How do I remove chalk stains (washed down from poorly hermetically sealed siding) from brick?
Answers: Powerwash or if you don't have 1 and don't want to rent 1 - travel to Home Depot (or like) and get this screw on attachment for your hose that shoots out a stream of wet at a high pressure, usually loose contained by a bin (it's not packaged) but it works great... usually near where on earth the sprinklers are located...
if it's just chalk after this should wash past its sell-by date easily near water and a devout nylon scrubbing brush.