“We are talking about getting the mesh covers so that the leaves don’t even get into the drains.”
I had to replace a gutter across the edge of the roof over the lower deck so I had a larger gutter than before plus with a mesh screen over it. They are worth their weight in gold as just water goes into the gutter then into a downspout and I have a diverter in that downspout so I can divert it into a 55 gallon water barrel next to the downspout, if I need it. I would let the first dirty water off the roof stay in the downspout to the ground until I thought it was as clean as it was going to get, then divert it into the barrel. I have a Big Berkey water purifier to sanitize that water if I need it. That, of course, is prepper mode.
Yeh, we figured that the rain barrels and swimming pool could do double duty as garden water, or drinking and washing water after treatment. I have a stash of supplies and filtration devices for that.
We also keep 24 gallons of water on hand for short term needs. Then there’s the well, with 2 generators for well power. Last resort: rocket well bucket.