cartridge before drinking. Other household uses are adequately pure after a coarse 50 micron filter at the pump, but the one micron filter is on the cold side at the kitchen sink. The first flush capture and the 50 micron prefiltering are so effective the one micron filter is good for a year or more. Even the 50 micron filter shows no sign of clogging in a year, but when we change it, it LOOKS like it needs changing (very dark brown).
This is a nice informative video. I wish the creator would tell us his qualifications - though at the end he does refer to a source for his ideas - Living Web Farm (which I have not checked out).
He states several times in the video that crushing biochar is detrimental, and maybe he is right. But the high porosity of biochar is a microscopic feature which may or may not be affected by breaking up the char. In the related material, activated carbon, particle size is chosen on the basis of optimizing flow of air or water through the media, not because it has any effect on the capacity of the carbon to adsorb. So put a pin in that point - it may be inaccurate. Big pieces may take longer to adsorb AND release nutrients. The interior of big pieces may not be accessible to plants or fungi (though in the fullness of time the carbon pieces will break smaller and smaller).
Biochar is becoming one of the most common and discussed ways of CDR - it is so accessible to the average person in many variants. I suspect that in the long run, the means of making char will become much more sophisticated and the gas produced by pyrolysis will become a valued product itself - not something that we'd want to burn. But that is for another decade or two . . .