I vacuum once every two weeks. I usually use the leaf net to grab a lot of stuff off the bottom since it all settles in one of two spots - deep end around drains and nearby the stairs, off to the side of the returns. I will brush towards the drain weekly or bi-weekly as well. (I have plaster so I don't have to be worried about ripping a liner by "skimming" the bottom.) Never vacuumed to waste but then again, I generally clean the pool very well before opening or vacuuming. I have not backwashed yet this season -- been open over a month already.