If you plumb in a water barrel make sure that it is rated for the water pressure in your area. Otherwise there will be a wet explosion in your basement. None of the plastic water barrels that i know of are rated for pressure. If you put in a pressure tank put a check valve on the inlet side so that if you lose water there will still be pressure in your tank. And hikerdon also mentioned syphon problems so be sure that the vacuum breaker is installed and working on your outside faucet.