I've had the six stage model RCC7P – AK for about a year. I'm just now doing my first filter change, all, but the RO Membrane. I have a bit of an unconventional installation. My system is about 20 feet from the water supply in the sink drain. I've had it installed on the floor. But for this filter change, I mounted it to the wall about 12 inches above the floor with support under the filters. That will make future filter changes much easier in the future. Couldn't be happier with the system. Great system, great tasting water with very effective filtering. My water starts off with a TDS of about 500, water are coming out of the filtered faucet comes in at under 40 TDS :-)