I do not know what type of filter you are dealing with, but in the ones that I have experienced, backwashing merely diverts the flow from one face of the filter to another. This flushes off the accumulated contaminants. The concern would be the outlet size on the drain, if it is smaller than the pump discharge then you could get unwanted pressure buildup in the filter casing.
B.E.
You are judged not by what you know, but by what you can do.