Gravity aided Catchment tank?

[gtill]

John, as the need for pressure would be intermittant, wouldn't an on demand pump provide the needed occasional use pressure to make everything work. Could be 110AC or 12V battery or both. Could also pump the tank. This would require a little plumbing but would be more water efficient! Remembering the price of hauled water last time, now add fuel adjustments and we know it's goana be dry again! Lets get silly and add "carbon offset" and the world is saved! Cheers!