Some people, mostly plumbers and drillers but homeowners too, don't install a prefilter. I've torn them out and replaced them with a backwashed version.
OK, So "some plumbers, drillers and homeowners" don't install a pre-filter. That just about covers most of the folks installing so who exactly does install a pre-filter. I wish you would stop making blanket statements designed to malign whole groups of people. BTW, I have always installed a pre-filter with and upflow AN filter because the instructions are pretty clear in telling you that you need to so a better statement on your part would be "people that don't read directions don't install a pre-filter" Oh and internet dealers don't install anything.
Good point! To take it a step further, I think a better quote would be "people that don't read directions or understand how it works, shouldn't be installing water treatment equipment at all". Mostly homeowners, not many plumbers or well drillers (who understand that there is dirt & sediment in well water) do this. Also plumbers & well drillers understand the advantage of using an up-flow instead of a back-washing AN unit (when the hardness is low enough that a softener is not needed or wanted) since they don't require water to operate. Anyone who has run their well out of water or had a customer who has, understands this. Remember the summer of 2010? I've had multiple customers whose equipment I've had to bypass until the drought passed so they could have enough water to shower & flush the toilet. Another reason to use (or at least consult with) a local dealer!