I currently have a DE filter that needs replacing. I'm now considering going to a Pentair Quad DE because it seems to be the best of the cartridge and DE worlds. One thing I'm not clear about is when you know you need to clean or backwash it? Is this still based on the 25% increase in pressure? Many on here say you don't have to backwash it, but I'm unclear what people are doing instead if they're not backwashing.