The filter housing on the AS100 tends to become more difficult to undo and re-tighten as the system ages. To avoid this we suggest lubricating the o-ring every 1-2 years with a food grade lube. (can be purchased from Aqua Safe) This will prevent the 0-ring from gripping to the filter base making it difficult to get undone and difficult to seal when tightening back up. We would also suggest replacing the o-ring every few years to make the yearly service easier as well.
The AS100SL system uses a different all in one filter cartridge and housing making it is very easy to change the filter, does not need lubricating and does not get harder to change with age. This system is purchased by many elderly customers for this reason.