Brita system is fine when the sensor light works, which isn't often.  It was never a problem for many years when I started using Brita.  For a number of years now, though, the indicator on the sensor stops working very quickly, so I don't know when to change the filter.  Customer service says not to worry about it, just to change the filter every 4 months.  Maybe so, but why have a sensor/indicator then?