Jane, your use of the word 'grids' implys that your folks have a multiport, therefore they should be able to vac to 'waste' and avoid 'crudding' up the filter. If there is a problem with fill water, this might not be a good option, but with all the backwashing he must be doing, he's gotta be topping off the pool every other day.
Also, what model filter is it? How many lbs of de are in the box he goes through every other day? The reason I ask is because it sounds like he may be either undercharging the grids (not enough de) or overcharging them (too much de) either of which will reduce the performance of the unit.